Search

Climate-driven changes in ocean temperatures, currents, or plankton dynamics may disrupt pelagic forage fish recruitment. Being responsive to such impacts enables fisheries management to ensure continued sustainable harvest of forage species. We conducted a management strategy evaluation to assess the robustness of current and alternative Pacific sardine harvest control rules under a variety of recruitment scenarios representing potential projections of future climate conditions in the California Current. The current environmentally informed control rule modifies the harvest rate for the northern sardine subpopulation based on average sea surface temperatures measured during California Cooperative Oceanic Fisheries Investigations field cruises. This rule prioritizes catch at intermediate biomass levels but may increase variability in catch and closure frequency compared to alternative control rules, especially if recruitment is unrelated to ocean temperatures. Fishing at maximum sustainable yield and using dynamically estimated reference points reduced the frequency of biomass falling below 150 000 mt by up to 17%, while using survey index-based biomass estimates resulted in a 14% higher risk of delayed fishery closure during stock declines than when using assessment-based estimates. [ABSTRACT FROM AUTHOR]

Catch-per-unit-effort (CPUE) standardization in fisheries is a critical foundation for conducting stock assessment and fishery conservation. The Pacific sardine (Sardinops sagax) is one of the economically important fish species in the Northwest Pacific Ocean (NPO). Hence, the importance of choosing an appropriate CPUE standardization model cannot be overstated when it comes to achieving a precise relative abundance index for the efficient management of Pacific sardine fishery. This study's main aim was to assess and compare the efficacy of three models, specifically the General Linear Model (GLM), the Generalized Linear Mixed Model (GLMM), and the spatio-temporal GLMM (VAST), in the CPUE standardization for Pacific sardine fishery in the NPO, with the ultimate goal of identifying the most appropriate model. An influence analysis was applied to analyze the impact of individual variables on the disparity among standardized and nominal CPUE, and the main explanatory variables influencing standardized CPUE were identified. A coefficient–distribution–influence (CDI) plot was generated to analyze the impact of the different models on the annual standardized CPUE. Additionally, a simulation testing framework was developed to evaluate the estimated accuracy of the three models. The results indicated that the standardized CPUE and the nominal CPUE exhibited similar trends between 2014 and 2021 for the three models. Compared to the GLM and the GLMM, the VAST demonstrates larger conditional R2 and smaller conditional AIC, indicating a better performance in standardizing the CPUE for Pacific sardines due to its consideration of spatial and temporal variations. The interaction terms within the three models exert significant influences on the annual standardized CPUE, necessitating their inclusion in the model construction. CDI plots indicate that the spatio-temporal influence of the VAST model exhibits a smaller variation trend, suggesting that the VAST is more robust when standardizing the CPUE for Pacific sardines. Simulation testing additionally demonstrated that the VAST model displays smaller model root mean squared error (RMSE) and bias, establishing it as the superior performer for standardizing CPUE. Our results provide a theoretical basis for the scientific management of Pacific sardines in the NPO and can be extended to CPUE standardization for other small pelagic fish species worldwide. [ABSTRACT FROM AUTHOR]

Pacific sardine (Sardinops sagax) is a commercially important species and supports important fisheries in the Northwest Pacific Ocean (NPO). Understanding the habitat distribution patterns of Pacific sardine is of great significance for fishing ground prediction and stock management. In this study, both single-algorithm and ensemble distribution models were established through the Biomod2 package for Pacific sardine by combining the species occurrence data, sea surface temperature (SST), sea surface height (SSH), sea surface salinity (SSS) and chlorophyll-a concentration (Chla) in the NPO during the main fishing season (June–November) from 2015 to 2020. The results indicated that the key environmental variables affecting the habitat distribution of Pacific sardine were the SSH and SST. The suitable habitat area for Pacific sardine showed significant monthly changes: the suitable habitat range in June was larger than that in July and August, while the suitable habitat range gradually increased from September to November. Furthermore, the monthly geometric centers of habitat suitability index (HSI) for Pacific sardine presented a counterclockwise pattern, gradually moving to the northeast from June, and then turning back to the southwest from August. Compared with single-algorithm models, the ensemble model had higher evaluation metric values and better spatial correspondence between habitat prediction and occurrence records data, which indicated that the ensemble model can provide more accurate prediction and is a promising tool for potential habitat forecasting and resource management. [ABSTRACT FROM AUTHOR]

Otolith analysis allows studying multiple aspects of fish biology, including age estimation; however, otoliths collected from avian stomach content have not been used to estimate the age of ingested fish. We evaluated the potential ability to estimate the age of Pacific sardine (Sardinops sagax) from otoliths collected from blue-footed booby (Sula nebouxii) stomach contents sampled in the Galapagos Islands. Blue-footed boobies were selected because they mostly forage close to their colony (<100 m) and were, therefore, more likely to have almost intact otoliths. To estimate age, we employed three previously developed methods for otoliths. We then related these estimates to the fish's standard length and compared these relations statistically using the Akaike Information Criterion (AIC) to determine which method was most parsimonious. We collected 32 otoliths in relatively good condition, of which we aged 31 with the surface-reading method, 26 with the otolith weight method, and 29 with the posterior otolith length method. Average ages obtained with the otolith methods were 5.6 ± 1.7 yr (± standard deviation), 5.7 ± 2.0 yr, and 3.9 ± 1.5 yr, respectively. Estimates obtained with the otolith weight method had the highest correlation with standard length and the lowest AIC values of the three suggesting it was the best method for aging. Our results indicate that aging otoliths extracted from bird stomachs are possible; however, their use depends on the availability of previously developed methods and how digested the fish are when the birds return to the colony. [ABSTRACT FROM AUTHOR]

Spatial variability in phenotypic characteristics within a fish population may be used to infer the existence of multiple stocks, and knowledge of the population structure of exploited species is important for their sustainable management. In this study we investigated geographic variability in meristic (vertebral count) and morphometric (body shape) characteristics of sardine Sardinops sagax from three southern African regions: Namibia, the South African west coast, and the South African south coast. There were significant regional differences in vertebral counts, with Namibian fish tending to have more vertebrae than South African fish, but with no difference between sardine off the South African west and south coasts. Body shape was characterised using morphometric landmarks, and shape changes were investigated using geometric morphometrics, with influences on fish shape assessed using multivariate regressions. To remove the effects of allometry, the 22 shape variables (represented by Procrustes coordinates) were regressed against fish size (represented by centroid size). There was a significant allometric effect, which was removed by using the residuals of these regressions in further analyses. A multivariate multiple regression was applied to the 22 size-corrected shape variables and to three covariates: condition factor, stomach fullness and fat stage. The significant influence of these covariates was removed by using the residuals from this regression in a canonical variate analysis, where corrected shape variables were classified in relation to region, year and sex. The Mahalanobis distances from the canonical variate analysis differed significantly for most combinations of classifier variables, with clear separations among the three regions. Sardinops sagax off Namibia had thicker bodies and more contracted tail regions than South African fish, whereas S. sagax off the South African south coast had thinner bodies and smaller heads than those off the west coast. These results support the hypothesis of multiple sardine stocks around southern Africa. [ABSTRACT FROM AUTHOR]

Stock level of Japanese sardine (Sardinops melanostictus) was high from 1980s to early 1990s and low from late 1990s to 2000s. The warm and cold water masses in the vicinity of the Kuroshio axis from winter to early spring used to be critical for the recruitment in the high‐stock period, because most of the larvae were distributed there. However, the environmental fluctuation might not affect the recruitment in the low‐stock period. Some studies reported that spawning location and spawning season, and hence the larval habitat, differ depending on the stock level. Three points were investigated in this study: (a) how spawning location and spawning season shifted from the late 1990s, (b) confirmation of the distribution area of larvae in the recent low‐stock period and (c) whether the water temperature in the vicinity of the Kuroshio axis was still related to the recruitment in the low‐stock period. The spawning location and spawning season clearly changed after 1995. Consequently, particle tracking experiments suggested that the larvae appeared in the vicinity of the Kuroshio axis from winter to early spring decreased. Nevertheless, only the ambient temperature of larvae that appeared in the vicinity of the Kuroshio axis from winter had a significant negative correlation with an index of the recruitment in the low‐stock period. It is suggested that the warm and cold masses in the vicinity of the Kuroshio axis are critical for the recruitment regardless of the stock level. [ABSTRACT FROM AUTHOR]

Previous studies have suggested that sardine, Sardinops sagax, off eastern Australia spawns across its entire range when habitat conditions are suitable. However, recent studies have suggested that separate sub‐populations and spawning groups may occur in the region. Spawning patterns off eastern Australia were investigated using data collected during nine ichthyoplankton surveys conducted between 1997–2015, and adult reproductive data obtained from ad hoc commercial sampling off New South Wales (NSW). The egg surveys covered the known distribution of sardine off eastern Australia and included year‐round sampling in the northern and southern parts of this range. Egg distributions and analysis of gonadosomatic indices identified two spatio‐temporally separate spawning groups; one occurring off southern Queensland to northern NSW during late winter and early spring, and a smaller group off eastern Tasmania to southern NSW during summer. Most eggs were collected from waters 50–90 m deep, with sea surface temperatures of 18–23°C. Additive modelling indicated depth was the most significant factor driving selection of spawning habitat, followed by the interaction of month and latitude. Low egg densities were recorded in waters between 34–37°S, despite conditions within the ranges suitable for spawning. The presence of two spawning groups of sardine off eastern Australia supports recent findings that two sub‐populations occur in the region. Findings of this study will help to optimise the spatio‐temporal extent of future egg surveys and further confirm the need to coordinate future management of each sub‐population among relevant jurisdictions. [ABSTRACT FROM AUTHOR]

Abstract Small pelagic fishes such as sardine and anchovy play an important role in marine ecosystem and are affected largely by environmental changes because of their character as r-strategists and their low trophic levels. Small pelagic fishes are crucial targets of Chinese fisheries, accounting for 26% of the total catch in 2014. Their catches show an increasing trend since the 1950s. However, there is still little information on small pelagic species inhabiting Chinese waters. Catch trends and impacts of climatic regime shifts for six typical commercially important small pelagic species, chub mackerel (Scomber japonicus), Japanese scad (Decapterus maruadsi), Pacific herring (Clupea pallasi), Japanese anchovy (Engraulis japonicus), Japanese sardine (Sardinops melanostictus) and horse mackerel (Trachurus japonicus), are analyzed using Chinese Fishery Statistics, FAO data, climatic indices and sea surface temperature (SST) data. The aim is to explore the interannual to decadal variability of their catches in China Seas and their responses to climatic regime shifts. Decadal variability is evident in the catches of the six small pelagic fishes with different variation patterns between warm- and cold-water species. Step changes in catches of the six species were observed in 1976/77, 1986/87, 1995/96, 2001/02 and 2005/06, while regime shifts in climatic/SST indices occurred around 1976/77, the late 1980s and the mid-1990s. This indicates that decadal variations in small pelagic fishes respond strongly to the climatic regime shifts, and the different response patterns of warm- and cold-water species reflect their different life strategies. Marine thermal variation patterns during the period 1981–2000 were well explained by different phase changes in the SSTs between summer and winter and were consistent with the step change in the catches of small pelagic fishes. The double-integration hypothesis, which indicates that cumulative integrations of atmospheric forcing can generate marine population responses, is useful both to understand the process from climate forcing to fish and the controlling mechanism of climate variability on small pelagic fishes in China Seas. [ABSTRACT FROM AUTHOR]

Abstract Small-pelagic fishes are economically and ecologically important as they make up a large proportion of wild-caught fisheries and provide an important link between planktonic organisms and higher trophic level organisms such as piscivorous fishes, squid, seabirds and marine mammals. In the California Current Ecosystem (CCE), the distribution and abundance of Pacific sardine (Sardinops sagax) is influenced by both natural climate variability and exploitation. This study uses Generalized Additive Models to evaluate the effects of environmental forcing at multiple spatial scales (i.e. local, regional and basin) on sardine catch recorded at British Columbia (CAN), California (USA) and Bahía Magdalena (MEX). We find that the Pacific Circulation Index, sea surface temperature, upwelling strength, and primary productivity were the most influential factors explaining variability of sardine catch in the northeastern Pacific Ocean. Our CCE-wide analysis shows that regional scale environmental variability best explained catch rates of the Pacific sardine for California and Bahía Magdalena while basin-scale environmental variability did so for catch rates for British Columbia. [ABSTRACT FROM AUTHOR]

Some studies have characterized and evaluated the parasitic load of the Pacific sardine. However, there are few studies related to its physiology and parasites load. This study aimed to evaluate the blood parameters and the abundance of helminth parasites of sardines obtained from two samples from Todos Santos Bay during autumn 2013. The digenea Myosaccium ecaude parasite was the only species registered. Sardines had a prevalence of 28%, an average abundance of 25 and an intensity of 7 parasites. There were no statistically significant differences (P > 0.05) in most of the analyzed blood parameters (red blood cell count, hematocrit, leukocyte cellular differentiation, mean corpuscular volume, total protein, glucose, alanine aminotransferase, osmotic pressure, Na, K, and pH) of fish with and without parasites, except in white blood cell count and in Ca concentration that showed a marked decrease. The relationship between parasite abundance and blood parameters, based on the results of this study, it is not clear due to the low parasitic load. [ABSTRACT FROM AUTHOR]

Abstract: To evaluate the impact of temporal variation of primary productivity on the recruitment of Japanese sardine (Sardinops melanostictus) in the Sea of Japan, the phenology of sea surface phytoplankton abundance was estimated from 8 day multiple satellite (SeaWiFS, MODIS‐Aqua, MERIS, and VIIRS) derived sea surface chlorophyll (SSChl) a concentrations from January 1998 to December 2015. Because relationships between SSChl a and in situ chlorophyll a concentrations were significantly different among periods based on the satellite combinations used, maximum and minimum SSChl a concentrations of 1 year were relativized as 1 and 0, respectively. Spatio‐temporal variation of relativized SSChl a concentrations was determined by using empirical orthogonal function (EOF) analysis. Scores in the first EOF mode denoted the basin‐scale variations of SSChl a concentrations in the Sea of Japan, and the major peak from the end of February to the end of May displayed the spring bloom. The logarithm of recruitment per spawner (LNRPS) for sardine was positively affected by delays in the start and end dates of the spring phytoplankton bloom. The delay of the date of the lowest sea surface temperature contributed to the delay of the end of the spring bloom during the period 1998–2015 and elevated the LNRPS during the period 1982–2015. Sardine spawns in the southern Sea of Japan from April to May, hence, delays of the spring bloom prolonged its overlap with sardine larval periods, and thus improved the recruitment of Japanese sardine in the Sea of Japan. [ABSTRACT FROM AUTHOR]

The spectral absorbance of photoreceptor visual pigments and the opsin gene class of the visual pigments was investigated in Sardinops melanostictus . Microspectrophotometric (MSP) measurements showed that the rod photoreceptors had peak absorbance spectra (λ max ) at 502 nm. The spectral sensitivity of single cones was centered at 393 nm. Double cones had a λ max of 493/522 nm, but a few displayed a red-shifted absorbance of the long-wave member at 542 nm. The mRNAs of six different opsins were isolated from the retina, retrotranscribed, cloned, and sequenced. Three genes encoded opsins in the green-sensitive class (RH2), and three genes encoded opsins in the red-sensitive class (LWS), the ultraviolet (UV)-sensitive (SWS1) class, and the rod class (RH1). A Southern blot analysis showed that the blue-sensitive (SWS2) opsin gene is absent from this species, hence it was concluded that the λ max of 393 nm was generated from the SWS1 opsin. Phylogenetic analyses of S . melanostictus RH1, LWS, and SWS1 sequences placed them with orthologs from other species (e.g., the cyprinids Danio rerio and Carrasius auratus ) in Otomorpha. However, unexpectedly, the RH2 sequences were more similar to orthologs in members of the Euteleosteomorpha (e.g., Oryzias latipes and Takifugu rubripes ) than to cyprinid RH2 opsins. [ABSTRACT FROM AUTHOR]

A number of ecologically and economically important species in the southern Benguela, including the forage fish sardine Sardinops sagax and anchovy Engraulis encrasicolus, have undergone southward/eastward shifts in their distribution in the 1990s/early 2000s. In addition to the effects of changes in prey availability to top predators, the spatially-distinct nature of the system means the location of a stock has implications for its productivity. The spatial dynamics of small pelagic fish are of particular importance because they are thought to exert wasp-waisted trophic control on the system. An objective-driven frame-based model was constructed to investigate the ability of the approach to represent spatial and population dynamics of sardine and anchovy, and to explore the implications of possible management strategies. Climate variability and fishing pressure were assumed as drivers. Sensitivity analyses were performed and a number of scenarios tested. A frame-based approach appears to be useful within this context. Results suggest that the productivity of the sardine resource within the model is highly dependent on the spatial characteristics of fishing pressure. The role of anchovy within the model system has not yet been fully developed. Increasing our understanding of the relative suitability of environmental conditions of different regions is also important if we are to increase our capacity to predict trends in abundance and distribution. This study shows support for continued careful consideration of spatialized management approaches to the South African sardine fishery. [ABSTRACT FROM AUTHOR]

In the thermal range of the Pacific waters, known for the geographical distribution of Sardinops sagax caeruleus (Jenyns, 1842) (Pacific sardine), could be exposed to a stressing temperature environment with dilated effect. This work examines the liver and kidney of sardines acclimated at different temperatures and exposed to the lethal temperature and critical thermal maximum trials. The liver and kidney tissues of Sardinops sagax caeruleus acclimated for 25 days at 19, 21, 23 and 25 °C were anatomically examined after exposure to acute heat stress (AHS) caused by increasing the water temperature at a rate of 1 °C per min, and the chronic heat stress (CHS) effect by abruptly exposure to constant water temperature different from that of acclimation (AT). We observed in fish exposed to AHS that the liver tissue had vacuolated or necrotic hepatocytes and infiltration of inflammatory blood cells (25 °C) and the kidney tissue showed degenerative changes in the glomeruli and renal tubules and increased melanomacrophage centers. The CHS effect in liver and renal tissues produced damage signs of pyknosis, apoptosis, necrotic areas, and an increase in melanomacrophage centers as well as outbreaks of bacterial infection. The results demonstrate that S. sagax caeruleus did not tolerate an abrupt thermal change of more than 4 °C, independently of the ATs, over 50% died. The consequences of the experimental acute and chronic thermal stress were histopathological alterations of liver and kidney. It was expected that the chronic stress temperature could produce in fish conspicuous histological changes, and indeed it was the most deleterious. [ABSTRACT FROM AUTHOR]

Differences in parasite infection have previously been used to distinguish between fish stocks. We demonstrate a novel use of parasite prevalence-by-length data to inform quantitatively on stock mixing. An initial two mixing stock hypothesis proved consistent with biological and survey data, suggesting that there are different stocks of sardine off the west and south coasts of South Africa. That hypothesis assumed that only recruits moved from the west to the south stock. However, new 'tetracotyle'-type metacercarian parasite bio-tag data indicate a need to allow older fish to move between the stocks as well. We demonstrate extension of bio-tagging to inform on the plausibility of population structure hypotheses by including parasite prevalence-by-length data in the model's likelihood. Our method enables the estimation of the magnitude of mixing between semidiscrete stocks, providing more precise estimates of annual movement. Such improved precision may be important in better informing future movement hypotheses and thereby management. Our research provides a framework to use to inform quantitatively on stock structure and movement hypotheses for other fish species with bio-tagging data. [ABSTRACT FROM AUTHOR]

The North Pacific spiny dogfish (SPD), Squalus suckleyi, is a commercially exploited shark species that plays an important role in the ecosystem. To elucidate the distribution of the SPD in the North Pacific and to evaluate the effects of sea surface temperature (SST) and prey availability on its distribution, we estimated the probability of SPD presence using a generalized additive model with a binomial error distribution from SPD presence/absence data on 14,824 operations in fisheryindependent gillnet surveys between 1972 and 2011. The habitat model was structured in the east and west to reflect differences in the North Pacific oceanic environments. In the east, a higher probability of SPD presence was identified along the coast from the eastern Gulf of Alaska to Queen Charlotte Sound. In the west, it was identified around northern Japan. The estimated distribution was continuous between the two areas, whereas the probability of SPD presence was relatively low. Although the probability of SPD presence was higher at SSTs between 6°C and 12°C, the SST at the peak probability of SPD presence differed between the west and east. The prey species, Japanese sardine, Sardinops melanostictus, and walleye pollock, Gadus chalcogrammus, in the west and boreal clubhook squid, Onychoteuthis borealijaponica, in the east significantly affected the probability of SPD presence, which was higher if the prey species co-existed with SPD. Therefore, SPD might adapt their distribution to that of available prey species. SPD stock assessment and management in these two important areas are required for its sustainable utilization. [ABSTRACT FROM AUTHOR]

Artificial Neural Networks (ANN) are adjusted to predict monthly landings of anchovy (Engraulis ringens) and sardine (Sardinops sagax) in northern Chile (18°21'-24°00'S). Fishing effort (FE), landings and twelve environmental variables are considered from 1980 to 2012. External validation for the best models using all variables showed an R2 of 95% for anchovy and 99% for sardine, with an efficiency of 0.94 and 0.96, respectively. The models were simplified by considering only FE and sea surface temperature (SST) from NOAA satellites (SST-NOAA). Using these variables, very similar fits were achieved, comparing with the previous models, maintaining their predictive capacity. Downscaled SST for A2 climate change scenario (2015-2065) obtained by statistical regionalization from the Community Climate System Model (CCSM3) from National Center for Atmospheric Research (NCAR) and three FE scenarios (2010-2012 average, + 50% and - 50%), were used as inputs for ANN simplified models. For A2 future climate change scenario (2015-2065) using 2010-2012 average FE as inputs, anchovy and sardine landings would increase 2.8% and 19.2% by 2065 respectively. With FE variations (-50%), sardine landings show the highest increase (22.6%) by 2065 when FE is decreased. [ABSTRACT FROM AUTHOR]

Recovery of valuable compounds from by-products generated from seafood processing represents an opportunity to produce value-added products. Sardine acidic proteases were immobilized on partially deacetylated chitin through ionic linkages, using sodium tripolyphosphate as a support activating agent. Maximal enzyme activities of free and immobilized proteases were detected at pH 2, at which the immobilized form had higher stability than the free enzymes. Optimum temperatures for free and immobilized proteases were 40 and 50C, respectively, while thermal stability of immobilized proteases was greater than that of free proteases. Reusability studies showed that after a second catalytic cycle, the immobilized enzyme maintained about 40% of the initial activity. The immobilization process enhanced the long term storage stability of sardine proteases compared to free enzymes. Results suggest that the immobilized enzyme could be used as a biotechnological aid for food processing when low pH and temperature around 50C are needed. Practical Applications Fish waste constitutes a serious environmental problem due to high disposal costs. Besides, this waste is commonly discarded or used for low value processes. Therefore, this study proposes the immobilization of sardine ( Sardinops sagax caerulea) acidic proteases from fish viscera waste, on a partially deacetylated chitin support extracted from shrimp ( Penaeus spp.) head. This research suggests that seafood protease immobilization onto chitinous supports presents an opportunity to improve the stability of these enzymes and consequently enhance potential application of these valuable biocatalysts as biotechnological aid, mainly for food processing and other value added products. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs) occurrence and assessment of dietary exposure from imported canned sardines ( Sardinops sagax ) commercially marketed in local stores and supermarkets in Nigeria were evaluated for the first time. PAHs determinations were performed using high performance liquid chromatography (HPLC) (Agilent 1290 model) equipped with UV-VIS diodes array detector (DAD) at λ = 210 nm and 214 nm. The percentage recoveries were higher than 96%. The degree of contamination expressed as total concentration of PAH congeners ranged between 2.53 and 35.55 μg kg −1 dry weight (d.w.) at λ = 210 nm, and 1.30 and 27.93 μg kg −1 (d.w.) at λ = 214 nm. The carcinogenic (TEQ BaP ) and mutagenic toxicities (MEQ BaP ) of eight priority PAHs were evaluated. Benzo[a]pyrene, benzo[b]fluoranthene, benzo[k]fluoranthene and indeno[1,2,3-c,d] pyrene contributed significantly to the total carcinogenic equivalents of PAHs. The mutagenic equivalents were largely dominated by chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene and benzo[a]pyrene and indeno[1,2,3-c,d]pyrene equivalence factors. The estimated lifetime average daily dose (LADD), average annual excess risk (A R ), excess cancer rate (ECR), and hazard quotient risk (HQ) were evaluated for adults, children and preteens exposure related risks. The LADD, ECR, A R and HQ of PAHs for carcinogenic and non-carcinogenic risks are relatively higher in preteens than children and adults. [ABSTRACT FROM AUTHOR]

A full-length complementary (c) DNA encoding ultraviolet ( UV)-sensitive opsin ( sws1) was isolated from the retina of the Japanese sardine Sardinops melanostictus. The sws1 phylogenetic tree showed a sister group relationship with the Cypriniformes, following the ray-finned fish phylogeny. By expressing reconstituted opsin in vitro, it was determined that the maximum absorbance spectrum ( λmax) of sws1 is around 382 nm, being intermediate in position between two subtypes of sws1 pigment that are UV sensitive ( λmax = 355-380 nm) and violet sensitive ( λmax = 388-455 nm), which have been reported to date. The ocular media transmitted >20% transmittance of light in the range of 360-600 nm. In situ hybridization analyses revealed that sws1 messenger (m) RNA is localized in a central single cone surrounded by four double cones in a square mosaic. The square mosaic occupies the ventro-temporal quadrant of the retina and the in situ hybridization signals were dominant in this area suggesting that the fish may use UV vision when looking upward. Based on these results, considerable significances of potential UV sensitivity, in relation to characteristic habits of S. melanostictus, are discussed. [ABSTRACT FROM AUTHOR]

The stock structure of small pelagic fishes is difficult to determine due to their patchy distribution and complex movement patterns. We integrate genetic, morphological, otolith, growth, reproductive and fishery data collected over 60 years using a Stock Differentiation Index (SDI). The absence of strong separation (SDI > 0.66) of most adjacent sub-groups supports the hypothesis that sardine ( Sardinops sagax) in Australian waters is a meta-population, but with effective isolation of at least four stocks: south western coast (off Western Australia); Great Australian Bight and Spencer Gulf; Bass Strait and Port Phillip Bay (off Victoria and Tasmania); and eastern Australia. There is also evidence for sub-division of the stocks off Western Australia and the east coast. We examine age-related and inter-annual patterns of stock structure off South Australia and the east coast through integrated analysis of otolith chemistry and shape data. For the east coast, there were significant differences between northern and southern sub-groups for all three age cohorts examined. Fish were correctly classified to sampling region with a high degree of success (>80%), supporting the sub-division of the east coast stock suggested by the SDI. For South Australia, there were significant differences among two sub-groups for most cohorts examined across two sampling years. However, spatial discriminatory power was poor, with allocation success ranging from 48 to 64%. Results suggest that movements between the two South Australian sub-groups may vary among years, which is consistent with inconclusive SDI (0.5). Integrating historical data using a SDI is suitable for identifying fishery management units. Integrated analysis of otoliths from archival collections is useful for examining temporal variability in stock structure, which is also important for fisheries management. Our findings are relevant to fisheries where sustainability risks are increased by management arrangements based on assumptions that stock structure is absent or stable. [ABSTRACT FROM AUTHOR]

Schools of fish can cause interference for long-range active sonars. The degree of interference depends heavily on the target strengths of the schools. However, there are few measurements and limited modeling of school target strengths in the frequency ranges of these sonars. During the summers of 2009 through 2013, a comprehensive set of measurements of the characteristics of Pacific sardine schools was collected off the west coast of the United States. This data set has enabled model estimates of the target strength distributions of these schools to be made at frequencies between 500 Hz and 10 kHz. This paper describes the sardine school data, its use in the modeling, the modeling procedures, and the target strength distributions obtained. The analysis indicates that, given the rates at which high target strengths occurred at all frequencies of interest, Pacific sardine schools could be a significant source of interference for long-range active sonars operating in their vicinity. [ABSTRACT FROM AUTHOR]

Analysis of fish movements has been an important area of study for fisheries ecology and population dynamics for decades. Pacific sardine, Sardinops sagax, along the west coast of the United States exhibit a well-defined large-scale seasonal migration. Larger and older fish are found in the northern reaches of their range during summer and contract to southerly offshore areas for spawning during spring. Because of the close correlation between fish size and age it has not yet been determined if movements are size- or age-based. Measuring spatial changes in the age structure conditioned on individual lengths was used to determine the roles of age versus length in the seasonal migration. S. sagax have a pattern of increasing age-at-length with seasonal northward movements and offshore movements for spawning. The pattern of increasing age-at-length with distance from the origin eliminates a solely length-based process of movement and supports age-based movement. Patterns in the size and age when fish first show migratory behaviors, coupled with the patterns observed during the spawning season, support a hypothesis that migratory behaviors are linked to age-based ontogenetic changes associated with maturation. [ABSTRACT FROM AUTHOR]

Response surface methodology was employed to optimize the immobilization yield of acidic proteases from Monterey sardine (Sardinops sagax caeurelea) using partially deacetylated chitin as immobilization support. A rotatable central composite design was applied to evaluate the effects of immobilization conditions such as enzyme loading (X1), immobilization pH (X2), and tripolyphosphate concentration (X3) on the immobilization yield. The analysis of variance revealed that the established model was significant (p <0.05), and the adjustment of the quadratic model with the experimental data was satisfactory. Under optimal conditions (X1= 0.05 mg/mL,X2= 3.16, andX3= 0.75%), an immobilization yield of 79.1% was achieved; a value that was in accordance with the predicted one. [ABSTRACT FROM AUTHOR]

An ecosystem approach to forage fish management is required because forage fish support large fisheries, are prey for many valued species in marine food webs, and provide important social and cultural benefits to humans. Complex ecosystem models are often used to evaluate potential ecosystem consequences of forage fish fisheries, but there is seldom sufficient data to parameterize them, and full consideration of uncertainty is impossible. Models of Intermediate Complexity for Ecosystem assessment (MICE) provide a link between full ecosystem models and tactical (usually single-species) models typically used in fisheries management. MICE are ideal tools to form the basis for management strategy evaluations that compare the ability of candidate strategies to achieve goals related to target fisheries and broader ecosystem protection objectives. A MICE model is developed for the California Current Ecosystem (CCE) that focuses on the fishery for the northern subpopulation of Pacific sardine ( Sardinops sajax ) and the indirect impacts of the fishery on place-based predators, in particular brown pelicans ( Pelecanus occidentalis ) and California sea lions ( Zalophus californianus ), in the Southern California Bight. The model includes three forage species (sardine, northern anchovy Engraulis mordax , and ‘other forage’), an ‘other prey’ category, and two predator species (brown pelican and California sea lion) and evaluates the impacts of variable forage availability on adult predator reproductive success and survival. Parameterization of the model is based on available monitoring data and assessment outputs. The model is used to assess the ecosystem and fishery consequences of the current sardine management systems for Mexico, the USA, and Canada, with a focus on identifying which among a long list of sources of uncertainty in the system are most consequential for predictions of fishery impacts on predators. Key sources of uncertainty to consider in ecosystem assessments for the CCE are how prey abundance and availability impact predator demography and the extent to which the dynamics of prey populations are driven by environmental factors. Data are available for some of these sources of uncertainty for CCE sardine management, but much uncertainty remains, necessitating exploration of sensitivity to alternative model formulations and parameter values when providing advice on management strategies to decision makers. [ABSTRACT FROM AUTHOR]

An excess of low-frequency mutations is a ubiquitous characteristic of many marine species, and may be explained by three hypotheses. First, the demographic expansion hypothesis postulates that many species experienced a post-glacial expansion following a Pleistocene population bottleneck. The second invokes some form of natural selection, such as directional selection and selective sweeps. The third explanation, the reproductive skew hypothesis, postulates that high variation in individual reproductive success in many marine species influences genetic diversity. In this study, we focused on demography and reproductive success and the use of coalescent theory to analyse mitochondrialDNAsequences fromthe Japanese sardine. Our results show that population parameters estimated from both the site-frequency spectrum and the mismatch distribution of pairwise nucleotide differences refute the demographic expansion hypothesis. Further, the observed mismatch distribution, compared with the expectations of the reproductive skew hypothesis, supports the presence of multiple mergers in the genealogy. Many short external branches but few long terminal branches are found in the sardine genealogy. Model misspecification can lead to misleading contemporary and historical estimates of the genetically effective population sizes in marine species. The prevalence of reproductive skew in marine species influences not only the analysis of genetic data but also has ecological implications for understanding variation in reproductive and recruitment patterns in exploited species. [ABSTRACT FROM AUTHOR]

We examined spatial variability in meristic and morphological characteristics of the branchial basket of sardineSardinops sagaxcollected from four geographical regions around the southern African coast, namely Namibia and the South African west, south and east coasts. Our analysis tested the hypothesis of three putative sardine stocks off South Africa, one in each of the three geographical regions. We therefore collected fish data from Namibia to compare with South Africa, because sardine from the two countries are considered to be separate stocks. Morphometric measurements (gill arch length and gill raker spacing) and meristic data (number of gill rakers) were collected from the left side of the first gill arch from a total of 377 sardine, approximately equally divided between the regions. A multivariate general linear model with caudal length as covariate was used to assess differences among fish from the four regions and significant differences were observed, although not always consistently across all fish size classes. Small South Coast sardine had shorter gill arches than small West Coast sardine, but adults had gill arches of similar length, longer than those from Namibia and the East Coast. Small sardine from the South Coast had fewer gill rakers than small sardine from the West Coast, but larger fish had similar numbers of gill rakers, significantly more than sardine from Namibia and the East Coast. Sardine from the West and South coasts had similar gill raker spacings, which were smaller than those of fish from the East Coast and Namibia. Despite spatially and particularly temporally unbalanced sampling, we consider that these differences provide evidence of spatial variation in Benguela sardine phenotype and that it would support the hypothesis of discrete sardine stocks off Namibia and South Africa. The results are consistent with the hypothesis of three sardine stocks within the southern Benguela. [ABSTRACT FROM AUTHOR]

Several commercially and ecologically important species in the southern Benguela have undergone southward and eastward shifts in their distributions over previous decades, most notably the small pelagic fish sardine Sardinops sagax and anchovy Engraulis encrasicolus. Understanding these changes and their implications is essential in implementing an ecosystem approach to fisheries in the southern Benguela and attempting to appreciate the potential impacts of future environmental change. To investigate possible impacts of these shifts at an ecosystem level, distribution maps for before (1985–1991), during (1997–2000) and after (2003–2008) the shift in small pelagic fish were constructed for 14 key species from catch and survey data, and used to calculate spatial indicators including proportion east and west of Cape Agulhas, relative overlap in biomass and area, index of diversity, connectivity. Potential interactions on the south and west coasts were also compared. For several species (redeye; chub mackerel; kingklip; chokka squid; yellowtail), previously unidentified increases in the proportion of biomass east of Cape Agulhas were shown to have occurred over the same period as that of small pelagic fish, although none to the same degree. On average, overlap with small pelagic fish increased over time and overall system connectivity was lowest in the intermediate period, possibly indicating a system under transition. Connectivity declined over time on the west coast while increasing on the east coast. Distributions of other species have changed over time, with the region east of Cape Agulhas becoming increasingly important in terms of potential trophic interaction. Variations in distribution of biomass and structural complexity affect the trophic structure and hence functioning of the system, and implications should be considered when attempting to identify the possible ecosystem impacts of current and future system-level change. [ABSTRACT FROM AUTHOR]

Management strategy evaluation ( MSE) involves using simulation to compare the relative effectiveness for achieving management objectives of different combinations of data collection schemes, methods of analysis and subsequent processes leading to management actions. MSE can be used to identify a 'best' management strategy among a set of candidate strategies, or to determine how well an existing strategy performs. The ability of MSE to facilitate fisheries management achieving its aims depends on how well uncertainty is represented, and how effectively the results of simulations are summarized and presented to the decision-makers. Key challenges for effective use of MSE therefore include characterizing objectives and uncertainty, assigning plausibility ranks to the trials considered, and working with decision-makers to interpret and implement the results of the MSE. This paper explores how MSEs are conducted and characterizes current 'best practice' guidelines, while also indicating whether and how these best practices were applied to two case-studies: the Bering- Chukchi- Beaufort Seas bowhead whales ( Balaena mysticetus; Balaenidae) and the northern subpopulation of Pacific sardine ( Sardinops sagax caerulea; Clupeidae). [ABSTRACT FROM AUTHOR]

Catches of South African sardineSardinops sagaxhave declined in recent years from about 200 000 t harvested annually during the period 2002–2006 to less than 100 000 t. Consequently, some companies are now importing sardine from sources elsewhere in the world to meet local demand for canned sardine and bait. This importation has the potential for the introduction of sardine pathogens, in particular the pilchard herpesvirus (PHV), which could have a negative impact on the currently small South African sardine population. The aims of the current study were to determine whether PHV is present in the local sardine population and to assess the extent to which sardine is being imported into the country and whether imported fish are from countries where the virus is known to be endemic. Fish sampled from South Africa’s western (n= 150), southern (n= 182) and eastern (n= 96) putative stocks ofS. sagaxwere analysed for the presence of PHV using real-time quantitative polymerase chain reaction (qPCR). The origin and amount of potentially infected material imported into South Africa during the period 2010–2014 was also assessed. None of the South African sardine collected during this study tested positive for PHV, suggesting that active PHV was not prevalent in the local population ofS. sagaxat the time of this study. Between 56 000 and 71 000 t of frozen sardine was imported annually into South Africa from countries whereS. sagaxoccurs, including some from areas (Australia and New Zealand) where sardine infection by PHV is known to be endemic. Hence, it is plausible that the PHV pathogen, capable of perpetuating infections in local sardine populations, could be imported into South Africa along with the importation of frozen sardine. Should local sardine be naïve to the virus, as suggested by this study, then the population is at risk of infection and precautions against such must be taken. [ABSTRACT FROM AUTHOR]

Despite the significant advances in making monthly or seasonal forecasts of weather, ocean hypoxia, harmful algal blooms and marine pathogens, few such forecasting efforts have extended to the ecology of upper trophic level marine species. Here, we test our ability to use short-term (up to 9 months) predictions of ocean conditions to create a novel forecast of the spatial distribution of Pacific sardine, Sardinops sagax. Predictions of ocean conditions are derived using the output from the Climate Forecast System (CFS) model downscaled through the Regional Ocean Modeling System (ROMS). Using generalized additive models (GAMs), we estimated significant relationships between sardine presence in a test year (2009) and salinity and temperature. The model, fitted to 2009 data, had a moderate skill [area under the curve (AUC) = 0.67] in predicting 2009 sardine distributions, 5-8 months in advance. Preliminary tests indicate that the model also had the skill to predict sardine presence in August 2013 (AUC = 0.85) and August 2014 (AUC = 0.96), 4-5 months in advance. The approach could be used to provide fishery managers with an early warning of distributional shifts of this species, which migrates from the U.S.-Mexico border to as far north as British Columbia, Canada, in summers with warm water and other favorable ocean conditions. We expect seasonal and monthly forecasts of ocean conditions to be broadly useful for predicting spatial distributions of other pelagic and midwater species. [ABSTRACT FROM AUTHOR]

The historical development of Peru's sardine (Sardinops sagax) fishery between 1978 and 2005 is described from fishery indicators (landings and effort) and environmental indicators (Pacific Decadal Oscillation [PDO] index, Southern Oscillation Index, and Sea Surface Temperature Anomaly) in order to observe the spatial and temporal variations of the fishery. During this period, the fishery indicators showed that excessive fishing pressure caused the drastic decline in abundance, as demonstrated by the low catch levels in recent years. Regarding the environmental indicators, a positive relationship with sardine landing anomalies was observed; however, the PDO index had a significant positive correlation (rPearson = 0.50; P = 0.0005; n = 45) in comparison with the other indices. The results of this study show that the effects of overfishing and adverse environmental conditions strongly impacted the Peruvian sardine population, with the consequent collapse of the fishery. Se describe el desarrollo histórico de la pesquería de la sardina Sardinops sagax en el Perú entre los años 1978 y 2005 a partir de indicadores pesqueros (desembarques y esfuerzo) e indicadores ambientales (Índice de Oscilación Decadal del Pacífico [IODP], Índice de Oscilación del Sur y Anomalías de la Temperatura Superficial del Mar) con la finalidad de observar variaciones espaciotemporales de la pesquería. Durante este periodo, los indicadores pesqueros demostraron que la excesiva presión de pesca sobre este recurso propició la drástica disminución de la abundancia, lo cual se reflejó en los bajos niveles de captura en los últimos años. Respecto a los indicadores ambientales, se observó una relación positiva con las anomalías de desembarque de sardina; el IODP presentó la mejor correlación positiva (rPearson = 0.50; P = 0.0005; n = 45) en comparación con los otros índices. Los resultados de este estudio muestran que el efecto de la intensa actividad extractiva y las condiciones ambientales adversas impactaron fuertemente en la población de sardina, con el consiguiente colapso de su pesquería. [ABSTRACT FROM AUTHOR]

Whether fluctuation in density influenced the growth and maturation variables of three aggregated cohorts (fish born during the 1986-1993, 1996-2003 and 2004-2008 periods) of Pacific sardine Sardinops sagax caeruleus collected off the Californian coast from 2004 to 2010 was investigated. Using a von Bertalanffy mixed-effects model with aggregated cohorts as covariates, estimated growth rate significantly covaried with aggregated cohorts. Growth rate ( K) was modelled as a fixed effect and estimated to be 0·264 ± 0·015 (± s.e). Statistical contrasts among aggregated cohorts showed that the 1996-2003 cohorts had a significantly lower growth rate than the other two aggregated cohorts. The theoretical age at length zero ( t0) and the standard length at infinity ( LS ∞) were modelled as random effects, and were estimated to be −2·885 ± 0·259 (± s.e) and 273·13 ± 6·533 mm (± s.e). The relation of ovary-free mass at length was significantly different among the three aggregated cohorts, with the allometric coefficient estimated to be 2·850 ± 0·013 (± s.e) for the S. sagax population. The age-at-length trajectory of S. sagax born between 1986 and 2008 showed strong density dependence effects on somatic growth rates. In contrast to the density-dependent nature of growth, the probability to be mature at-size or at-age was not significantly affected by aggregated cohort density. The size and the age-at-50% maturity were estimated to be 150·92 mm and 0·56 years, respectively. Stock migration, natural fluctuations in biomass and removal of older and larger S. sagax by fishing might have been interplaying factors controlling growth parameters during 1986-2010. [ABSTRACT FROM AUTHOR]

Quantitative methods are needed to evaluate the ecological effects of fishing forage species upon which predators depend. African penguin Spheniscus demersus numbers at the Robben Island colony rose during the 1990s co-incidental with a marked increase in sardine Sardinops sagax and anchovy Engraulis encrasicolus abundances, but decreased appreciably during the 2000s as sardine suffered a series of poor recruitments. A population dynamics model is developed which relates penguin adult annual mortality to local sardine biomass, and is fit to penguin moult counts and re-sightings of tagged penguins. The predator -- prey interaction is best explained by a sardine-penguin mortality relationship with average penguin survival decreasing only when the local sardine biomass is less than approximately one-quarter of the maximum observed. Results suggest that the rapid growth of the colony during the 1990s was driven primarily by immigration. Penguin projections are generated by linking to future sardine abundances predicted under the operational management procedure used to set catch limits for these sardine and anchovy fisheries, and compared with equivalent scenarios without fishing. Results indicate that fishing is likely to have a relatively small impact on penguins, especially when compared with uncertainties that arise from the variable spatial distribution of the sardine population. [ABSTRACT FROM AUTHOR]

The highly productive Gulf of California exhibits high biodiversity and an abundance of small pelagic, schooling fishes, important both to the ecosystem and to fisheries. These fishes show wide fluctuations in abundance due to oceanographic–atmospheric phenomena such as El Niño-Southern Oscillation, constituting a problem for effective fisheries management. In this work we propose several parameters in the diet of three seabird species as useful predictors of the eventual commercial catch per unit effort (CPUE) of Pacific sardine ( Sardinops sagax ) and northern anchovy ( Engraulis mordax ) in the Midriff Island Region of the Gulf of California. We found that seabirds are sensitive to fluctuations in the abundances of these fishes, their proportions in the diet becoming suitable predictors of future commercial CPUE. The precision of our prediction is high because the birds feed on pre-recruit fish, and the time between the sampling of the diets and the initiation of the fishing season is short, minimizing stochastic effects on recruitment and subsequent abundance due to environmental fluctuations. [ABSTRACT FROM AUTHOR]

We simulated transport of Pacific sardine eggs captured offshore of California in spring of 2001–2012 using a regional ocean circulation model. Eggs were assumed to have developed into larvae within a few days and were modeled using five behavioral patterns: passive transport, diel vertical migration, diel vertical migration combined with swimming against the current, diel migration combined with migration toward shore, and diel migration combined with migration toward the best habitat. Simulated larvae with no swimming behavior were advected far offshore to poor habitat where they were unlikely to survive. Diel vertical migration resulted in less offshore transport because larvae were less affected by surface currents during the day. However, in half the years simulated nearly all juveniles were also located in poor habitat by late summer in this scenario. Swimming against the current combined with diel vertical migration resulted in similar transport patterns to the diel-vertical-migration scenario because currents dominated the transport of eggs and small larvae during the spring and early summer. Migration toward shore resulted in a large fraction of juveniles being located in appropriate habitat during late summer in all years. Migration toward the best habitat was the best strategy modeled. This strategy resulted in a slightly greater proportion of larvae being located in appropriate habitat at the end of summer than the swimming-toward-shore scenario, despite the fact that most larvae were located farther offshore. These results suggest that larval sardine might use directed horizontal swimming behavior to remain in suitable habitat conditions. A large fraction of larvae were transported south into Mexican waters by late summer in all five scenarios. Surveying juvenile sardines in fall near the border of the U.S. and Mexico may be an efficient means of estimating recruitment because the advection pattern of eggs and larvae to the south is opposite the adult migration pattern to the north. This pattern may cause juveniles to be spatially segregated from adults at the time they are being recruited. [ABSTRACT FROM AUTHOR]

Forcing factors and mechanisms underlying multidecadal variability in the production of the world’s major fish stocks are one of the great mysteries of the oceans. The Japanese and California sardine are species that exhibit the regime shifts. It is shown in the present work that during two periods of frequent Asian dust events over the last 100 years, sardines on opposite sides of the Pacific Ocean only flourished under a dust-active regime. The earlier such regime that peaked in the 1930s was strong, and it brought synchronous changes in the two species that were linked to the frequency of Asian dust events. However, there is an apparent mismatch in the rise and fall of abundance between the two species in the current dust-active regime. The massive increase in Japanese sardine stock in the 1970s was related to high levels of ocean precipitation and strong winter mixing, whereas the stock collapse since 1988 has been attributed to diminished winter mixing. High levels of ocean precipitation in the western North Pacific effectively cause wet deposition of Asian dust and enhance Japanese sardine stock, whereas it reduces dust flux that can be transported to the eastern North Pacific, delaying the increase of California sardine stock. Analysis further indicates that productivity of Japanese sardine stock is jointly controlled by wet deposition of Asian dust and winter mixing, which supplies macronutrients from depth. California sardine productivity is inversely related to precipitation in the western North Pacific and is positively affected by precipitation off western North America. This indicates that Asian dust influx dominates productivity of the species because of iron-limited ocean productivity in the California sardine ranges. The analysis suggests that dust regime shifts influence shifts in sardine productivity regimes and that iron input from Asian dust during trans-Pacific transport is directly responsible. It appears that in addition to enhancing phytoplankton growth and carbon sinks, atmospheric iron deposition can regulate the production of living ocean resources, which is an extension of Martin’s iron hypothesis. [ABSTRACT FROM AUTHOR]

Spatial and temporal variation in infection of South African sardine, Sardinops sagax , by a metacercarial parasite was examined to test the hypothesis that the South African sardine population comprises multiple stocks. Samples of adult S. sagax were collected monthly from four commercial fishery landing harbours off the west and south coast and three indices of infection (infection prevalence, mean infection intensity and mean parasite abundance) were determined for each sample. Generalized linear models (GLMs) were used to assess the relative importance of putative stock (sardine caught off the west coast were assumed to be from the putative “western” stock whereas those caught off the south coast were assumed to be from the putative “southern” stock), season, year, fish size and all possible two-way interactions, where a binomial distribution was assumed for prevalence and a negative binomial distribution assumed for infection intensity and parasite abundance. The most parsimonious model for each index was selected based on Akaike's Information Criterion, and significant GLMs were derived for all three indices. Putative stock was the most significant contributor to explaining deviance seen in infection intensity and parasite abundance, and was the second most important contributor to explaining deviance seen in infection prevalence, with fish from the putative western stock having significantly ( p < 0.001) higher parasite loads compared to those from the putative southern stock. Temporal variability was also observed, with season and year also contributing significantly to all three models. Despite this temporal variability, the marked spatial difference in the distribution of infection of S. sagax by metacercariae supports the hypothesis of western and southern stocks of sardine off the coast of South Africa. The presence of infected large sardine off the south coast indicates that these putative stocks are not discrete and that some degree of mixing occurs between them, at least from the western to the southern area. [ABSTRACT FROM AUTHOR]

SardineSardinops sagaxdistributed off the west and south coasts of South Africa have traditionally been assumed to comprise a single well-mixed stock for assessment and management purposes. New research, however, lends weight to the possibility of two stocks in this region. A precautionary management approach thus needs to consider the impact of management decisions on the hypothesised two individual stocks as well as on the resource as a whole. As a first step in this process, Bayesian assessments of South African sardine are presented, which compare results for the traditional single-stock hypothesis with those that follow from a new two-mixing-stock hypothesis. Recruits from the west stock are assumed to move to and remain part of the south stock in annual pulses of varying size. This movement is estimated to be appreciable, and to take place from a substantially more productive west stock to the south stock. This immigration makes a greater contribution to the south-stock biomass than do years of above-average south-stock recruitment. Importantly, this two-mixing-stock hypothesis is shown to be consistent with the data available. Further alternative sardine stock-structure hypotheses suggested by the most recent data are discussed. [ABSTRACT FROM AUTHOR]

The poleward flowing East Australian Current (EAC) drives sporadic upwelling, entrains coastal water and forms the western Tasman Front (wTF), creating a mosaic of water types and larval transport routes along south eastern Australia. The spatial distribution, otolith chemistry and growth rates of larval sardine ( Sardinops sagax) were examined to infer spawning location and larval transport. A gradient of increasing larval size from north to south along the shelf was not detected but was evident between the shelf and offshore in the wTF. Here larvae were larger and older. Based on the occurrence of newly hatched larvae, spawning by S. sagax between southern Queensland and mid New South Wales (NSW) was more extensive than previously reported. The otolith chemistry from two wTF larval size classes differed, implying different origins. The otolith chemistry of wTF post-flexion larvae was similar to larvae from northern NSW, whereas wTF flexion larvae were similar to larvae observed nearby from mid-NSW. Two possible larval transport routes, direct and indirect, are inferred from otolith chemistry, current velocities and a previously published particle tracking study. Either larvae from northern NSW were advected south and entrained with younger larvae directly into the wTF, or larvae from a range of shelf regions were advected around the southern edge of an anticyclonic eddy, to join younger larvae directly entrained into the wTF. Based on the co-occurrence of larval ages and sizes in the wTF and their advection routes, the wTF appears to be an important larval retention zone. [ABSTRACT FROM AUTHOR]

Abstract: Modeling selectivity, the relative capture probability expressed as a function of fish age or length, in statistical catch-at-age models remains one of the most influential and uncertain parameterizations in developing robust stock assessments to provide resource management advice. Selectivity parameterization affects point estimates of management quantities and associated uncertainty, as well as the estimation of other model parameters, such as fishing and natural mortality, growth, recruitment, and spawner–recruit relationships. The choice of biological data (length or age) and selectivity assumptions (length- or age-based) made by assessment analysts can directly impact final estimates of important management quantities. In this paper, Pacific mackerel and Pacific sardine stock assessments based on the integrated age-structured Stock Synthesis model are used in concert with simulation methods to evaluate the influence such decisions have on the quality (bias and precision) of estimates of maximum sustainable yield, current spawning stock biomass, and depletion. Findings from this evaluation indicate that: (1) when age data are used, the selectivity assumption (length- or age-based) was generally less influential and did not impact the quality of derived management quantities; (2) when length data are used, misspecification of selectivity generally produced more variable findings and lower quality estimates for quantities of maximum sustainable yield and current biomass; (3) estimates of depletion were generally more robust and precise, irrespective of the biological data or selectivity assumption used in the model; and (4) formal examination of selectivity as illustrated in this paper is useful for identifying other parameters potentially misspecified in the overall model. [Copyright &y& Elsevier]

Miller, E.F., 2014. Description of conditions preceding the 2011 Redondo Beach, California, fish kill. On 8 March 2011, hypoxic conditions resulted in the loss of ca. 1.5 million Sardinops sagax in King Harbor, Redondo Beach, California. Uncertainty remains regarding the school's entrance into the harbor and the hydrographic conditions leading up to the event. Unusually depressed dissolved oxygen concentrations and acidic pH at 4-7 m depth in the main channel of the harbor were recorded on February 22 during permit-required power plant discharge monitoring. Similarly minimal tidal amplitude occurred on 22 February and 8 March, resulting in minimal seawater exchange within the harbor. Power plant impingement surveys at the nearby generating station began observing S. sagax in January, with an order of magnitude more individuals impinged on 3 February than any prior 24-hour survey and continued impingement occurring at above average levels through February. The data suggested the school entered in late January and might have remained through February at depth. When the 8 March neap tide occurred, hypoxic conditions developed in Basin 1, the most secluded basin, leading to the fish kill. [ABSTRACT FROM AUTHOR]

Highlights: [•] Temperature history of Pacific sardine was inferred from δ18O in otoliths. [•] Seawater in the Pacific Northwest affected north–south trends of δ18O in juveniles. [•] Inferred temperatures correlated inversely with the age of juveniles within a region. [•] Adults recorded δ18O values reflecting cooler temperatures than juveniles. [•] The results are consistent with a northern stock that mixes during annual migrations. [ABSTRACT FROM AUTHOR]

Highlights: [•] Identifying processes leading to variability in larvae and juvenile fish recruitment. [•] Adaptation of the Eulerian model SEAPODYM to early life stages of small pelagic fish. [•] Parameter estimation in data assimilation framework by using eggs and larvae samples. [•] Application to Peruvian anchovy (Engraulis ringens) and sardine (Sardinops sagax). [Copyright &y& Elsevier]

Patterns in the co-occurrence of small pelagic fish species within single shoals were investigated using data from 6 814 throws of commercial purse-seiners in South Africa. Assuming that the throw composition reflected the true composition of the assemblage, it was shown that: (1) mixed pelagic assemblages were as prevalent as pure shoals; (2) assemblages of anchovyEngraulis encrasicolusand sardineSardinops sagaxexhibited a seasonal distribution pattern; (3) there was a highly skewed species ratio in terms of abundance by mass; and (4) patterns in the size distributions of two-species shoals were complex and dependent on theL∞and the relative abundance of the species concerned. We hypothesise that the observed patterns reflect the ‘net gain of the subordinate’, whereby fish occurring in small numbers are less conspicuous and/or less energetically attractive for potential predators if they are smaller than the dominant component of the school. If the subordinate fish grow larger than the dominant fish, this advantage persists. Potential sources of bias are alluded to but are not considered to have had a major impact on the conclusions reached, although they may form the basis for further work. [ABSTRACT FROM PUBLISHER]

Demer, D. A., and Zwolinski, J. P. 2014. Corroboration and refinement of a method for differentiating landings from two stocks of Pacific sardine (Sardinops sagax) in the California Current. – ICES Journal of Marine Science, 71: 328–335.Efforts to survey, assess and manage Pacific sardine (Sardinops sagax) in the California Current may depend on accurate differentiation of the purported two migrating stocks. The southern stock spans seasonally from southern Baja California, México to Point Conception, California; the northern stock spans seasonally from Punta Eugenia, México northwards to southern Alaska. Their seasonal north–south migrations are approximately synchronous within their respective domains, resulting in segregated spawning and different identities. A decade ago, a practical method was proposed for differentiating landings from the two stocks using concomitant measurements of sea-surface temperature (SST). Here, we corroborate and refine the method using regional indices of optimal and good potential habitat for the northern stock, and SST-based indices associated with the 99.9 and 100% confidence intervals of the potential habitat. For months when the index is <0.5, (i.e. when the minority of a fishing region probably includes potential northern stock habitat), the landings are attributed to the southern stock, and vice versa. We applied this method to regional monthly landings data from 2006–2011 and the results indicated that an average of 63–72 and 32–36% of the summertime landings at Ensenada, México and San Pedro, southern California were probably from the southern stock, respectively, depending on the index used. Allocation error could be reduced if the landings were evaluated on finer spatio-temporal scales, particularly during habitat-transition periods. Our method may be used to improve estimates of northern stock biomass, spatial and length distributions, recruitment, and mortality. [ABSTRACT FROM PUBLISHER]

Yasue, N., Doiuchi R., and Takasuka, A. 2013. Trophodynamic similarities of three sympatric clupeoid species throughout their life histories in the Kii Channel as revealed by stable isotope approach. – ICES Journal of Marine Science, 71: .Trophic similarity/difference among multispecies pelagic fish is a focal point in understanding the processes of climate impacts on their population dynamics. We tested trophic overlap of Japanese anchovy Engraulis japonicus, Japanese sardine Sardinops melanostictus, and Pacific round herring Etrumeus teres in the Kii Channel, Japan, by comparing the carbon and nitrogen stable isotope ratios among these clupeoid species from the larval to adult stages throughout the year. Space and time were both significant factors of variations of the isotopic composition values for the three species, and fish size was also significant for sardine and round herring. The isotopic composition values of the three species were homogeneous when compared with those of plankton and some other non-clupeoid species. Moreover, the isotopic composition values of the three clupeoid species collected simultaneously showed closer similarities than those in different areas and dates in all life stages. Thus, spatial and temporal differences in food availability were more apparent compared with interspecific differences in prey items specific to each species. Our analysis indicated strong trophic overlaps throughout the life histories among the three clupeoid species. Hence, they are concluded to be ecologically congeneric (directly competing) species in terms of trophic positions in the pelagic ecosystem. [ABSTRACT FROM PUBLISHER]

Growth rates of round herring Etrumeus teres, Japanese anchovy Engraulis japonicus, and Japanese sardine Sardinops melanostictus larvae respond differently to seasonal temperature variations in Sagami Bay on the Pacific coast of central Japan. Larvae of these three clupeoid species were collected from small seine net catches between February 2008 and April 2009. Correlations between otolith growth increment widths and ambient temperatures were examined at five body sizes and indexed to otolith radii of 50-175 μm, which corresponded to notochord lengths of 15-24 mm. Round herring larvae showed positive correlations between growth rate and habitat temperature at all five body sizes. In contrast, Japanese sardine larvae did not show significant correlations between growth rate and ambient temperature at any of the five body sizes. Japanese anchovy larvae showed significant but weaker correlations between growth rate and temperature than round herring. Although these three species share habitats with some differences in seasonal occurrence in the bay, they showed different species-specific responses to seasonal habitat temperature variations. These differences in response to temperature variations may constitute an ecological basis for different migration patterns among the three species. [ABSTRACT FROM AUTHOR]

Stock discrimination in fishes is important for fisheries management. Morphometric analysis has been a viable approach when different structures (overall body, otoliths, and scales) are used. However, in cases where a single source of information may already differentiate among stocks, different conclusions may be obtained when using different sources of information. These have to be considered because they could lead to different management plans. Using geometric morphometrics, data was analyzed regarding the body and otolith shape of the Pacific sardine Sardinops sagax Jenyns, 1842 collected off the west coast of Baja California Peninsula, Mexico. Results confirm seasonal differences in body shape and otolith shape in stocks previously associated with sea surface temperature. Although both measures resulted in compatible conclusions, the shape of the body discriminated groups more appropriately; the data indicate that differential resolution could be thus obtained, depending on the source of the data. If possible, the application of more than one source of information is suggested in comparable cases because this would detect the extent of stock isolation with greater certainty. [ABSTRACT FROM AUTHOR]