Search

Aquaculture provides an important and expanding source of protein rich and healthy food to the world. However, to minimize environmental harm from aquaculture, interactions with wild fish communities need to be thoroughly assessed. Here, we characterize the existing knowledge pertaining to such interactions, exemplified with Atlantic salmon (Salmo salar) farming in open net pens along the Norwegian coast and potential consequences for wild Atlantic cod (Gadus morhua) populations. Importantly, the wild cod fishery also provides a protein rich, high quality food source with high economic value. We identify seven risk sources that may affect behaviour, physiology, and survival in wild cod. Of particular importance is the large amount of waste feed that causes wild fish to aggregate around farms, thereby altering a multitude of ecological interactions including predation and disease transmission. Moreover, altered food quality in pellets may alter physiological processes and cause mortality to vulnerable life‐stages in wild cod. More research is needed on mechanisms and thresholds for harm. As the most important cod fisheries are found in northern Norway, where climate change also is rapid, we expect stronger and potentially more harmful interactions between fish farming and wild cod fisheries as aquaculture continues to expand. We hope that our analysis will inspire further research, on farmed salmon and wild cod interactions, but also on aquaculture and wild fish interactions in general. Such research is fundamental for the development of management systems that can reduce the impact of aquaculture on fisheries and the environment. [ABSTRACT FROM AUTHOR]

Most stocks of Atlantic cod (Gadus morhua) in the Northwest Atlantic collapsed in the early 1990s, with little sign of recovery since then. In the southern Gulf of St. Lawrence (sGSL), the failed recovery is due to severe increases in the natural mortality of adult Atlantic cod. We examined the role of predation by grey seals (Halichoerus grypus) in this failed recovery by directly incorporating grey seal predation in the population model for Atlantic cod via a functional response. Estimated predation mortality of adult Atlantic cod increased sharply during the cod collapse and has continued to increase, comprising the majority of mortality since the late 1990s. While predation by grey seals appeared to play a minor role in the collapse of Atlantic cod, we found it to be the main factor preventing recovery. Our results are consistent with the hypothesis that failed recovery is due to predation-driven Allee effects, a demographic effect due to the decline in cod abundance and an emergent effect resulting from increasing grey seal abundance. Under current conditions, extirpation of sGSL Atlantic cod appears likely unless there is a large decline in the abundance of grey seals. [ABSTRACT FROM AUTHOR]

Marine protected areas (MPAs) can serve as effective tools for the management and conservation of exploited marine species. The Gilbert Bay MPA in coastal Labrador was created to protect a genetically distinct population of Atlantic cod (Gadus morhua); however, decreases in abundance continue to occur potentially due to exploitation outside the MPA. We developed a single-nucleotide polymorphism (SNP) panel to identify Gilbert Bay cod in areas outside MPA boundaries where mixing with offshore cod occurs. In total, 361 individuals from Gilbert Bay, surrounding areas, and offshore were genotyped for 10 913 SNPs. Using FST rankings and guided regularized random forest, we selected 23 SNPs that together generate 100% accuracy in individual assignment and accurately estimate the proportion of Gilbert Bay cod in fishery samples from sites outside MPA boundaries: on average, fishery samples included 17.3% Gilbert Bay cod. Estimates of effective population size for the Gilbert Bay population ranged from 655 to 1114. Our findings demonstrate the power of using genomic approaches for management of an exploited marine species and enhancing the design of MPAs. [ABSTRACT FROM AUTHOR]

Highlights • Half of the North Sea cod SSB is found in the north-eastern North Sea (1995–2016). • Here we model the dispersal of cod propagules spawned in the north-eastern North Sea. • Results suggests a high degree of spillover of production into the Norwegian Sea. • We predict high survival in Norwegian Sea due to high abundance of C. finmarchicus. Abstract There has been a large-scale geographical re-distribution of the North Sea cod stock over the past century, and recent surveys indicate a north-eastern modal distribution. Here we assess the consequences of the contemporary distribution of North Sea cod (Gadus morhua) spawning biomass to inter-ocean recruitment potential. By simulations of drifting cod eggs and larvae spawned in the northern North Sea over 16 spawning seasons (in the period 1995–2016), we show that a large portion of the North Sea produced pelagic juveniles most likely settle along the Norwegian Sea shelf. For example during the early 2000s when the North Sea cod spawning biomass was at its lowest, 20% to 27% of larvae produced in the northern North Sea most likely settled along the Norwegian Sea shelf, while as few as 8% and 10% were retained within the North Sea in some years. We hypothesise the spillover of North Sea cod into nursery habitat along the Norwegian north-western coast to be beneficial to the stock, as larvae would encounter far higher abundances of their favoured prey, the copepod Calanus finmarchicus. Looking back at a century of overfishing, warming, and variable nursery conditions for cod in the North Sea, getting entrained in the Norwegian coastal current seems like a viable "back-door exit" strategy, allowing the north-eastern spawning cod to thrive even in seemingly adverse climatic periods. [ABSTRACT FROM AUTHOR]

In recent years, Norwegian fishermen have reported problems with fish accumulation in front of the mandatory sorting grids (Sort-X, Sort-V, and Flexigrid). These problems are associated with high fish entry rates and low water flow through the grid sections. In this study, we replaced the lifting panel in the original design of a sorting grid section (Sort-V) by another steel grid (“lower grid”) in order to improve water flow and increase sorting area. Two different inclination angles of this new additional “lower grid” were tested. The results demonstrated that both the lower grid and the main grid contributed to the release of cod and haddock. However, the release efficiency of the lower grid was low compared to that of the main grid. A larger proportion of fish contacted at least one of the grids with the lower grid set at 40° compared to at 35°. The new double grid was found to release significantly more haddock between 38 and 50 cm long than the mandatory Flexigrid. For cod, the sorting system was at least as good as the Flexigrid at releasing undersized fish. Thus, the new double grid system represents a potential alternative to the Flexigrid. Although the Sort-V single grid releases significantly more undersized cod and haddock than the new double grid system, it also releases a significantly higher proportion of the targeted commercial sizes. [ABSTRACT FROM AUTHOR]

Abstract: The Atlantic Cod Gadus morhua population in the Gulf of Maine (GOM) is currently near historically low levels of abundance. Reliable estimates of incidental Atlantic Cod bycatch from Maine's American lobster Homarus americanus fishery, which are unavailable and not included in the current stock assessment, are potentially critical for understanding complete catch dynamics and are thus essential for rebuilding the stock. Available fishery‐dependent data cannot be used directly in estimating Atlantic Cod bycatch because of nonrandom spatial and temporal sampling efforts. We developed a standardized framework for estimating Atlantic Cod bycatch in Maine's inshore lobster fishery for the years 2006–2013. We employed environmental covariates in a bootstrapped generalized additive model framework to standardize monthly zonal Atlantic Cod bycatch per unit effort (BCPUE) and lobster CPUE. Bootstrapped distributions of standardized CPUE and BCPUE were combined with landings data to estimate spatiotemporally explicit confidence intervals of Atlantic Cod discards in the Maine lobster fishery. Modeling results remained consistent throughout the study years, suggesting robustness in our approach. The estimates of Atlantic Cod discards in the lobster fishery improve the understanding of the total GOM Atlantic Cod bycatch and help to address current stock assessment deficiencies. [ABSTRACT FROM AUTHOR]

Shedding rates of tags on fish are commonly estimated from double-tagging experiments, for which an assumption of independence between the two tags on a fish is required. For tags of qualitatively different types, a nonparametric test for this assumption was proposed by Myhre (1966), making use of concurrent double- and single-tagging of fish. We extend Myhre’s test by developing a nonparametric Bayesian test that is also applicable to the common situation where the two tags attached to a fish are identical and assumed to shed at the same rate; the validity of this assumption can be checked by an extra test that we supply in the case that each tag is identified uniquely. In addition to dependence between tags, the dependence test can also be triggered by departures from other experimental assumptions, such as marked variation in the expertise of taggers. We recommend the dependence test for monitoring tag-return data on an ongoing basis during an experiment. We apply our test to Atlantic cod tagging data listed by Barrowman and Myers (1996). Frequentist tests based on Fisher’s Exact Test are also presented. [ABSTRACT FROM AUTHOR]

Archaeological excavations of historical fishing sites across the North Atlantic have recovered high quantities of Atlantic cod (Gadus morhua) bones. In the current study we use Atlantic cod otoliths from archaeological excavations of a historical fishing sites in north-west Iceland, dated to AD 970 –AD 1910 to examine historical growth trajectories of cod. No large scale growth variations or shifts in growth patterns were observed in the current chronologies, supporting the stability of historical Atlantic cod growth trajectories. The most significant variation in growth patterns was consistent with those that have been observed in recent times, for example, reduced early juvenile growth during periods of colder ocean temperature. The current results represent a high resolution chronological record of north-east Atlantic cod growth, greatly increasing the prior temporal range of such data, thereby providing a valuable baseline for a broad range of studies on Atlantic cod growth. [ABSTRACT FROM AUTHOR]

Spatial synchronicity in recruitment was examined for Atlantic cod ( Gadus morhua ) in the Newfoundland and southern Labrador (NL) and Flemish Cap regions. Recruitment was estimated using a cohort strength model for survey indices of abundance at pre-exploitation ages, and spatio-temporal covariation in recruitment was then examined. Patterns of recruitment synchrony were generally consistent with management boundaries. However, there were some exceptions that suggest structure at the sub-stock level and mixing across adjacent stock boundaries. In particular, we observed weak correlations between the eastern and western 3Ps RV (Research Survey) recruitment indices. We also observed strong correlations between the eastern 3Ps RV and the fall and spring 3NO RV recruitment indices, as well as fairly strong correlations between the southern 3L, central 3KL, and 3Ps sentinel GN and LT recruitment indices. Correlations between the summer 3M RV recruitment indices and all other survey recruitment indices included in our analysis were generally very weak, as was expected. We demonstrate that survey recruitment indices can be used to identify either areas of potential sub-stock structure or mixing or areas where recruitment drivers may be operating across or differentially within stock management boundaries. Hence, our results should improve the design of future stock structure research, and provide useful new information for fisheries management. [ABSTRACT FROM AUTHOR]

In land-based fish farms, water quality can be controlled to support maximum growth and good feed conversion. Oxygen is an important water quality parameter in aquaculture and the objective of this study was to detect the range of oxygen saturations that maximizes growth of juvenile Atlantic cod. The fish (initial body mass 21.9 g) were reared at five different levels of oxygen saturation: 65%, 81%, 103%, 121% and 150% of air saturation, for 98 days. At oxygen saturation under 100%, the growth of the fish decreased linearly with progressively lower oxygen saturation with the final body mass of fish reared at 65% saturation being 24% lower than that of fish reared at 103% saturation. The final body mass of fish reared at 150% saturation was significantly higher (7%) than that of fish reared at 103% saturation. Feed intake was also affected by oxygen saturation and was proportional to growth while the feed conversion ratio was not significantly affected by oxygen levels. The results suggest that oxygen saturation of at least 100% is required to obtain maximum growth of juvenile Atlantic cod. [ABSTRACT FROM AUTHOR]

Atlantic cod ( Gadus morhua L.) is one of the most important commercial fish species in Norway and the peak fishing season coincides with spawning from January to April. Live-storage of cod may extend the marketing season for fresh cod products. Cod can be held for up to 12 weeks after capture, and current regulations allow the fish to be held without feeding for four weeks. We investigated whether the response to long-term feed deprivation differed between mature males and females. The fish, caught off Andenes (Norway) in March 2015 using Danish seine, were held without feeding for 82 days, and samples were taken 2, 26, 54 and 82 days after capture. At each sampling, the weights of whole and gutted fish (head on), liver and gonads were measured. Additionally, fillet protein concentrations were analysed. Females lost total weight, gutted weight and liver mass more rapidly than males, but the reduction in gonad mass was significantly higher in males than in females. At termination, after 82 days, fillet protein concentration in males was higher (16.3% ± 0.4) than in females (14.9% ± 0.4). With regard to loss of gutted weight and reduction in muscle protein concentration, the tolerable fasting period of mature spawning Atlantic cod of good biological condition is 54 days, but this can vary depending on upon the initial condition of the fish [ABSTRACT FROM AUTHOR]

A debate has developed over the ecosystem consequences following the collapse of Atlantic cod throughout the coastal waters of eastern Canada. The explosive increase in pelagic fish abundance in scientific bottom-trawl catches on the eastern Scotian Shelf has been interpreted as being due to either ( i) a 'pelagic outburst' of forage fish abundance resulting from predator release or conversely ( ii) a change in pelagic fish vertical distribution leading to a 'suprabenthic habitat occupation' thereby increasing their availability to bottom trawls. These two interpretations have diametrically opposing ecological consequences and suggest different management strategies for these important forage fish species. We argue that an objective evaluation of the available evidence supports the hypothesis that the abundance of forage fish has not increased in response to the demise of cod and other top predators, and the reliance on a single sampling gear with low catchability has biased and will continue to bias the interpretation of demographic trends of pelagic fish populations. We advocate that multiple sampling technologies providing alternative perspectives are needed for the monitoring and management of the various trophic levels if we are to achieve a balanced and objective understanding of marine ecosystems. [ABSTRACT FROM AUTHOR]

The use of triploid fish can potentially reduce two of the major obstacles in Atlantic cod aquaculture; early sexual maturation that causes reduced profitability, and avoiding introgression between farmed cod and native populations, by preventing spawning in the netpens or that escapees reproduce. Cod eggs were pressure treated to produce triploid fish. However, we observed that the pressure treatment produced a mixture of triploid and diploid individuals. The diploid and triploid fish were reared together; in a seawater pond during their larval and juvenile period, and in a commercial cod farm from juveniles to slaughter. Two experiments were performed on two separate year-classes of cod: in the first experiment, fish were reared under artificial continuous light, while in the second experiment the fish were reared under ambient light conditions. Triploid cod had lower gonadosomatic index at all measurements compared to the diploids. However, from a production point of view, triploidisation alone only slightly reduced the gonadosomatic index and had to be combined with traditionally employed artificial light in order to be effective. Triploid fish were generally lighter than the diploids, but this difference disappeared towards time-of-harvest in the year-class without artificial light, possibly because of the lower maturation rate among the triploids. The triploid fish had a higher incidence of skeletal deformities compared to the diploids. Statement of Relevance The use of sterile fish by means of triploidisation is a promising method to reduce sexual maturation and the same time eliminate potential interbreeding of escaped cod with wild cod. In this paper we compare growth, maturation and deformities between triploid and diploid cod reared in common garden under commercial condition. [ABSTRACT FROM AUTHOR]

The flexigrid is a flexible double grid design and is one of the mandatory selection devices used in the Northeast Arctic cod ( Gadus morhua ) and haddock ( Melanogrammus aeglefinus ) fishery. Traditionally the flexigrid is mounted in a two-panel extension section of a trawl just ahead of the codend, but this design has performance limitations, especially during high volume catch situations. The aim of this study was to investigate the size selective properties of a new four-panel section design for the flexigrid and compare them to those of the traditional two-panel section. Specifically, we wanted to determine if this new design would increase the probability for undersized fish to make contact with the grid and subsequently escape through at least one of the two grids in the section. We quantified the parameter “grid contact” for both grids independently and combined for both the mandatory two-panel and the new four-panel designs. We directly compared the two designs using a single trawl with a three compartment experimental design which enabled estimation of the contribution of each of the grids to the combined selectivity of the flexigrid section. The results based on 51 hauls with 108,518 cod and haddock length measurements indicate that the four-panel flexigrid design was better able to release undersized fish than the two-panel design. While the mean values of “grid contact” estimated for both grid designs were similar, the four-panel section had lower risk of clogging in situations of high fish entry rates. Underwater video recordings revealed that the cause for this difference between designs may be related to the difference in shape of the two sections while fishing. The results showed that undersized cod escape mostly through the lower grid of the flexigrid section, whereas haddock generally utilize the upper grid. This finding is in good agreement with the behavioral differences previously described for these two species. Due to the favourable results obtained from this study, the four-panel flexigrid section is now legalized in the Northeast Arctic cod and haddock fishery. [ABSTRACT FROM AUTHOR]

In recent years, the recreational contribution to the total catch of Atlantic cod (Gadus morhua) in the Gulf of Maine (GOM) has increased with recreational discards outnumbering recreational landings by 2:1.However, the discard mortality (DM) rate of cod released in the recreational fishery remains poorly understood, thus contributing to the uncertainty in stock assessments and fishery management plans. The current study examined the capture-related factors most detrimental to codDMin theGOMrecreational rod-and-reel fishery. Atlantic cod (n = 640; 26.0-72.0 cm) were angled from June-October 2013 on southern Jeffreys Ledge in thewesternGOMusing fishing gear representative of the local recreational fishery.A subset (n = 136)was also taggedwith pressure-sensing acoustic transmitters before being releasedinto anacoustic receiver array (n = 31)deployedto monitor survivalupto94days. Toproperly model DMupto the fishery-wide level, all codwere visually assessedforcapture-relatedinjuries accordingto a four-level injury score index. Mean tackle-specific DM rates of 15.4 and 21.2% were estimated for bait- and jig-captured cod, respectively, with an overall 16.5% mean DM rate for the 2013 GOM recreational cod fishery. Twenty-nine cod tagged with acoustic transmitters were identified as dead, where the majority (90%) died within 16 h post-capture. Upon evaluation with a specifically adapted parametric survival analysis, greater incidence of mortality was attributed to the capture and handling process (rather than release) for moderately and severely injured cod. Based on the capture-related factors associated with the highest injury rates, we recommend minimizing fight and handling times, avoiding areas with small cod, educating inexperienced anglers, and favouring bait over jigs to mitigate mortality. Results will continue to inform the development of fishery management plans and enhance survival through dissemination of "best practice" techniques to fishery stakeholders. [ABSTRACT FROM AUTHOR]

Atlantic halibut (Hippoglossus hippoglossus) have a long history of exploitation in the Northwest Atlantic and have gone through several periods of high biomass followed by a population crash. An assessment model using data collected on the Scotian Shelf and southern Grand Banks shows that the population peaked in 1984, then decreased sharply to a low in 1993. Several management measures were taken during the decline, including reductions in total allowable catch and a minimum size limit. Concurrently, removals by the otter trawl fishery were drastically reduced following the collapse of the cod (Gadus morhua) fishery. In 2003, recruitment increased and continued to be high for 6 years. Fishing mortality rates were moderate in the late 1990s and 2000s and the population increased. By 2009, the Atlantic halibut population was highly productive with both high biomass and high levels of recruitment. The coincidence in the timing of population recovery and management actions indicates that effective management contributed to the recovery of Atlantic halibut. [ABSTRACT FROM AUTHOR]

Annual growth zones in cod otoliths from the eastern Baltic stock are less discrete than in other cod stocks leading to biased age reading, which recently led to a failure of age-based assessment in the eastern Baltic cod stock. In this study, we explored the applicability of minor and trace element patterns in cod otoliths for age determination. By first identifying elements of interest in a stock without ageing problems, western Baltic cod, we then tested their applicability on another stock without ageing problems, North Sea cod, and finally applied this knowledge to estimate age of eastern Baltic cod. In western Baltic cod, matching patterns with respect to occurrence of minima and maxima in both otolith opacity and element concentrations were found for Cu, Zn, and Rb, and inverse patterns with Mg and Mn. No match was found for Pb, Ba, and Sr. In the test stock, the North Sea cod, the same patterns in Cu, Zn, Rb, Mg, and Mn signals occurred. All eastern Baltic cod with low visual contrast between growth zones exhibited clearly defined synchronous cycles in Cu, Zn, Rb and Pb. Using a combined finite differencing method and structural break models approach, the statistical significance of the local profile minima were identified, based on which their age could be estimated. Despite extensive environmental differences between the three areas examined, the element concentrations of Cu, Zn, and Rb were strongly correlated in all individuals with similar correlations in all three areas, suggesting that the incorporation mechanisms are the same for these elements and independent of environmental concentrations. [ABSTRACT FROM AUTHOR]

Fish that aggregate at predictable locations and times to spawn are often vulnerable to over-exploitation. Seasonal closures have often been implemented in an attempt to alleviate such impacts but the effectiveness of these measures is rarely tested. This study evaluates the effectiveness of a spawning closure for Atlantic cod (Gadus morhua) in the Firth of Clyde off the Scottish West Coast (ICES Area VIa). This closure was introduced in March 2001 as an emergency measure to allow as many cod as possible to spawn and avoid the build-up of displaced effort from another spawning closure. Genetic, tagging, and otolith microchemistry investigations indicate that cod inhabiting the Clyde are reproductively isolated from other resident groups in the central and northern part of the Scottish WestCoast stock. This study used a beyond-Before-After, Control-Impact approach to compare population trends of the Clyde spawning aggregation before and after the introduced area closure, using two other sub-population spawning grounds as control areas. There was no evidence of local recovery in terms of abundance, biomass, or reduced mortality in the Clyde more than a decade after establishing the closure. Mortality may have remained high because young cod are still caught as bycatch in the Nephrops fishery in the area and the predation rate may have increased due to an expanding whiting population. Considering the state of the already severely depleted Clyde sub-population when the closure was implemented the measure appears to have been too little and too late. The tendency to implement such spawning closures on nearly collapsed stocks may be why these measures often appear to have been ineffective. [ABSTRACT FROM AUTHOR]

Four size groups of juvenile farmed Celtic Sea cod (2.7-41.8 g) were reared at a range of constant temperatures (8-19°C). The optimum temperature for growth ( Topt.G) decreased from 15.1°C for ~3 g fish to 12.5°C for ~42 g fish. A comparison of these results with those published for a more northerly population (Icelandic) suggests that there is no significant difference in the optimal temperature for growth of cod stocks within the size range studied. In contrast, the growth rates of Celtic Sea cod were lower than those derived from these established models (for a northerly stock) for small juveniles (<5 g), but similar for larger fish (>40 g). Thus, while Topt.G appears fixed across the range, there may be high plasticity in local growth performance throughout the Holarctic distribution. Some possible explanations for these differences are considered. [ABSTRACT FROM AUTHOR]

The aquaculture industry supplies coastal waters with large amounts of particulate organic material from the fish cages, which is a source of food for several pelagic and benthic invertebrates and fish. Particularly gadoids, such as cod ( Gadus morhua ) and saithe ( Pollachius virens ), are known to aggregate at fish farms in boreal areas. As a step on the way to investigate the influence of organic fish farm waste on wild fish, we conducted a diet-switch study to determine the extent to which fatty acid composition and stable isotopes (δ 13 C and δ 15 N) of various tissues could be used to trace diet alterations in cod. Initial analysis of the feeds showed that δ 13 C results were non-significant and this tracer was not further pursued. Groups of cultivated cod fry (125–200 g) were fed either salmon feed, herring fillet or cod feed as control feed and sampling was conducted after 26, 41, 69, 106 and 121 days. Fatty acids and stable isotope δ 15 N were analyzed in the various diets and muscle tissue, and δ 15 N was determined in the plasma, liver and heart. All fish groups displayed the fatty acid composition of their diets. The salmon feed group had a significant increase of FAs 18:2n6, 18:3n3 and 18:1n9 by the third sampling (day 69). These FAs are found in rich concentrations in vegetable oils used in salmon feed production. The δ 15 N values showed no significant change in the salmon feed group throughout the experiment whereas the herring group had an increase in all tissues. Linear Discriminant Analysis (LDA) sample distribution plots were identical when FA alone and in combination with the δ 15 N values were analyzed, and both tests correctly classified more than 96% of the samples. Muscle fatty acids were a more precise tracer than δ 15 N since specific FAs could be traced and a combination of fatty acid and stable nitrogen analyses did not improve the robustness of the result. [ABSTRACT FROM AUTHOR]

The article explores the epidemic spread of francisellosis disease, a systemic granulomatous inflammatory disease among Celtic Sea Atlantic cod in the North-East Atlantic region. An overview of commercial fishing of Celtic Sea Atlantic cod fishes in the late 1990s is noted. The Norwegian government has conducted funded projects to breed wild-caught cod broodstock fishes. It also highlights a research study for a vaccine development for treating francisellosis disease among Atlantic cod fishes.

Estimation of proportion mature-at-age is an important component of the estimation of stock productivity. Current methods estimate maturity-at-age in each year or cohort independently. However, cohorts that are alive in the population at the same time are expected to experience similar conditions and therefore have similar maturity trajectories. Methods to take advantage of this information using binomial time series models with over-dispersion are presented to improve the estimation of maturity-at-age, with applications to example populations of Atlantic cod, Gadus morhua Linnaeus, and American plaice, Hippoglossoides platessoides (Fabricius). An auto-correlated beta-binomial model fit the data well compared to other models investigated and improved forecasts of maturities for both populations. Use of an auto-correlated beta-binomial model should lead to improvements in projections of stock status and, hence, improvements in fisheries management advice. [ABSTRACT FROM AUTHOR]

Shifts in the distribution and aggregation patterns of exploited fish populations can affect the behavior and success of fishermen and can complicate the interpretation of fisheries-dependent data. Starting in 2006, coinciding with an increase in sand lance ( Ammodytes spp.) abundance, Gulf of Maine Atlantic cod ( Gadus morhua) concentrated on Stellwagen Bank, a small (405 km2) underwater plateau located in the southwestern portion of the larger (52 461 km2) stock area. The cod fishery in turn concentrated on Stellwagen Bank. Specifically, the proportion of Gulf of Maine cod landings caught in a single 10-minute square area (260 km2) encompassing the tip of Stellwagen Bank increased from 12% in 2005 to 45% in 2010. An increase in landings per unit effort in the fishery coincided with the concentration of the fleet on Stellwagen Bank. Overall, both fisheries-independent and fisheries-dependent data indicate that an increase in sand lance abundance resulted in cod aggregating in a small and predictable area where they were easily caught by the fishery. More broadly, this work illustrates how changes in the distribution patterns of fish and fisherman can decouple trends in abundance and fisheries catch per unit effort. [ABSTRACT FROM AUTHOR]

Atlantic cod (Gadus morhua) has been culturally important in the northeast United States (US) for hundreds of years. This research estimates a hedonic model of cod prices in the Northeast US from 2005-2011. While large fish typically receive premium prices, the largest cod receive prices that are approximately $0.20 per pound lower than fish in the next largest market category. A moderate premium for freshness is found: cod caught on trips that last four days receive $0.04 less per pound than fish that is caught on shorter trips. This discount rises to nearly $0.15 per pound for trips lasting 10 days or longer. A similar discount exists for fish that are stored for two or more days after landing. The premia estimated by the hedonic price model are quite different from the group mean premia, suggesting that bioeconomic models that incorporate price heterogeneity should consider more sophisticated price models. [ABSTRACT FROM AUTHOR]

Individual vessel quotas (IVQs) established on an important target species are a common tool to regulate fisheries. This article investigates fishermen's behavior in a situation in which a primary output quota is decreasing due to policy restrictions. The findings suggest that vessels respond to such situations by increasing pressure on unregulated species, using their spare capacity. This article models fishermen's behavior using a restricted profit function, treating the harvest of regulated species as fixed, while unregulated species are variable outputs. An empirical application is provided for the Polish trawler fleet with permits to harvest IVQ-regulated Atlantic Cod in the Baltic Sea. The results indicate a strong substitute relationship between the cod quota and pelagic species. Derived elasticities of intensity, providing a measure of the impact of a fixed-factor on variable factors, offer strong evidence of increasing pressure on pelagic species caused by decreasing quotas. [ABSTRACT FROM AUTHOR]

The slow recovery of the “northern” Atlantic cod (Gadus morhua) stock off Newfoundland and Labrador has been ascribed to many factors. One hypothesis is poor feeding and condition as a consequence of a decline in capelin (Mallotus villosus), their former main prey. We compared the growth and condition of cod from known inshore (Smith Sound) and offshore (Bonavista Corridor) centres of rebuilding in wild subjects versus captive subjects fed an unlimited diet of oily rich fish. Wild fish in these areas have had different diets and population performance trends since stock declines in the early 1990s. Captive cod from both areas grew at the same rates and achieved equivalent prime condition, while their wild counterparts differed, with smaller sizes, lower condition in small fish, and elevated mortality levels in the offshore centre. Environmental temperature conditions did not account for the differences in performance of wild fish. Our results suggest that fish growth and condition, and hence rebuilding in the formerly large offshore spawning components of the northern cod, have been limited by a lack of capelin in their diet. Furthermore, we suggest that these groups are unlikely to rebuild until a recovery in capelin occurs. [ABSTRACT FROM PUBLISHER]

Many stocks of Atlantic CodGadus morhuahave been depleted due to interactions between overfishing and environmental variation. Stock declines were often accompanied by reductions in spawning diversity and collapses of population structure. Studying Atlantic Cod spawning activity can provide insights into the mechanisms involved in rebuilding. This paper reviews the existing literature on Atlantic Cod spawning dynamics, including habitat, timing, behavior, gamete production, larval survivorship, and fishery impacts. The associated implications for fisheries management are discussed, and critical information gaps are identified for inclusion in future research. Of primary importance for consideration by fisheries managers are the spatial and temporal extent of spawning, the behavior of spawners, and the reproductive contributions of older age-classes. The application of spawning closures as part of a multidisciplinary approach to fisheries management is advocated to prevent the disruption of spawning activity and the extirpation of semidiscrete spawning components. Integrating information on Atlantic Cod spawning dynamics into fisheries management plans will better account for reproductive processes, which is expected to promote rebuilding and decrease the risk of further collapses of population structure. Received August 22, 2013; accepted December 17, 2013 [ABSTRACT FROM AUTHOR]

Lindegren, M., Waldo, S., Nilsson, P. A., Svedäng, H., and Persson, A. 2013. Towards sustainable fisheries of the Öresund cod (Gadus morhua) through sub-stock-specific assessment and management recommendations. – ICES Journal of Marine Science, 70: 1140–1150.Fisheries management traditionally relies on stock assessments assuming discrete populations within large administrational areas. However, failing to account for sub-stock structuring may result in overestimation of the stocks' true harvest potential and unsustainable exploitation of small stock elements. Atlantic cod (Gadus morhua) frequently occurs in spatially segregated populations, some of which exhibit fine-scaled stock structuring within current management boundaries. Here we use the locally spawning cod stock in the Sound (“Öresund”) as a case study, and perform a sub-stock-specific assessment to evaluate biological and economic effects of managing the Sound cod as a separate stock. Our results indicate that reducing exploitation pressure, particularly through technical regulations i.e. increasing gill-net mesh sizes, would not only enhance the stock age distribution, but yield long-term net benefits to the local gill-net fishery. Furthermore, our study emphasizes the need for developing sub-stock-specific management recommendations in order to ensure the maintenance of fisheries resources in general, and the persistence of sub-stock structuring in particular. [ABSTRACT FROM PUBLISHER]

The Northern Cod ( Gadus morhua) fishery supported the removal of approximately 200 000 tonnes per year for centuries until collapse in the late 1980s and closure in 1992. Long recovery times, on the order of a decade or more, are now known to be regular concomitant of steep population declines in fish populations. We investigated reproductive value as an alternative to economic value in assessing fisheries sustainability. Our analysis showed that in cod, price-driven heavy fishing (i.e. fishing mortality positively related to body mass and its dollar value) dramatically impaired reproductive capacity by sacrificing future egg production of large fish. Management based upon current value (either in terms of biomass or equivalently dollar value) substantially underestimates the value of large individuals to the stock; this drove the Northern Cod stock towards collapse by failing to protect individuals with high future value. Our results provide a general explanation for the erosion, collapse and prolonged recovery of a long-lived species where reproductive value increases rapidly with increasing size. Failure to compute and communicate future value relative to current dollar value to resource harvesters leads to unrealistic perceptions of sustainable resource use. [ABSTRACT FROM AUTHOR]

Accurate prediction of species distribution shifts in the face of climate change requires a sound understanding of population diversity and local adaptations. Previous modeling has suggested that global warming will lead to increased abundance of Atlantic cod (Gadus morhua) in the ocean around Greenland, but the dynamics of earlier abundance fluctuations are not well understood. We applied a retrospective spatiotemporal population genomics approach to examine the temporal stability of cod population structure in this region and to search for signatures of divergent selection over a 78-year period spanning major demographic changes. Analyzing >900 gene-associated single nucleotide polymorphisms in 847 individuals, we identified four genetically distinct groups that exhibited varying spatial distributions with considerable overlap and mixture. The genetic composition had remained stable over decades at some spawning grounds, whereas complete population replacement was evident at others. Observations of elevated differentiation in certain genomic regions are consistent with adaptive divergence between the groups, indicating that they may respond differently to environmental variation. Significantly increased temporal changes at a subset of loci also suggest that adaptation may be ongoing. These findings illustrate the power of spatiotemporal population genomics for revealing biocomplexity in both space and time and for informing future fisheries management and conservation efforts. [ABSTRACT FROM AUTHOR]

Enhanced production of high quality and healthy fry is a key target for a successful and competitive expansion of the aquaculture industry. Although large quantities of fish larvae are produced, survival rates are often low or highly variable and growth potential is in most cases not fully exploited, indicating significant gaps in our knowledge concerning optimal nutritional and culture conditions. Understanding the mechanisms that control early development and muscle growth are critical for the identification of time windows in development that introduce growth variation, and improve the viability and quality of juveniles. This literature review of the current state of knowledge aims to provide a framework for a better understanding of fish skeletal muscle ontogeny, and its impact on larval and juvenile quality as broadly defined. It focuses on fundamental biological knowledge relevant to larval phenotype and quality and, in particular, on the factors affecting the development of skeletal muscle. It also discusses the available methodologies to assess growth and larvae/juvenile quality, identifies gaps in knowledge and suggests future research directions. The focus is primarily on the major farmed non-salmonid fish species in Europe that include gilthead sea bream, European sea bass, turbot, Atlantic cod, Senegalese sole and Atlantic halibut. [ABSTRACT FROM AUTHOR]

Over the last decade, the proliferation of social and environmental certification programmes has attracted the attention of a growing number of political scientists interested in new forms of ‘private’ transnational governance. However, we still lack analyses on the nature and extent of different state responses to and involvement in new private transnational governance arrangements in particular sectors and in different jurisdictions. This article advances our understanding of the interactions between nation-state and private transnational modes of governance by analysing the role of national government authorities in Marine Stewardship Council (MSC) fisheries certification in Atlantic Canada, known more for the disastrous collapse of Northern cod stocks than good marine stewardship. Focusing on the 2008 certification of Northern shrimp (Pandalus borealis) fisheries off the Province of Newfoundland and Labrador, the analysis finds that the implementation and maintenance of MSC certification in this case depended on significant support from government authorities. The delicate legitimacy of both authorities faces a period of uncertainty in this case since some certified shrimp stocks appear to be in decline and perhaps also migrating northward off Newfoundland and Labrador. [ABSTRACT FROM PUBLISHER]

Abstract: Variations in life history traits determining reproductive potential of fish stocks are often large enough to invalidate the use of spawning stock biomass (SSB) as an unbiased index of reproductive potential. In northern Gulf of St. Lawrence cod (Gadus morhua), observed annual total egg production (TEP) differed from those estimated based on constant life history traits (i.e. direct proportionality between SSB and TEP). Variability observed in age structure, sex ratio, growth, maturity, and fecundity associated with environmental conditions, exploitation and SSB level clearly demonstrate the highly dynamic nature of TEP and complex interactions between environment, fishing and SSB. The sensitivity of reproductive rate to independent changes of each life history trait was estimated using demographic models. Natural mortality (M) had a larger influence on reproductive rate than variations in growth, maturation and fecundity. Correlations between age structure, growth, reproductive traits, and M demonstrated the importance of including M as a dynamic parameter in the estimation of TEP. TEP should be preferred to SSB as a measure of reproductive potential as, besides providing a means of estimating TEP, the monitoring of life history traits required to estimate TEP will also enable improved tracking of changes in stock productivity and resiliency. [Copyright &y& Elsevier]

Abstract: Sexual maturation patterns of 22 North Atlantic stocks of cod (Gadus morhua) were examined and related to geographical distribution area, ambient water temperature, growth and surplus production. Four patterns were identified, i.e. sexual maturation early in life at small size, early in life at large size, late in life at small size and lastly, late in life at large size. These maturation patterns were geographically clustered and associated with differences in growth and surplus production. Stocks maturing late in life at small size were characterised by slow growth and low surplus production (e.g. stocks in the Gulf of St. Lawrence, Labrador/Newfoundland). Stocks maturing early in life at large size exhibited high to intermediate growth and surplus production (e.g. Celtic Sea, North Sea). Stocks maturing late in life at large size had low to intermediate growth rates and surplus production (e.g. Iceland, North East Arctic), while stocks maturing early in life at small size generally showed intermediate growth and surplus production (e.g. Baltic stocks). Production of recruits per unit biomass showed a latitudinal trend, but appeared largely independent of maturation pattern, growth rate and surplus production. Recruit production of northernmost stocks was lowest and variability highest, mid-latitude stocks exhibited highest productivity and least variability, while stocks at the southern distribution range also showed low productivity. Thus, southern Gulf of St. Lawrence and eastern Scotian Shelf cod maturing late in life at small size with slow growth and low surplus production showed highest recruit production in the Western Atlantic, while the early maturing, fast growing and productive Icelandic and Faroese stocks showed the lowest recruitment production of all Eastern Atlantic stocks. This comparative analysis suggests that maturation patterns relate to growth potential and surplus production whereas annual production of recruits per unit biomass appears unrelated to average size at sexual maturation. [Copyright &y& Elsevier]

Abstract: The purpose of the study was to elucidate whether responses to vibriosis vaccination and gene expressions in parts of the innate immune system were different in families of Atlantic cod (Gadus morhua). The fish were progenies of families with differences in estimated breeding values (EBV) for vibriosis resistance. Families of coastal cod (CC) and northeast Arctic cod (AC) responded well to vaccination with a relative percent survival of 72–95. No correlation between response to vaccination and vibriosis resistance were found (p = 0.146). The AC family with medium low (M) resistance had significant (p ≤ 0.019) lowest mortality among all the unvaccinated fish but the CC-M family. Further, when comparing the vaccinated fish the AC family with very high (VH) resistance had significant (p ≤ 0.004) higher mortality than all except the CC-VL and CC-H families. Parts of the innate immune response were studied by measuring the gene expression of innate immune genes 2 and 4 days post dip vaccination. Vaccinated fish from two families had a weak but significant higher innate immune response compared to control fish of the same family. In vaccinated fish, the gene expression of interleukin (IL) 1b, IL-10, IL-12p40 and hepcidin were significant up-regulated. While, no measureable activations of interferon gamma (IFNγ), IL-8, cathelicidin, LBP/BPI and G-type lysozyme were found. [Copyright &y& Elsevier]

Entanglements of large whales in commercial fisheries in Newfoundland and Labrador, Canada, have been consistently recorded since 1979, as part of a program aimed at releasing captured animals and reducing costs to fishermen. This data set represented an opportunity to identify fisheries posing particular entanglement risks to local whale populations. Data were assessed over the periods 1979-1992 and 1993-2008, corresponding to distinct phases in fisheries distribution and intensity. Between 1979 and 2008, 1,209 large whale entanglements were recorded in Newfoundland and Labrador. These were mostly humpback whales ( Megaptera novaeangliae; 80%) and minke whales ( Balaenoptera acutorostrata; 15%). Dramatic declines in reported inshore whale entanglement rates were observed following the 1992 moratorium on Atlantic cod ( Gadus morhua) fisheries. Recently, more entanglements have been reported further offshore, largely due to expansion of fisheries targeting snow crab ( Chionoecetes opilio). For all whale species, entanglement rates and associated mortality rates varied considerably in different fishing gear. Fractions of humpback and minke whales found dead in different fishing gear differed substantially, with minke whales far more likely to be found dead than humpback whales. [ABSTRACT FROM AUTHOR]

The growth performance of different stocks of farmed North Atlantic cod over several years in Irish rearing conditions is described. The growth trajectories for all stocks reared were similar. From all growth data, it was found that weight at 180 and 365 days post hatch (dph), with mean values of 17.7 and 158.7 g, respectively, are accessible and useful indicators of hatchery growth performance. The importance of using standard benchmarking points to facilitate concerted and improved research efforts is highlighted here. Growth performance was evaluated against existing predictive models and these were found to be quite robust and very useful within certain constraints. Comparative growth modelling using prevailing ambient sea surface temperature regimes for five different countries (Ireland, Norway, Canada, Iceland and the Faeroes) was also undertaken. Harvest size of 2.5 kg was estimated to be reached in approximately 36 months post hatch in the Faeroes, 38 months in Ireland, 37 months in Norway, 40 months for Canada and up to 42 months in Iceland. [ABSTRACT FROM AUTHOR]

Sparrevohn, C. R., and Storr-Paulsen, M. 2012. Using interview-based recall surveys to estimate cod Gadus morhua and eel Anguilla anguilla harvest in Danish recreational fishing. – ICES Journal of Marine Science, 69: 323–330.Marine recreational fishing is a popular outdoor activity in Denmark, practised by both anglers and passive gear fishers. However, the impact on the targeted stocks is unknown, so to estimate the 2009 harvest of cod Gadus morhua and eel Anguilla anguilla, two separate interview-based surveys were initiated and carried out in 2009/2010. The first recall survey exclusively targeted fishers who had been issued with the mandatory Danish fishing licence. The second survey was designed to identify those who fish without a licence. It was estimated that 1231 t of cod were harvested in 2009, corresponding to 4.8% of the entire Danish cod yield (recreational harvest + commercial landings). Area differences were found, and, in certain areas, the recreational harvest of cod accounted for more than 30% of the total yield. The majority (81%) of the recreational cod harvest was taken by anglers. Eels, however, are almost exclusively caught with passive gear (fykenets) and a total of 104 t year−1 was harvested, which corresponds to 19% of the entire Danish eel yield. The inclusion of the harvest taken by fishers without a valid licence was important and added almost 20% to the estimated harvest. [ABSTRACT FROM PUBLISHER]

Uglem, I., Berg, M., Varne, R., Nilsen, R., Mork, J., and Bjørn, P. A. 2011. Discrimination of wild and farmed Atlantic cod (Gadus morhua) based on morphology and scale-circuli pattern. – ICES Journal of Marine Science, 68: 1928–1936.To evaluate the spatio–temporal distribution and ecological impacts of escaped farmed Atlantic cod (Gadus morhua), it is necessary that escapees can be traced in the wild. To do this, simple, reliable, and fast methods for determining the origin of cod are required. The aim of this proof-of-concept study was to evaluate whether simple analyses of scales and body morphology can distinguish between wild and farmed cod. Digital images of fish and scales from adult cod from two farms, and wild cod caught near these farms, were analysed by computer-based image analyses. By combining mean breadth of circuli and length-adjusted scale radius in a discriminant analysis, 86 and 80% of wild and farmed fish, respectively, were correctly classified. Moreover, using three simple morphometric measures representing dorsal fin size, neck curvature, and length of lower jaw, 100 and 95% of wild and farmed cod, respectively, were classified correctly. To validate these discrimination methods further, an expanded analysis of additional farmed and wild cod populations is required. The results pave the way for the development of a reliable and standardized methodology for classification of the origin of cod caught in the wild. [ABSTRACT FROM PUBLISHER]

Biochemical, physical and sensory quality of farmed Atlantic cod subjected to percussion stunning (control), anaesthesia (AQUI-S) and excessive exercise (30 min chasing before slaughter, 'stressed') were analysed after 7 days of ice storage. The white muscle energy status (initial pH, muscle twitches and high-energy phosphates) revealed that the fish were truly representatives of rested (percussion stunned and anaesthetised) and stressed cod. Sensory evaluation showed that the fillets of cod exposed to percussion stunning and AQUI-S anaesthesia prior slaughter had slightly higher whiteness scores, and that the fillets of AQUI-S anaesthetised cod had slightly shinier surfaces than the fillets of cod exposed to pre-slaughter stress. Furthermore, fillets of anaesthetised (AQUI-S) cod had significantly higher inosine monophosphate (IMP) contents and lower K-values than fillets of cod exposed to pre-slaughter stress, after 7 days of ice storage. Pre-slaughter stress did to some extent affect fillet colour immediately after killing and after ice storage. Otherwise, no significant effects of stress were observed with regard to biochemical, physical or sensory quality (ultimate pH, water content, drip loss, water holding capacity, texture and gaping) of farmed Atlantic cod. [ABSTRACT FROM AUTHOR]

The northwest Atlantic has had a notable history of living marine resource (LMR) exploitation. There have been calls for evaluating and improving approaches to manage those resources as stocks have undergone sequential depletion, with some dramatic instances of stock declines. The need for more holistic ecosystem-based approaches to manage LMRs has been increasingly recognized as part of these calls, along with the recognition that there are broader issues to consider when managing a fishery. We discuss some of the major efforts to this end which are extant among our institutions. We emphasize current initiatives to implement ecosystem-based fisheries management in the northwest Atlantic, with a focus on how advice based on the natural sciences supports an ecosystem-based approach. We present this information as a case study within a rich historical context of fisheries science and management. [ABSTRACT FROM AUTHOR]

Bui, A. O. V., Castonguay, M., Ouellet, P., and Sévigny, J-M. 2011. Searching for Atlantic cod (Gadus morhua) spawning sites in the northwest Gulf of St Lawrence (Canada) using molecular techniques. – ICES Journal of Marine Science, 68: 911–918.The overexploitation of Atlantic cod (Gadus morhua) in the Northwest Atlantic led to the collapse of most stocks and the demise of spawning components in the early 1990s. In the northern Gulf of St Lawrence, the spawning component of Northwest Atlantic Fishery Organization Division 4S was believed no longer to exist after the collapse. To verify this hypothesis, we used molecular techniques to identify cod, haddock, and witch flounder (CHW) eggs precisely, in an attempt to locate the potential remaining spawning sites for cod in the northwest Gulf. Ichthyoplankton surveys were conducted in spring from 2005 to 2008. Results were compared with those of surveys that took place in spring in the same area 20 years earlier to determine if there had been any changes in spawning location and egg abundance. Atlantic cod made up the majority (97%) of CHW eggs identified. The presence of stage I cod eggs proved that there is still a cod spawning component in the northwest Gulf of St Lawrence, but egg abundance has declined by about an order of magnitude compared with the 1980s. There was no obvious difference in the location of cod spawning grounds between the two decades. [ABSTRACT FROM PUBLISHER]

Glover, K. A., Dahle, G., and Jørstad, K. E. 2011. Genetic identification of farmed and wild Atlantic cod, Gadus morhua, in coastal Norway. – ICES Journal of Marine Science, 68: 901–910.Each year thousands of Atlantic cod escape from Norwegian fish farms. To investigate the potential for the genetic identification of farmed–escaped cod in the wild, three case studies were examined. Samples of farmed, recaptured farmed escapees, and wild cod were screened for ten microsatellite loci and the Pan I locus. Variable genetic differences were observed among cod sampled from different farms and cages (pairwise FST = 0.0–0.1), and in two of the case studies, the most likely farm(s) of origin for most of the recaptured escapees were identified. In case study 2, wild cod were genetically distinct from both farmed fish (pairwise FST = 0.026–0.06) and recaptured farmed–escaped cod (pairwise FST = 0.029 and 0.039), demonstrating the potential to detect genetic interactions in that fjord. Genetic identification of escapees was more challenging in case study 3, and some morphologically characterized wild cod were found to most likely represent farmed escapees. It is concluded that where cod are farmed in the same region as their own parents/grandparents were initially sourced, or where farmed escapees originate from multiple sources, quantifying genetic interactions with wild populations will be challenging with neutral or nearly neutral markers such as microsatellites. [ABSTRACT FROM PUBLISHER]

The potential effects of handling stress on the product quality of farmed Atlantic cod were studied in a controlled experiment (fish anesthetized with metomidate or isoeugenol, or subjected to stress by chasing for 30 min). For comparison, stress and fillet quality was also studied for commercially slaughtered farmed cod (fish sampled from waiting cage, after pumping and stunning with carbon dioxide, and after bleeding and chilling). Baseline values for stress-related parameters (blood chemistry, muscle high-energy phosphates and inosine monophospate, initial pH, muscle twitches, and rigor mortis) of rested Atlantic cod have been established. Since our stress bout showed that this species was not easily excitable, we were less convinced that we actually did study the other extreme, namely, exhausted fish. Nevertheless, the present data from the commercial slaughter of cod suggested that our stress bout was of adequate magnitude to represent potential poor handling routines. Our results consistently showed largely no differences between treatments, and that perimortem handling stress did not cause inferior flesh quality. This suggested that farmed cod can be processed with little risk of reducing product quality (quality index, fillet water content, water-holding capacity, ultimate pH, adenosine triphosphate-related degradation products and K-value, skin and fillet color, water and salt-soluble proteins, hardness, and gaping). For better maintenance of skin appearance after storage, the importance of storing the gutted cod on the belly, avoiding direct contact between skin and crushed ice, is demonstrated. Baseline (rested) values for Atlantic cod muscle biochemistry have been established. Contrary to observations for a number of other fish species, the present study showed that perimortem stress did not, largely speaking, result in inferior product quality. However, attention to harvesting practices should not be neglected since gentle handling is a prerequisite for good fish welfare. The external appearance (quality index) of the cod after ice storage can be significantly improved if the fish are stored on the belly, avoiding direct contact between skin and ice. [ABSTRACT FROM AUTHOR]

Investigations into the 0-group fish in the Barents Sea have been carried out since 1965, with the goal of estimating the abundance of 0-group fish. 0-group abundance indices have been used in the assessment of the recruitment level and in recruitment variability studies. However, the ecological importance of the 0-group fish in the Barents Sea has been less studied. Although 0-group capelin, herring, cod and haddock are widely distributed in the Barents Sea, the central area seems to be the most important, accounting for approximately 50-80% of the annual biomass. The total biomass of the four most abundant 0-group fish species can be up to 3.3 million tonnes, with an average of 1.3 million tonnes (1993-2009). Wide distribution and high biomass of pelagically distributed 0-group fish make these fishes an important element in the energy transport between different trophic levels and different geographical areas, having a critical impact on the entire Barents Sea ecosystem. In recent years, capelin have shown a pronounced northward shift in biomass distribution, and several successive strong year classes occurred during warm temperature conditions. Cod biomasses were unexpectedly low during warm years and were positively correlated with spawning stock biomass, while the correlation with temperature was not significant. Haddock and herring show, as expected , increasing biomass with increased temperature when the spawning stock is at a sufficiently high level. [ABSTRACT FROM AUTHOR]

Gröger, J. P., and Fogarty, M. J. 2011. Broad-scale climate influences on cod (Gadus morhua) recruitment on Georges Bank. – ICES Journal of Marine Science, 68: .Climatic influences on Georges Bank cod recruitment were investigated using the North Atlantic Oscillation (NAO) as an index of atmospheric variability and the Atlantic Multidecadal Oscillation (AMO) as an index of sea surface temperature. A quantitative approach based on a simple Cushing-type stock–recruitment model was developed and extended to include climate influences using the technique of generalized transfer functions (ARIMAX modelling). This allowed the autoregressive nature of the interacting exogenous and endogenous processes to be taken into account. Based on two information criteria, the resulting best transfer function contains winter NAO with a lag of 3 years, annual AMO with a lag of 1 year (both as exogenous climate factors), loge(spawning-stock biomass) as a structural model component, plus two autoregressive parameters. The model is characterized by the smallest information criteria, 92% of explained recruitment variation (vs. 55% from the simple Cushing-type model), excellent forecasting behaviour, and all model assumptions being fulfilled. It is proposed that the model's recruitment hindcasts (ex post forecasts) and forecasts be incorporated into stock and risk assessments as well as management strategy evaluations, either as a climate-induced recruitment index for projections or as real forecasts to establish sustainable cod fisheries on Georges Bank conditioned by climate as a forcing factor. [ABSTRACT FROM PUBLISHER]

Abstract: Little is known about the size selectivity of cod in static fishing gears such as pots and traps. In this field study, floating fishing pots were equipped with 40, 45 and 50mm square mesh escape windows in order to estimate the size selectivity of cod at different mesh sizes. Relationships between selectivity parameters and mesh size, as well as an optimal mesh size for the escape window with respect to current minimum landing size of cod in the Baltic Sea were sought. The results show that the floating pot is not only species selective when used in the Baltic Sea cod fishery, the implementation of an escape window reduced the proportion of undersized bycatch in the pots by more than 90%. The estimated length at 50% retention was found to be a direct function of fish body length (girth) and mesh size of the escape window, while the estimated selection range remained unchanged regardless of mesh size. Optimal mesh size, with respect to the length at 50% retention and current minimal landing size of 38cm in the Baltic, was determined to be 45mm. Strong indications (significant on the 0.01 probability level in the case of 50 and 40mm escape windows) suggested that the relative fishing power of the pots increased with the implementation of an escape window. This result could be explained as a “saturation effect”, i.e. the probability of cod entering the pot is likely to be negatively dependent on cod density in the pot. The high species selectivity and the low catch rate of undersized fish have consolidated the floating pots position as a highly benign fishing method and the foremost alternative gear for the future coastal cod fishery in the Baltic Sea. [ABSTRACT FROM AUTHOR]