Search

Based on length, weight, and age data, we examined allometry and growth parameters for common pandora, Pagellus erythrinus, commercially collected seasonally from northern and southern Tunisian coasts in 2007. A total of 370 specimens (14-27.5 cm in length) were used to assess the allometric variation at seasonal scales. The slope b values (regression coefficient) of the length-weight relationship varied between 2.494 to 3.237, indicating (roughly) an isometric to negative allometric growth pattern. The allometric relationship, as a proxy for fish condition, seems to be affected by seasons and sex in the northern population, while only seasons seem to have a strong effect in the southern population, as indicated by ANOVA. The von Bertalanffy growth parameters were identified at L∞ = 34.076 and 28.017 cm, k = 0.153 and 0.150/year, and t0 = -1.922 and -3.961 years for the northern and southern sample, respectively. [ABSTRACT FROM AUTHOR]

The demography and reproductive biology of three Epinephelus groupers (Serranidae), namely E. polyphekadion, E. tauvina, and E. howlandi in the Yaeyama Islands, Okinawa, were examined based on age assessment using otoliths and gonadal histology. The maximum ages for these three species were 26 year, 23 year, and 17 year. The von Bertalanffy growth functions were also determined for each species. The size and age at 50% female maturity were estimated to be 358 mm in total length (TL) and 6.0 year for E. polyphekadion, 371 mm TL and 6.7 year for E. tauvina, and 327 mm TL and 4.1 year for E. howlandi, respectively. Significant differences between the sexes in size and age frequencies were found in all three species, with males being larger and older than females, or transitional individuals. These results strongly indicated that the population of these three grouper species showed monandric protogynous hermaphroditism. The sex ratios of E. polyphekadion and E. tauvina were biased in favor of females, but that of E. howlandi was equivalent between sexes. The relative sizes of ripe testes indicated that the intensity of sperm competition varied among species suggesting different mating system of each species. Reproductive seasonality was similar among species, with active vitellogenesis coinciding with the annual rise in water temperature. The active spawning period was determined to be between April and May for E polyphekadion, in May for E. howlandi, and from March to June for E. tauvina. [ABSTRACT FROM AUTHOR]

With invasive lionfish (Pterois spp.) increasing throughout the western North Atlantic Ocean and Gulf of Mexico (GOM), it is important to define life history characteristics to help understand the invasion and potential effects on receiving ecosystems. Although some aspects of reproduction are known elsewhere in the invaded range, little is known in the northern GOM [nGOM; Florida Keys (24.66°N) to south Texas (26.00°N)]. In the present study, gonadosomatic index (GSI) calculations were based on 4527 red lionfish Pterois volitans (Linnaeus, 1758) specimens (April 2012-March 2015). Male and female GSI peaked from May to October, corresponding with macroscopic gonadal assessments of reproductively active females. Histological examination of ovaries from 355 females found they were spawning capable during all months. Males (n = 211) were spawning capable in all months except March, the only month in which no actively spawning females were present. A significantly higher percentage of reproductively active females was found from May to December. Lionfish reached 50% maturity at a small size (166.6 mm TL, females; 145.2 mm TL, males). Mean relative batch fecundity (n = 71) was 92 eggs g-1 gonad-free body weight (GFBW) and was highest in August (207 eggs g-1 GFBW). The population spawning frequency was estimated to be every 2.5 d over 11 mo in the nGOM, corresponding to a maximum potential annual output of 2,332,490 eggs for an average sized (188.6 g) female. These reproductive characteristics are similar to invasive lionfish in tropical waters, although nGOM reproductive output appears higher. Our results represent the most comprehensive reproductive data on lionfish in their invaded range, and provide a baseline for management in the nGOM. [ABSTRACT FROM AUTHOR]

The embryonic development of the Japanese eel Anguilla japonica and pike eel Muraenesox cinereus was morphologically investigated with laboratory-reared specimens to clarify the characteristics of somitogenesis. In A. japonica, somites were first observed at 18 h post fertilization (hpf) when epiboly reached 90%. Somitogenesis progressed at a rate of 1·6 h−1 at mean ± s.d. 22·6 ± 0·7° C and completed at 107 hpf (3 days post hatching; dph) when total number of somites ( ST) reached 114, which corresponds to the species' number of vertebrae (112-119). In M. cinereus, somites were first observed at 14 hpf when epiboly completed. Somitogenesis progressed at a rate of 1·9 h−1 at mean ± s.d. 24·4 ± 0·2° C and completed at 90 hpf (2 dph) with 149 ± 4 ST, which corresponds to the species' number of vertebrae (142-158). Both species hatched before somitogenesis was completed, at 37 hpf with 47 ST and 42 hpf with 82 ± 4 ST, respectively. The formation of other organs such as the heart, mouth and pectoral fin bud occurred during somitogenesis. Comparison with the development of zebrafish Danio rerio indicates a prolongation of somitogenesis in A. japonica and M. cinereus. Their somitogenesis rates, however, correspond well with that of D. rerio estimated at the same temperature and their developmental stages at hatching are almost equivalent to other fishes having similar yolk sizes. Therefore, the prolongation of somitogenesis in A. japonica and M. cinereus may be accounted for solely by the increased numbers of somites to be formed, not by a slow somitogenesis rate or an acceleration in organogenesis. [ABSTRACT FROM AUTHOR]

Biological characteristics of Pentaceropsis recurvirostris, Paristiopterus gallipavo and Parazanclistius hutchinsi were determined from commercial gillnet samples from temperate south-western Australian coastal waters. Growth zones in otoliths, with more than a few such zones, were readily detectable only after the otoliths had been sectioned. Visual analyses and modelling of the trends in marginal increments on sectioned otoliths demonstrate that these opaque zones are formed annually. Maximum ages of 55, 36 and 49 years, derived for P. recurvirostris, P. gallipavo and P. hutchinsi, respectively, reflect relatively low mortalities. These longevities greatly exceed those estimated, using otoliths, for Pentaceros wheeleri and Pentaceros richardsoni, which belong to the other pentacerotid subfamily. These differences may be due to the counts of 'daily' growth zones in sectioned otoliths of P. wheeleri not representing the complete age range of that species and the zones detected in whole otoliths of P. richardsoni not constituting the complete range of annually-formed zones. Pentaceropsis recurvirostris, P. gallipavo and P. hutchinsi recruited into the fishery in the sampling area as 2-3 year-old fishes. Pentaceropsis recurvirostris and P. hutchinsi exhibited little or no subsequent growth throughout the remainder of their protracted life, whereas, P. gallipavo continued to grow for c. 5 years and then underwent little further growth. Spawning of P. recurvirostris and P. hutchinsi peaked in the austral winter and autumn, respectively, but in the austral spring and summer with P. gallipavo, which is more typical of temperate species. Although the females of P. gallipavo and P. hutchinsi were mature, this did not apply to a few P. recurvirostris, some of which were >20 years old, implying that any given female of this species does not always spawn every year. Ovarian mass greatly exceeded testis mass, indicative of pair spawning, which is consistent with field observations. In contrast to P. recurvirostris and P. hutchinsi, the sex ratio was heavily biased towards males and the spawning period longer in P. gallipavo, suggesting that selection pressures for spawning success were greater for this latter species. [ABSTRACT FROM AUTHOR]

A survey of kidney bacteria from female landlocked fall Chinook SalmonOncorhynchus tshawytschabroodstock from Lake Oahe, South Dakota, was conducted to investigate possible links to subsequent egg survival. Bacteria were isolated from 22 spent females. The kidneys of two females contained no bacteria, and no eggs survived from the spawn of these two fish. All kidneys sampled appeared normal with no gross abnormalities. Twelve bacteria genera were isolated and identified to the genus level:Acinetobacter, Aeromonas, Brevundimonas, Chryseobacterium, Flavobacterium, Acidovorax, Arthrobacter, Deinococcus, Enterococcus, Leucobacter, Micrococcus,andOerskovia. Screening forRenibacterium salmoninarumwas not conducted. Colony forming units (CFU) per gram ranged from 0 to 10,542. There were no significant correlations between egg survival and CFU from samples incubated on agar containing either R2A or Coomassie Brilliant Blue. In addition, no relationship was observed between any of the bacterial species isolated and egg survival to the eyed stage. Bacteria present in the kidneys of this specific population of Chinook Salmon do not appear to have any effect on female condition or subsequent egg survival, although several potentially pathogenic bacteria genera were isolated. Received July 1, 2015; accepted September 6, 2015 [ABSTRACT FROM PUBLISHER]

Female Channel Catfish Ictalurus punctatus × male Blue Catfish I. furcatus hybrids are normally harvested by seining single‐batch pond or split‐pond production systems in fall or winter. Ponds are typically restocked with fingerlings without draining. There is concern that without completely draining the pond after harvest, food‐size hybrids that escape seining may cannibalize restocked fingerlings. The purpose of this study was to determine if such hybrid fingerlings stocked after the fall harvest would be cannibalized by the larger carryover fish during winter or the following growing season. Three 0.04‐ha ponds were each stocked on November 25, 2013, with 100 food‐size hybrid catfish averaging 1.07 kg. Those three ponds and an additional three ponds were then stocked on November 27, 2013, with 300 hybrid catfish fingerlings averaging 14.8 g. The fish were not fed over winter. Mean survival of the fingerlings after 4 months at 91.9% and 92.9% was not significantly different between treatments. Survival of the food‐size fish was 99.7%. Four ponds stocked with fingerling and food‐size hybrids and an additional four ponds stocked with just fingerlings in April 2014 were harvested in October. Survival of the fingerlings was not significantly different between ponds with (88.8%) and without (90.3%) food‐size fish. We found no significant intercohort cannibalism by food‐size hybrid catfish on understocked fingerlings either overwinter or during the following growing season. [ABSTRACT FROM AUTHOR]

Subyearling (age‐0) hatchery summer‐run Chinook Salmon Oncorhynchus tshawytscha have been released into the Columbia River in mid‐June from Wells Fish Hatchery, Washington, since 1993, but release‐to‐adult survival (SAR) under this strategy has been low. I used paired releases of four broods of coded‐wire‐tagged age‐0 Chinook Salmon released in mid‐May (early release [ER] group) and mid‐June (late release [LR] group) to evaluate whether advancing the release date could improve SAR. Additionally, passive integrated transponder tags implanted in a subsample of each release group were used to estimate emigration rate and release‐to‐McNary Dam survival of juvenile fish. Mean migration rate from release to McNary Dam was significantly faster for LR fish than for ER fish. No among‐year difference in mean survival from release to McNary Dam was observed between ER and LR groups, although differences were observed within years. Mean overall SAR was significantly greater for ER fish than for LR fish. These results suggest that altering the release date of age‐0 Chinook Salmon at Wells Hatchery would enhance return survival. [ABSTRACT FROM AUTHOR]

Survival estimates were obtained for the Norway lobster, Nephrops norvegicus , retained and escaping from a standard 70 mm mesh size diamond and a modified 55 mm square mesh codend, on board a commercial vessel in fishing grounds off the Portuguese south coast. Ten hauls were carried out, five with each experimental codend, plus three creel sets for the capture of a control group in an adjacent non-trawled area. A total of 571 lobsters were sampled upon arrival on vessel deck, either captured in the codend or retained in the codend cover. In addition, a total of 25 individuals were caught with creels. They were assessed for physical damage and vitality and subsequently placed in cages which were deployed in the same adjacent area for 48 h. Average survival rates were 0.18 and 0.17 for retained individuals and 0.17 and 0.30, for individuals escaping through diamond and square meshes, respectively, and 0.84 for creeled individuals. A discussion is carried out stressing the difficulty in disentangling the influence of the different factors contributing to condition and mortality of individual lobsters. [ABSTRACT FROM AUTHOR]

Increased fishing pressure on deep-water demersal fishes in relatively recent times highlights the need for a better understanding of their biology, demography and relative abundance. The eightbar grouper Hyporthodus octofasciatus is one of the largest species of Epinephelidae and is highly valued in relatively deep-water fisheries throughout the Indo-West Pacific region. Currently, information on the life history of H. octofasciatus is limited to the south-eastern Indian Ocean. We compared estimated life history parameters for H. octofasciatus from this region with the western central Pacific Ocean. Histological examination of gonads of H. octofasciatus from a wide length and age range (295–1740 mm TL and 6–65 years) suggested that this species is a protogynous hermaphrodite in the Pacific Ocean, which is consistent with data for this species in the south-eastern Indian Ocean and its congeners. However, the maximum length (1740 mm TL), asymptotic length ( L ∞ , 1912 mm TL) and longevity (65 years) were much greater in the Pacific compared to the Indian Ocean (1509 mm TL, 1166 mm TL and 47–56 years), resulting in substantially different growth trajectories and a lower instantaneous rate of natural mortality in the Pacific Ocean (i.e., 0.06 vs 0.09 year −1 ). Such regional variations in life history traits across the Indo-Pacific need to be considered in assessments and management of H. octofasciatus stocks within and across jurisdictions. [ABSTRACT FROM AUTHOR]

Bomb radiocarbon dating was used to determine the periodicity of band pair formation in the vertebral centra of three common thresher sharks ( Alopias vulpinus). The traditional interpretation of band pairs were accurate (i.e. annual) up to approximately 14 years of age. In older individuals, band pair counts underestimated age. A new maximum validated age was estimated to be 38 years (an increase of 18 years over the band count estimates). Previously reported length at age estimates for common thresher sharks up to 14 years were used in conjunction with the two older validated estimates to develop a revised growth curve for the species, which was described using the Schnute general model (sexes combined). Updated estimates of age at maturity remained the same for males (8 years) and increased by one year to 13 years for females. The primary finding was the increase in longevity for this species from a band pair count estimate of 24 years to a bomb radiocarbon validated estimate of 38 years, indicating this species lives much longer than previously thought. [ABSTRACT FROM AUTHOR]

Predictive models have been used to determine fish species that occur less frequently than expected (decreasers) and those that occur more frequently than expected (increasers) in streams in the eastern U.S. Coupling life history traits with 51 decreaser and 38 increaser fish species provided the opportunity to examine potential mechanisms associated with predicted changes in fish species distributions in eastern streams. We assigned six life history traits - fecundity, longevity, maturation age, maximum total length, parental care, and spawning season duration - to each fish species. Decreaser species were significantly smaller in size and shorter-lived with reduced fecundity and shorter spawning seasons compared to increaser species. Cluster analysis of traits revealed correspondence with a life history model defining equilibrium (low fecundity, high parental care), opportunistic (early maturation, low parental care), and periodic (late maturation, high fecundity, low parental care) end-point strategies. Nearly 50 % of decreaser species were associated with an intermediate opportunistic-periodic strategy, suggesting that abiotic factors such as habitat specialization and streamflow alteration may serve as important influences on life history traits and strategies of decreaser species. In contrast, the percent of increaser species among life history strategy groups ranged from 21 to 32 %, suggesting that life history strategies of increaser species were more diverse than those of decreaser species. This study highlights the utility of linking life history theory to biodiversity to better understand mechanisms that contribute to fish species distributions in the eastern U.S. [ABSTRACT FROM AUTHOR]

Variation in age and size of mature nine-spined sticklebacks (Pungitius pungitius) within and among 16 Fennoscandian populations were assessed using skeletochronology. The average age of individuals in a given population varied from 1.7 to 4.7 years. Fish from pond populations were on average older than those from lake and marine populations, and females tended to be older than males. Reproduction in marine and lake populations commenced typically at an age of two years, whereas that in ponds at an age of three years. The maximum life span of the fish varied from 3 to 7 years. Mean body size within and among populations increased with increasing age, but the habitat and population differences in body size persisted even after accounting for variation in population age (and sex) structure. Hence, the population differences in mean body size are not explainable by age differences alone. As such, much of the pronounced intraspecific variation in population age structure can be attributed to delayed maturation and extended longevity of the pond fish. The results are contrasted and discussed in the context of similar data from the three-spined stickleback (Gasterosteus aculeatus) occupying the same geographic area. [ABSTRACT FROM AUTHOR]

Variation in age and size of mature nine-spined sticklebacks (Pungitius pungitius) within and among 16 Fennoscandian populations were assessed using skeletochronology. The average age of individuals in a given population varied from 1.7 to 4.7 years. Fish from pond populations were on average older than those from lake and marine populations, and females tended to be older than males. Reproduction in marine and lake populations commenced typically at an age of two years, whereas that in ponds at an age of three years. The maximum life span of the fish varied from 3 to 7 years. Mean body size within and among populations increased with increasing age, but the habitat and population differences in body size persisted even after accounting for variation in population age (and sex) structure. Hence, the population differences in mean body size are not explainable by age differences alone. As such, much of the pronounced intraspecific variation in population age structure can be attributed to delayed maturation and extended longevity of the pond fish. The results are contrasted and discussed in the context of similar data from the three-spined stickleback (Gasterosteus aculeatus) occupying the same geographic area. [ABSTRACT FROM AUTHOR]

Samples of Shortnose Mojarra Diapterus brevirostris were obtained from the commercial catch from April 2010 to July 2012, morphometric data of 394 individuals were registered. The growth study entailed two methods: length frequency analysis and study of sagittae and asterisci otoliths. Both methods identified six age groups. Growth parameters of von Bertalanffy's equation were determined by Ford-Walford and Gulland methods and by ELEFAN routine adjustment. Both methods gave the same results: L∞= 48.61 cm, K= 0.135, to= -0.696. Mean size for each age was: age 1= 9.97 cm, age 2= 14.86 cm, age 3= 19.13 cm, age 4= 22.87 cm, age 5= 26.12 cm and age 6= 28.97 cm. The allometric index from the weight-length relationship was isometric and b= 2.977, the longevity was of 21.5 years. The growth ring is marked because of the metabolic changes in the fish together with its response to environmental factors. The use of the growth parameters obtained by different methods is a robust result in the use of fishery models. [ABSTRACT FROM AUTHOR]

Growth characteristics are poorly understood for speckled hind ( Epinephelus drummondhayi), a tropical deep-water grouper of economic importance that is considered overfished. Age has been validated for early growth, but the validity of adult age estimates is unknown. A few studies of growth zones in otoliths have revealed maximum age estimates of 15-35 years, which have been uncritically assumed as longevity. To answer questions about adult age, bomb radiocarbon dating was used to provide validated age estimates. A novel aspect of this study was use of the postbomb radiocarbon decline period (ca. 1980-2004) to age younger fish, an approach that was validated with known-age otoliths. Bomb radiocarbon dating provided valid length-at-age estimates ranging from ∼5 years to more than 45 years. Age was unexpectedly greater than previous estimates for more than half the fish used in this study, and longevity may approach 60-80 years. This study extends the utility of bomb radiocarbon dating by more than 20 years and adds to the growing perspective that deep-water tropical fishes can be long-lived. [ABSTRACT FROM AUTHOR]

Barnard's dentex Dentex barnardi is a relatively slow-growing, late-maturing species with an intermediate longevity (maximum recorded age = 13 years). The length and age structures of the population were similar for males and females; however, the sex ratio was female biased at 1:1.6. Growth was described by the three-parameter von Bertalanffy model as Lt = 332.14(1 - e–0.14(t + 3.97)). The species is a rudimentary hermaphrodite and the length- and age-at-50% maturity was calculated as 220 mm fork length and 3.7 years respectively. Reproductive activity in fish sampled in southern Angola was observed over an extended period during the austral summer (August–February) and a drop in water temperature is a possible ultimate cue for spawning activity in this species. The diet consisted mainly of teleost fish and mysid shrimps. The life-history characteristics of the species render it susceptible even to low levels of fishing pressure. Owing to the paucity of information on the fisheries for D. barnardi, and the current fisheries management situation in Angola, conventional management tools are not considered appropriate. The establishment of marine protected areas is suggested as the most appropriate management strategy for the species. [ABSTRACT FROM AUTHOR]

The purpose of this study was to assess the validity of age estimates for the striped shiner Luxilus chrysocephalus and the duskystripe shiner Luxilus pilsbryi using asterisci otoliths, scales, and length data. Both species were sampled monthly from the headwater reaches of the James River in southwestern Missouri from February 1998 to January 1999. The formation of an annual opaque region was validated using edge analysis, whereby the progression of annulus formation is followed throughout the year. A single opaque region was formed in otoliths, primarily during May in striped shiners and June and July in duskystripe shiners. Agreement between otolith and scale ages was over 95% for fish 0–3 years old. However, scales commonly underestimated age for fish of ages greater than 3. For both species, the ages of individuals based on otoliths ranged from 0 to 6 years. Population age structure indicated higher rates of survival and longevity for females and faster growth rates for males of both species. The most notable life history differences between species were the accelerated growth rate of adult male striped shiners and the uniform age structure for female duskystripe shiners. Received December 1, 2010; accepted December 15, 2011 [ABSTRACT FROM AUTHOR]

Abstract: It is generally perceived that all deep-sea fishes have great longevity, slow growth, and low reproductive output in comparison to shelf dwelling species. However, such a dichotomy is too simplistic because some fishes living on continental slopes are relatively fecund and fast growing, important considerations in respect to the management of expanding deep-sea fisheries. We tested two hypotheses that might explain variation in life history attributes of commercially exploited demersal fishes: (1) phylogeny best explains the differences because deep-sea species are often in different families from shelf dwelling ones and, alternatively, (2) environmental factors affecting individual life history attributes that change with depth account for the observed variation. Our analysis was based on 40 species from 9 orders, including all major commercially exploited deep-sea fishes and several phylogenetically related shelf species. Depth of occurrence correlated significantly with age at 50% maturity increasing linearly with depth (r 2=0.46), while the von Bertalanffy growth coefficient, maximum fecundity and potential rate of population increase declined significantly and exponentially with depth (r 2=0.41, 0.25 and 0.53, respectively). These trends were still significant when phylogenetically independent contrasts were applied. The trends were also consistent with similar slopes amongst members of the order Gadiformes and the order Scorpaeniformes. Reduced temperatures, predation pressure, food availability, or metabolic rates may all contribute to such changes with depth. Regardless of the mechanisms, by analyzing a suite of fishes from the shelves to the slope the present analysis has shown that rather than a simple dichotomy between deep-sea fishes and shelf fishes there is a continuum of life history attributes in fishes which correlate strongly with depth of occurrence. [Copyright &y& Elsevier]

The life histories of two globally endangered hammerhead sharks, Sphyrna lewini and Sphyrna mokarran, were examined using samples collected from a range of commercial fisheries operating along the east coast of Australia. The catch of S. lewini was heavily biased towards males, and there were significant differences in von Bertalanffy growth parameters ( L and k) and maturity [stretched total length ( L) and age ( A) at which 50% are mature, L and A] between those caught in the tropics ( L = 2119 mm, k = 0·163, L = 1471 mm, A = 5·7 years) and those caught in temperate waters ( L = 3199 mm, k = 0·093, L = 2043 mm, A = 8·9 years). The best-fit estimates for a three-parameter von Bertalanffy growth curve fit to both sexes were L = 3312 mm, L = 584 mm and k = 0·076. Males attained a maximum age of 21 years and grew to at least 2898 mm L. The longevity, maximum length and maturity of females could not be estimated as mature animals could not be sourced from any fishery. Length at birth inferred from neonates with open umbilical scars was 465-563 mm L. There was no significant difference in length and age at maturity of male and female S. mokarran, which reached 50% maturity at 2279 mm L and 8·3 years. Sphyrna mokarran grew at a similar rate to S. lewini and the best-fit estimates for a two-parameter von Bertalanffy equation fit to length-at-age data for sexes combined with an assumed mean length-at-birth of 700 mm were L = 4027 mm and k = 0·079. Females attained a maximum age of 39·1 years and grew to at least 4391 mm L. The oldest male S. mokarran was 31·7 years old and 3691 mm L. Validation of annual growth-band deposition in S. mokarran was achieved through a mark, tag and recapture study. [ABSTRACT FROM AUTHOR]

Abstract: The east Atlantic-Mediterranean penaeid Melicertus kerathurus constitutes a valuable resource for Mediterranean fisheries. In recent years, its world production is almost totally based on the yields from Greece and Tunisia. A two-year study of prawn stock in Thermaikos Gulf (NW Aegean Sea) provided information on age, growth and mortality of the species. M. kerathurus exhibits a marked sexual growth dimorphism, with females showing an overall wider size range and greater size than males. Mean monthly size, CLmax were also in favor of females. Monthly age classes varied from one to four for females and from one to three for males, and corresponded to three generations (0+, 1+, 2+). New generation (0+) cohorts recruited into fishery in waves, from late summer to February. According to the von Bertalanffy growth curve, females grow larger than males, but there is a prominent seasonal growth oscillation in both sexes (females: CL∞ =62.48, K =1.15, C =0.87, WP=0.16, Rn=0.170; males: CL∞ =47.78, K =1.28, C =0.97, WP=0.12, Rn=0.205). Growth performance indices (φ′, φ) and longevity were in favor of females. K values for both sexes in Thermaikos Gulf are the highest reported for the species, suggesting a higher growth rate and a lower longevity. Estimated values for total, natural and fishery mortality were greater in males. In both sexes, an exploitation rate E >0.5 was found, implying an intense fishing impact on M. kerathurus stock in Thermaikos Gulf. Intense exploitation in other parts of the Mediterranean and eastern Atlantic, along with the replacement of the species by Eritrean penaeid prawns in the eastern Mediterranean, has resulted in a severe reduction in catches, in most countries. Thus, existing stocks of M. kerathurus should be considered as potentially endangered, and species-specific initiatives towards sustainable management of this resource should be implemented. [Copyright &y& Elsevier]

Concentrations of 24 trace metals were assessed in gravid ovaries and in muscle of female juvenile and adult female goldeye (Hiodon alosoides), a fish with both low annual growth (16 g/year as adults) and a long life span (maximum longevity of 30 years). It was hypothesized that adult fish with these life-history characteristics would maintain stable concentrations of metals in their tissues with higher levels of essential elements compared with those that are potentially toxic. As hypothesized, the concentration of most metals in muscle of adult female goldeye was similar at all ages, suggesting that uptake and excretion of metals was equal. Mercury was a notable exception. Total Hg concentrations in muscle of adults increased throughout life from a mean of 206 ng/g wet weight at age 8 to 809 ng/g at age 28, or by 26.2 ng/g/year. Concentrations of Hg were low in ovaries (mean 21.1 ng/g wet wt) compared to the mean for muscle, only 7% of the concentration in muscle. This was the lowest percent of muscle concentration of all 24 metals. Concentrations of Al, Ba, La, V, and Mn were significantly greater in muscle of juveniles and in ovaries than in muscle of adults. Concentrations of 13 metals were higher in ovaries relative to muscle, seven were similar, and four were depleted. Silver was enriched by over 50-fold in ovaries. Overall, the present study suggests that low concentrations of some metals in muscle of adult female goldeye, relative to concentrations in female juveniles and ovaries, may be maintained in part by transfer of metals to the external environment in eggs at spawning. Environ. Toxicol. Chem. 2010;29:373–379. © 2009 SETAC [ABSTRACT FROM AUTHOR]

A rudimentary understanding of age, growth, and life-span is lacking for many non-game fishes. Growth characteristics of the central mudminnow ( Umbra limi) have not yet been accurately described using reliable hard part analysis. The utility of scales and otoliths as ageing structures and quantified growth was examined in one lake and one stream population of central mudminnow. Scales were found to be of no utility in determining age due to inconsistent formation of yearly annuli and a high incidence of regenerated scales, while otoliths were easily extracted and considered to be an accurate ageing structure. Ages determined from scales were low compared to those from otoliths, and the difference in age interpreted from the two structures increased with fish age. A power function was fitted to describe the length-weight relationship for this species ( a = 0.0069, b = 3.175). Von Bertalanffy growth parameters were estimated and compared for each population (Lake: L∞ = 114.20 mm, K = 0.30, t0 = −0.93; Stream: L∞ = 77.59 mm, K = 0.63, t0 = −0.76). The lake population showed greater size at age compared to the stream population, especially at older ages, and achieved a larger maximum size. Growth rate was also greater in the lake population (Lake: 1.74; Stream: 1.09 g year−1). Females were larger at age than males in both populations, however all individuals greater than age 3 were males. This work represents the first successful account of central mudminnow growth using hard part analysis. [ABSTRACT FROM AUTHOR]

The cod, Gadus morhua, is a common and abundant demersal fish in the White Sea coastal zone. The published data on the maximum age of White Sea cod still requires additional documentation, because some authors have noted difficulties in age determination by otoliths of large specimens. To obtain accurate data on the longevity of this species in the White Sea, an image analysis of thin-sections of otoliths was made for age estimation. Research surveys in the Chupa Inlet and adjacent waters of the Kandalaksha Bay were conducted in June to August from 2007 to 2013. The five largest specimens of a total of 3564 captured fish were selected for age determination. Age of these largest individuals ranged between 7 and 12 years, total length and weight varied from 60.2 to 77.0 cm and from 2.4 to 6.1 kg, respectively. According to the data, maximal White Sea cod longevity is greater than in previously published data, and demonstrates similar longevity to conspecifics from the Baltic and North seas, whereas its life cycle is much shorter than cod from the Northeast Arctic, Iceland, Greenland, Newfoundland and Labrador stocks. [ABSTRACT FROM AUTHOR]

Abstract: Compared to total mercury concentrations in other oceanic pelagic and syntopic fish species examined from waters of the southeastern United States (e.g., king mackerel, Scomberomorus cavalla; wahoo, Acanthocybium solanderi; yellowfin tuna, Thunnus albacares; blackfin tuna, T. atlanticus), total mercury concentrations in dolphinfish, Coryphaena hippurus, examined were consistently low. Dorsal-muscle tissue from 385 dolphinfish (317–1395mm fork length) from Florida offshore waters was analyzed for total mercury content. Total mercury concentration in individual fish ranged from 0.012 to 0.55mg/kg (wet weight), with a mean of 0.10mg/kg (±0.089SD). Compared to mercury concentrations in other similar species, mercury concentrations detected in dolphinfish did not vary widely with respect to fish size, estimated age, or sex. A positive relationship between total mercury concentrations and fish length was observed, indicating that mercury tends to increase moderately over time as dolphinfish grow. Low mercury concentrations in dolphinfish occur on a global scale throughout tropical and subtropical waters. The short life span, rapid growth rate, known physiology, and feeding ecology of dolphinfish are comparable regardless of where they are found, suggesting that the forcing factors that influence mercury concentrations in this species are similar throughout its circumtropical range. [Copyright &y& Elsevier]

The short-lived annual fish Nothobranchius furzeri shows extremely short captive life span and accelerated expression of age markers, making it an interesting model system to investigate the effects of experimental manipulations on longevity and age-related pathologies. Here, we tested the effects of dietary restriction (DR) on mortality and age-related markers in N. furzeri. DR was induced by every other day feeding and the treatment was performed both in an inbred laboratory line and a longer-lived wild-derived line. In the inbred laboratory line, DR reduced age-related risk and prolonged maximum life span. In the wild-derived line, DR induced early mortality, did not reduce general age-related risk and caused a small but significant extension of maximum life span. Analysis of age-dependent mortality revealed that DR reduced demographic rate of aging, but increased baseline mortality in the wild-derived strain. In both inbred- and wild-derived lines, DR prevented the expression of the age markers lipofuscin in the liver and Fluoro-Jade B (neurodegeneration) in the brain. DR also improved performance in a learning test based on conditioning (active avoidance in a shuttle box). Finally, DR induced a paradoxical up-regulation of glial fibrillary acidic protein in the brain. [ABSTRACT FROM AUTHOR]

Background: The main prediction of life-history theory is that optimal energy allocated among the traits is related to the growth, maintenance and survival. It is hypothesized that the optimal resource allocated to immune function, which generates resistance towards parasites and reduce the fitness losses caused by parasitism, is depending on other requirements for energetic resource and the benefits associated with them. The aims of this study are to investigate in a comparative way (1) how parasitism is related to fish life history traits (fecundity, longevity, mortality), (2) whether there is a trade-off between reproduction and immune investments in fish females (i.e. energetic hypothesis) and in males (i.e. immunohandicap hypothesis), (3) whether parasitism influences host immunity (spleen size) and reproduction (gonad size) in females and males. Results: Data on metazoan parasites of 23 cyprinid fish species from Central Europe were used for the analyses as well as new data collected from a field study. Ectoparasite species richness was negatively correlated with the fish mortality estimated by the k-value and positively correlated with fish body size, suggesting that parasite diversity increases with fish longevity. A negative relationship between spleen size and gonad size, controlling for fish body size, was found in females but not in males. Moreover, parasite abundance was positively correlated with fish spleen size and negatively with fish gonad size in females. Conclusion: The comparative analyses using cyprinid fish species demonstrated that natural mortality could be considered as a factor contributing to the variability of parasite species richness and moreover, parasite species benefit from long-lived fish. The results obtained from the analyses investigating the potential trade-off between reproduction and immunity could be interpreted as an energetic trade-off between female reproduction and immune function. The lack of negative relationship between gonad size and spleen size in males did not support our prediction based on the immunohandicap hypothesis. [ABSTRACT FROM AUTHOR]

This Hot Topics review, the first in a projected annual series, discusses those articles, published in the last year, which seem likely to have a major impact on our understanding of the aging process in mammals and the links between aging and late-life illnesses. The year's highlights include studies of oxidation damage in the very-long-lived naked mole-rat, and of caloric restriction in monkeys, humans, and growth hormone-unresponsive mice. Two studies of resveratrol, one showing its ability to extend lifespan in a short-lived fish, the other demonstrating beneficial effects in mice subjected to a diet high in fat, may well be harbingers of a parade of intervention studies in the coming decade. [ABSTRACT FROM AUTHOR]

Describes two approaches for predicting mortality rate based solely on the longevity of the members of a fish stock. Development of and challenge in the rule-of-thumb approach; Difference in the estimates of mortality generated by the approaches; Comparison of the linear regression model with the rule-of-thumb approach.

Atmospheric testing of thermonuclear devices during the 1950s and 1960s created a global radiocarbon (14C) signal that has provided a useful tracer and chronological marker in oceanic systems and organisms. The bomb-generated 14C signal retained in fish otoliths can be used as a time-specific recorder of the 14C present in ambient seawater, making it a useful tool in age validation of fishes. The goal of this study was to determine 14C in otoliths of the age-validated yelloweye rockfish (Sebastes ruberrimus) to establish a reference time series for the coastal waters of southeast Alaska. Radiocarbon values from the first year's growth of 43 yelloweye rockfish otoliths plotted against estimated birth year produced a 14C time series (1940–1990) for these waters. The initial rise of 14C occurred in 1958 and 14C levels rose to peak values (60–70‰) between 1966 and 1971, with a subsequent declining trend through the end of the record in 1990 (–3.2‰). In addition, the 14C data confirmed the longevity of the yelloweye rockfish to a minimum of 44 years and strongly support higher age estimates. This 14C time series will be useful for the interpretation of 14C accreted in biological samples from these waters. [ABSTRACT FROM AUTHOR]

Exploited deepwater (>500 m) species generally exhibit clear “K-selected” life-history characteristics markedly different from most shelf species: extreme longevity, late age of maturity, slow growth, and low fecundity. Many also aggregate on restricted topographic features such as seamounts, and as a consequence are notably unproductive, highly vulnerable to overfishing, and have potentially little resilience to overexploitation. Since 1964, deepwater fisheries have contributed 800 000–1 000 000 t annually to global marine fish landings. Underlying this apparent overall stability is the “boom and bust” cycle that has characterized many individual fisheries. The accumulated biomass of previously unfished stocks is typically fished down, often within 5–10 years, to the point of commercial extinction or very low levels. Most deepwater stocks are today overfished or even depleted. Depletion of species from deep-sea environments that dominate mid to upper trophic levels may have long-term ecological implications, but the risks of reduced stock size and age structure to population viability, the potential for species replacement, and the impacts on prey and predator populations are not generally known. However, trawl fisheries have been shown to have potentially severe impacts on the benthic fauna of seamounts, where these fish aggregate. This fauna, dominated by suspension feeders, such as corals, is typically restricted to the seamount environment and is characterized by high levels of endemism, which suggests limited reproductive dispersal. The ability of the benthic community to recover, following its removal by trawling, is not known. [ABSTRACT FROM PUBLISHER]

Early life history traits of fish are very variable as a result of both genetic and environmental factors. In this study, we examine individual variation in early life history traits in progeny of seven females crossed with one male rainbow trout, Oncorhynchus mykiss (Walbaum). Individual eggs were followed from fertilization through hatching until death of the larvae by starvation. Larvae and yolksac size (size was shown to be a good indicator of energy content) increased with increasing egg size, but there were still differences between families after variation in egg size was accounted for. Incubation time was not correlated with egg size, and did not differ between families. The progeny from the different families utilized the available energy differently, as both longevity and growth-rate without food was independent of yolk-sac size, but strongly dependent on family. The observed between-family differences in early life history traits in rainbow trout were mainly caused by genetically based effects; egg size and thus probably egg quality, which differed strongly bet ween females, could not adequately explain these differences. [ABSTRACT FROM AUTHOR]

Abstract: The age at first maturity and species longevity are two important life history parameters for both fishery and conservation management. A relationship between species longevity and the age at maturity was derived by combining previously developed methods by Rikhter and Efanov and Hoenig. Furthermore, indications are also given that the presented method might be in a better accordance with the life history of long-lived fish species than previous methods. Previous estimations of the relationship between the age at maturity and longevity of fish species have been characterized by linear functions. However, in species with the extreme longevity, the relationship between the age at maturity and longevity is not characterized by a linear function, and it tends to increase with age. The presented method can be used routinely as a tool to assess longevity and the age at maturity of a species when the data are scarce, and to improve our understanding and management of species, until better knowledge becomes available. [Copyright &y& Elsevier]