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Maternal influences on age-0 walleye (Sander vitreus (Mitchill, 1818)) recruit abundance and survival from egg to fall were observed in Escanaba Lake, Wisconsin, in 1957–2015. Annual egg production best explained variation in age-0 recruitment, compared with female relative abundance, and adult abundance (sexes combined). Age-0 recruitment was not significantly correlated with any temperature metric tested or our index of yellow perch (Perca flavescens (Mitchill, 1814)) abundance. Survival of walleye from egg to fall age-0 was positively correlated with the percent contribution of large females (>55.9 cm) to annual egg production. Mean size diversity of females by length class did not influence age-0 recruit abundance or survival over time. Evidence for maternal effects via size- and age-specific influences on fecundity and age-0 walleye survival suggest that exploitation may influence natural recruitment by altering adult female size structure. Given recent declines observed in walleye natural recruitment in the upper Midwestern USA, understanding the roles of maternal drivers and exploitation on recruitment is critical for sustainable walleye management. [ABSTRACT FROM AUTHOR]

Hatcheries can support salmon fisheries but also impact natural populations. We model the proportional hatchery contributions to ocean catch, natural-area spawning, and egg production based on hatchery production, maturation, fecundity, and straying. We develop indices of hatchery-origin catch per stray spawner measuring the trade-off between supplementing harvest and limiting natural-area impacts; higher values indicate success in increasing hatchery ocean harvest contributions relative to strays spawning in natural areas. Hatchery fish maturing early lowers catch per stray (and proportion hatchery-origin catch) by shifting the age distributions of both catch and spawners toward younger ages. Age-dependent fecundity may complicate predicted effects of changing maturation schedules. Increased straying does not affect catch but increases hatchery-origin spawning and decreases catch per stray. Differences in hatchery production affect hatchery contributions to both catch and spawning, exacerbating the trade-off between these conflicting goals but with no net effect on catch per stray. Fishery intensity magnifies the effects of accelerated hatchery fish maturation by reducing spawning contributions of older fish, with contrasting effects depending on whether hatchery fish mature early versus late. [ABSTRACT FROM AUTHOR]

A recent meta-analysis by Barneche et al. (2018; Science, 360(6389): 642–645) shows that fish reproductive output scales hypergeometrically with female weight. This result challenges the common assumption that reproductive output is proportional to weight. The implication made is that current theory and practice severely underestimate the importance of larger females for population replenishment. Their example for cod (Gadus morhua) shows that current practice makes an error of 149%. By properly accounting for fish demography, we show that the error is maximally on the order of 10% and in most other fish stocks likely much less. [ABSTRACT FROM AUTHOR]

Development of refined indices of female reproductive potential is needed for estimation of alternative biological reference points for the eastern Bering Sea (EBS) snow crab ( Chionoecetes opilio) fishery, which is managed with large male-only harvest regulations. Females were collected from 2007 to 2009 to investigate seasonal and interannual variation in fecundity with maternal size, shell condition (a proxy for age after maturity), and recent mating and again in 2010 to examine biochemical measures (carbon, hydrogen, and nitrogen) of embryo quality. Mean model-adjusted fecundity was highest for primiparous and young multiparous females and declined with advancing shell condition, presumably from senescence. This pattern was also found for clutch fullness indices evaluated from 20 years of stock assessment survey data. Indicators of low female sperm reserves were associated with decreased (∼10%) fecundity for multiparous females. Seasonal comparison of size-fecundity relationships suggested that embryo loss during brooding was minimal, and embryo quality analyses suggested that strong variation with maternal characteristics was unlikely. Finally, fecundity-at-size of EBS females may be lower than that of conspecifics in Japan and eastern Canada. [ABSTRACT FROM AUTHOR]

In a stable population, the adult lifetime reproductive value must be balanced against early life survival. Although delaying maturity may increase fecundity, it also reduces survival. Larger size at maturity therefore not only allows for higher fecundity, but requires it. Using simple arguments from life history, we derive a direct proportionality relationship between the adult lifetime reproductive value and weight at maturation and find that this relationship is consistent with empirical evidence from 28 stocks and species of bony fish from temperate-boreal environments. However, the expected proportionality falls off if mortality increases to include fishing. Furthermore, we find that the fecundity type (determinate or indeterminate) affects the predicted adult reproductive value, which is significantly (10-fold) higher for an indeterminate spawner than for a determinate spawner of the same weight. These differences may relate to trade-offs in the adult life history traits and (or) to seasonality in the spawning environment, with subsequent consequences for early life stage survivorship. [ABSTRACT FROM AUTHOR]

Animals partition and trade off their resources between competing needs such as growth, maintenance, and reproduction. Over a lifetime, allocation strategies should result in distinct trajectories for growth, survival, and reproduction, but such longitudinal individual data are difficult to reconstruct for wild animals and especially marine fish. We were able to reconstruct two of these trajectories in wild-caught Northeast Arctic cod ( Gadus morhua) females: size-at-age was back-calculated from otolith growth increments, and recent spawning history was reconstructed from postovulatory follicles and present oocyte development. Our findings indicate distinct trade-offs between length growth and reproduction. Fish that sexually matured early had attained a larger size at age 3 than immatures, but onset of reproduction caused slower growth compared with immatures. We found that 6- and 7-year-old females skipping spawning grew significantly more in the year of missed spawning than females spawning for the second consecutive year. The latter tentatively supports the hypothesis that skipped spawning may occur as an adaptive life-history strategy, given the potential future fecundity gain with increased size. [ABSTRACT FROM AUTHOR]

Hybridization with rainbow trout is a primary threat to the conservation of westslope cutthroat trout ( Oncorhynchus clarkii lewisi; hereafter cutthroat) across its native range. Cutthroat conservation policy hinges on the degree to which populations are hybridized, yet little is known about differences in the life history of individuals with varying degrees of rainbow trout ancestry. We examined differences in growth, fecundity, and migration timing between cutthroat and hybrid trout in migratory components of populations from 2006 to 2009 in the Jocko River, Montana. We detected positive linear relationships between rainbow trout ancestry and somatic growth and egg size, but a negative relationship with fecundity. US federal policy suggests a threshold of 20% rainbow ancestry for cutthroat conservation. In our study, hybrids with ≥20% rainbow trout ancestry had significantly lower fecundity and larger egg sizes and migrated earlier at lower discharges and stream temperatures than individuals with <20% rainbow trout ancestry. Our results did not indicate threshold changes but rather continuous differences associated with rainbow trout ancestry, suggesting that establishing a biologically relevant cutoff for conservation purposes will be problematic. [ABSTRACT FROM AUTHOR]

Timing of spawning and hatching of shortnose sturgeon, Acipenser brevirostrum, in the Saint John River, New Brunswick, Canada, was estimated using inverse prediction. We examined egg incubation periods at 5, 9, and 13 °C to back-calculate spawning dates. No larvae hatched at 5 °C. At 9 and 13 °C, hatching began after 18 and 8 days post fertilization, respectively. Lengths of yolk-sac larvae reared in the laboratory at 13-21 °C were used to develop a temperature-mediated Gompertz growth model. The inverted Gompertz model, predicting larval age from larval size and water temperature, was applied to 671, 164, and 746 larvae captured in the wild in 2008, 2009, and 2010, respectively. Estimated hatching distributions peaked in late May, and mean spawning events were predicted to occur in late April - early May (9 °C scenario) and middle to late May (13 °C scenario). Larval ages at the two sampling transects, 4.5 km apart, were similar, while catch per unit effort was lower downstream, indicating mortality during dispersal. Inverse prediction of larval ages provides fast and cost-effective estimates of the timing of spawning, hatching, and larval migration in the wild. [ABSTRACT FROM AUTHOR]

Skipjack (SJT) (Katsuwonus pelamis) is a medium-sized, pelagic, highly dispersive tuna species that occurs widely across tropical and subtropical waters. SJT constitute the largest tuna fishery in the Indian Ocean and are currently managed as a single stock. Patterns of genetic variation in a mtDNA gene and six microsatellite loci were examined to test for stock structure in the northwestern Indian Ocean. 324 individuals were sampled from five major fishing grounds around Sri Lanka and from single sites in the Maldive Islands and the Laccadive Islands. Phylogenetic reconstruction of mtDNA revealed two coexisting divergent clades in the region. Analysis of molecular variance (AMOVA) of mtDNA data revealed significant genetic differentiation among sites (ΦST = 0.2029, P < 0.0001), also supported by spatial AMOVA results. AMOVA of microsatellite data also showed significant differentiation among most sampled sites (FST = 0.0256, P < 0.001), consistent with the mtDNA pattern. STRUCTURE analysis of the microsatellite data revealed two differentiated stocks. While both marker types examined identified two genetic groups, microsatellite analysis indicates that the sampled SJT are likely to represent individuals sourced from discrete breeding grounds that are mixed in feeding grounds in Sri Lankan waters. La thonine à ventre rayé (SJT) (Katsuwonus pelamis) est une espèce de thon de taille moyenne, à vie pélagique et à grand pouvoir de dispersion qui est largement répandue dans les eaux tropicales et subtropicales. Les SJT représentent la pêche commerciale de thons la plus importante dans l'Océan Indien et elles sont gérées actuellement comme un seul stock. Nous avons examiné les patrons de variation génétique dans un gène de l'ADNmt et dans six locus microsatellites afin de déterminer la structure des stocks dans le nord-ouest de l'Océan Indien. Nous avons prélevé 324 individus dans cinq importantes zones de pêche au large du Sri Lanka ainsi que dans des sites isolés aux îles Maldives et aux îles Laquedives. La reconstruction phylogénétique de l'ADNmt révèle la coexistence de deux clades divergents dans la région. Une analyse de variance moléculaire (AMOVA) des données d'ADNmt montre une différentiation génétique significative entre les sites (ΦST = 0,2029, P < 0,0001), ce qui est aussi confirmé par les résultats d'une AMOVA spatiale. Une AMOVA des données des microsatellites montre aussi une différentiation significative entre la plupart des sites échantillonnés (FST = 0,0256, P < 0,001) qui est compatible avec la structure basée sur l'ADNmt. Une analyse STRUCTURE des données des microsatellites indique deux stocks différentiés. Bien que les deux types de marqueurs utilisés identifient deux groupes génétiques, l'analyse des microsatellites indique que les SJT échantillonnés représentent des individus provenant d'aires de fraie discrètes qui se mêlent sur les aires d'alimentation dans les eaux du Sri Lanka. [ABSTRACT FROM AUTHOR]

A laboratory study was undertaken to investigate whether Northeast Atlantic herring (Clupea harengus), i.e., Norwegian spring-spawning herring, exhibit a “sensitive period” during the feeding season in which ovary development is particularly susceptible to food availability and (or) energy reserves. Groups of herring received similar amounts of food over the restricted summer – early autumn feeding season but the food availability was varied temporally between groups. The herring, an extreme capital breeder, did not exhibit a sensitive period, as there was no difference in fecundity or ovary maturation between groups. However, individuals that did not reach a Fulton’s condition factor (K) above 0.70 during the feeding season were less likely to begin ovary maturation. Those below this threshold showing ovary development began later and had a higher intensity of atresia than fish in better condition. To maximize fecundity, females recruited significantly more oocytes than they could support through to spawning, thus the oocytes were subsequently down-regulated. Some would have skipped spawning in the coming spawning season; these fish had a very low K. Taken together, this study demonstrates that this capital breeder has developed a suite of reproductive strategies to synchronize the production of the highest number of eggs energetically possible. [ABSTRACT FROM AUTHOR]

Atlantic herring (Clupea harengus) have contrasting spawning strategies, with apparently genetically similar fish “choosing” different spawning seasons, different egg sizes, and different spawning areas. In the North Sea, both autumn- and winter-spawning herring share the same summer feeding area but have different spawning areas. Females of both spawning types start their oocyte development in April–May. Oocyte development is influenced by the body energy content; during the maturation cycle, fecundity is down-regulated through atresia in relation to the actual body condition. Hence, fecundity estimates must account for the relative time of sampling. The down-regulation over the whole maturation period is approximately 20% in autumn- and 50% in winter-spawning herring. The development of the oocytes is the same for both spawning strategies until autumn when autumn spawners spawn a larger number of small eggs. In winter spawners, oocyte development and down-regulation of fecundity continues, resulting in larger eggs and lower number spawned. In theory, autumn and winter spawners could therefore switch spawning strategies, indicating a high level of reproductive plasticity. [ABSTRACT FROM AUTHOR]

Deepwater dogsharks (Order Squaliformes) are thought to be particularly vulnerable to overfishing due to life history strategies that place them at the lower end of the shark productivity spectrum. Sharks frequently have relatively low value in multispecies fisheries, where management is usually aimed at maintaining harvest of more valuable and productive teleosts. This results in low priority being given to data collection for sharks and hampers identification of appropriate harvest strategies. Here an age-structured model with maximum sustainable harvest rate (UMSY) as leading productivity parameter is systematically applied to show that for certain growth and reproductive schedules that apply to some sharks, the range of possible values that can be taken by UMSY can become very small. The model was applied to 12 Australian dogshark species and was used to show that UMSY is highly constrained under some selectivity schedules. Results were consistent with estimates of the intrinsic rate of growth obtained using a demographic model, suggesting that there may be more certainty about UMSY than expected for many shark species, given uncertainty in recruitment parameters. The approach could be used to inform policy for some sharks and may be useful in the development of informative Bayesian priors for assessment models. [ABSTRACT FROM AUTHOR]

Presents information on a study which developed a model that accounted for fecundity changes at the individual level and that could be used to estimate population egg production beyond the study period. Materials and methods of the study; Results of the study; Discussion on the study.

Examines stock-recruitment model that incorporates Allee effects, which may occur when fish populations are small. Analysis of two Pacific salmon populations; Effects of increasing density on fecundity and survival; Use of maximum likelihood approach with a global genetic search algorithm.

Determines, on a one-to-one basis, whether sild and captively reared males differ in their ability to acquire access to spawning females and fertilize eggs. Comparison of pairs of captively reared and wild males in isolated arenas to eliminate the potential for a few very dominant males to interfere with the interactions among other males; Importance of initial aggressive interactions in determining eventual spawning success.