As the number of fish reproduction studies has proliferated, so has the number of gonadal classification schemes and terms. This has made it difficult for both scientists and resource managers to communicate and for comparisons to be made among studies. We propose the adoption of a simple, universal terminology for the phases in the reproductive cycle, which can be applied to all male and female elasmobranch and teleost fishes. These phases were chosen because they define key milestones in the reproductive cycle; the phases include immature, developing, spawning capable, regressing, and regenerating. Although the temporal sequence of events during gamete development in each phase may vary among species, each phase has specific histological and physiological markers and is conceptually universal. The immature phase can occur only once. The developing phase signals entry into the gonadotropin-dependent stage of oogenesis and spermatogenesis and ultimately results in gonadal growth. The spawning cap...

https://afspubs.onlinelibrary.wiley.com/doi/pdf/10.1080/19425120.2011.555724

A Standardized Terminology for Describing Reproductive Development in Fishes

Oogenesis in fishes follows a universal plan; yet, due to differences in the synchrony and rate of egg development, spawning frequency varies from daily to once in a lifetime. Some species spawn and feed in separate areas, during different seasons, by storing energy and drawing on it later for reproduction (i.e. capital breeding). Other species spawn using energy acquired locally, throughout a prolonged spawning season, allocating energy directly to reproduction (i.e. income breeding). Capital breeders tend to ovulate all at once and are more likely to be distributed at boreal latitudes. Income breeding allows small fish to overcome allometric constraints on egg production. Income breeders can recover more quickly when good-feeding conditions are re-established, which is a benefit to adults regarding bet-hedging spawning strategies. Many species exhibit mixed capital- and income-breeding patterns. An individual's position along this capital–income continuum may shift with ontogeny or in relation to environmental conditions, so breeding patterns are a conditional reproductive strategy. Poor-feeding environments can lead to delayed maturation, skipped spawning, fewer spawning events per season or fewer eggs produced per event. In a few cases, variations in feeding environments appear to affect recruitment variability. These flexible processes of energy acquisition and allocation allow females to prioritize their own condition over their propagules' condition at any given spawning opportunity, thereby investing energy cautiously to maximize lifetime reproductive value. These findings have implications for temporal and spatial sampling designs, for measurement and interpretation of fecundity, and for interpreting fishery and ecosystem assessments.

/pdf/energy-acquisition-and-allocation-to-egg-production-in-331aqp6cge.pdf

Energy acquisition and allocation to egg production in relation to fish reproductive strategies

Reproductive timing can be defined as the temporal pattern of reproduction over a lifetime. Although reproductive timing is highly variable in marine fishes, certain traits are universal, including sexual maturity, undergoing one or more reproductive cycles, participating in one or more spawning events within a reproductive cycle, release of eggs or offspring, aging, and death. These traits commonly occur at four temporal scales: lifetime, annual, intraseasonal, and diel. It has long been known that reproductive timing affects reproductive success, especially in terms of the onset of sexual maturity and the match or mismatch between seasonal spawning and offspring survival. However, a comprehensive understanding of variability in reproductive timing over species, populations, and temporal scales is lacking. In addition, there is a need to assess how variability in reproductive timing affects a population's resilience. Because natural selection occurs at the individual level, this necessitates an ...

/pdf/reproductive-timing-in-marine-fishes-variability-temporal-20b7lli008.pdf

Reproductive Timing in Marine Fishes: Variability, Temporal Scales, and Methods

Although incorporating detailed reproductive data into all stock assessments is not a practical goal, the need to understand how reproductive biology affects population productivity is being increasingly recognized. More research focused on reproductive biology—coupled with a shift towards a resilience perspective in fisheries science—is resulting in challenges to many long-held assumptions; the emergence of important new issues; and identification of the need to improve data and methods used in reproductive studies. Typically, data for reproductive studies are based on an assessment of gonadal development, which is most accurately evaluated with histology. This special section of Marine and Coastal Fisheries contains contributions from a workshop on the gonadal histology of fishes that was held in Cadiz, Spain, during June 2009. These papers cover a wide range of species and reproductive topics while introducing improved and new histological techniques. In this introduction, we address the follo...

/pdf/emerging-issues-and-methodological-advances-in-fisheries-2di1o9wqy0.pdf

Emerging Issues and Methodological Advances in Fisheries Reproductive Biology

https://backend.orbit.dtu.dk/ws/files/151765016/rutgers_lib_53378_PDF_1.pdf

Managing living marine resources in a dynamic environment: The role of seasonal to decadal climate forecasts

The traditional view of iteroparity in fishes is one of an annual reproductive cycle that culminates each year in spawning. More recently, a more flexible view of fish reproduction has been adopted, including the potential for mature fish to skip spawning. Here, we review the abundance of recent research on skipped spawning, covering a broad range of fishes with diverse life history strategies. Evidence for skipped spawning has been collected by use of traditional histological techniques as well as modern technological advances, such as satellite tags and the ability to track fish movements based on elemental and isotope signatures. Skipped spawning is most commonly attributed to deficient diet and poor nutritional condition. Advances made in this field of study in recent years include descriptions of hormonal changes that precede and perhaps initiate skipped spawning, the development of life history models that incorporate the potential for skipped spawning, and estimates of the degree to which ...

/pdf/skipped-spawning-in-fishes-more-common-than-you-might-think-4gudnfl3p1.pdf

Skipped Spawning in Fishes: More Common than You Might Think

Effect of age and temperature on spawning time in two gadoid species

Gametes from five male and three female haddock ( Melanogrammus aeglefinus ) were crossed to produce 15 half-sibling families that were used to evaluate potential parental contributions to early life history variability. Larval morphology at 0 and 5 days post-hatch (dph) and time to starvation in the absence of food were examined. Maternal influences on larval standard length and yolk area were significant at 0 and 5 dph. Paternal effects on larval standard length were significant at 0 and 5 dph, whereas paternal effects on yolk area were only significant at 5 dph. Larval eye diameter was influenced by maternity at day 0 post-hatch and by both maternity and paternity at 5 dph. Myotome height of larvae was subject to maternal and paternal influences at 0 and 5 dph. Growth rate was significantly influenced by both paternity and maternity. Yolk utilization efficiency was significantly influenced by parental interaction, while the time taken for larvae to die in the absence of food was affected only by maternity. Results of this study not only confirm the importance of female contributions to larval development but also indicate a paternal influence on the development and the early life history success of marine fish.

Parental effects on early life history traits of haddock Melanogrammus aeglefinus

Understanding the processes shaping population structure and reproductive isolation of marine organisms can improve their management and conservation. Using genomic markers combined with estimation of individual ancestries, assignment tests, spatial ecology, and demographic modeling, we (i) characterized the contemporary population structure, (ii) assessed the influence of space, fishing depth, and sampling years on contemporary distribution, and (iii) reconstructed the speciation history of two cryptic redfish species, Sebastes mentella and S. fasciatus. We genotyped 860 individuals in the Northwest Atlantic Ocean using 24,603 filtered single nucleotide polymorphisms (SNPs). Our results confirmed the clear genetic distinctiveness of the two species and identified three ecotypes within S. mentella and five populations in S. fasciatus. Multivariate analyses highlighted the influence of spatial distribution and depth on the overall genomic variation, while demographic modeling revealed that secondary contact models best explained inter- and intragenomic divergence. These species, ecotypes, and populations can be considered as a rare and wide continuum of genomic divergence in the marine environment. This acquired knowledge pertaining to the evolutionary processes driving population divergence and reproductive isolation will help optimizing the assessment of demographic units and possibly to refine fishery management units.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/eva.13143

Population genomics and history of speciation reveal fishery management gaps in two related redfish species ( Sebastes mentella and Sebastes fasciatus ).

Growth and condition in fishes have been taken as indicating levels of energy available for survival and reproduction, major components of a population’s productivity. After a rapid collapse in population size, northern (NAFO Division 2J3KL) cod (Gadus morhua) remained at a very low level of abundance for 20 years. We investigated the potential for poor growth and condition to have played a role in the collapse and lack of recovery of northern cod. Juveniles and adult males and females all showed similar patterns. Perceptions about the importance of growth and condition to population status depended on the metrics and area examined. When the northern cod population was declining, the northern areas of the population clearly had reduced growth and condition, while these metrics improved in the south. Results were equivocal as to the potential role of growth and condition in the continued low abundance of northern cod and, to some extent, depended on the nature of the metric being examined. Indices of condition, which included lipid storage in the form of liver weight, were generally lower in the north while the stock remained at a low level. Metrics associated with longer-term protein storage returned to precollapse levels quickly following the period of collapse. An index of food availability was more closely related to growth and condition than was temperature. These results point to the need both for studies of growth and condition in a population to have a comprehensive time-series of data covering the entire range of the population and the need for a better understanding of the causes and implications of changes in different metrics of condition.

/pdf/growth-and-condition-in-relation-to-the-lack-of-recovery-of-2o6qfcss7y.pdf

Rick M. Rideout

Papers

Skipped Spawning in Fishes: More Common than You Might Think

Effect of age and temperature on spawning time in two gadoid species

Parental effects on early life history traits of haddock Melanogrammus aeglefinus

Population genomics and history of speciation reveal fishery management gaps in two related redfish species ( Sebastes mentella and Sebastes fasciatus ).

Growth and condition in relation to the lack of recovery of northern cod