Emerging issues and methodological advances in fisheries reproductive biology

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 following needs: (1) to employ standardization, thereby improving our ability to conduct comparative studies; (2) to better understand patterns of gonadal development and spawning events over time; and (3) to move beyond the spawning stock biomass paradigm. We identify the contributions of special section papers to these topics and conclude by suggesting needsThis workshop was jointly sponsored by FRESH (COST Action FA0601; www.fresh-cost.org) and the AFS Marine Fisheries Section.Peer reviewe

A standardized terminology for describing reproductive development in fishes

19 páginas, 12 figuras, 3 tablas.-- Open access journalAs 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 capable phase includes (1) those fish with gamete development that is sufficiently advanced to allow for spawning within the current reproductive cycle and (2) batch-spawning females that show signs of previous spawns (i.e., postovulatory follicle complex) and that are also capable of additional spawns during the current cycle. Within the spawning capable phase, an actively spawning subphase is defined that corresponds to hydration and ovulation in females and spermiation in males. The regressing phase indicates completion of the reproductive cycle and, for many fish, completion of the spawning season. Fish in the regenerating phase are sexually mature but reproductively inactive. Species-specific histological criteria or classes can be incorporated within each of the universal phases, allowing for more specific divisions (subphases) while preserving the overall reproductive terminology for comparative purposes. This terminology can easily be modified for fishes with alternate reproductive strategies, such as hermaphrodites (addition of a transition phase) and livebearers (addition of a gestation phase)Fish Reproduction and Fisheries (FRESH; European Cooperation in Science and Technology Action FA0601) and theWest Palm Beach Fishing Club (Florida) provided funding for the gonadal histology workshops where this terminology was developed and refined. Additionally, we thank FRESH for travel and publication fundsPeer reviewe

Sex-Specific Growth and Reproductive Dynamics of Red Drum in the Northern Gulf of Mexico

The Red Drum Sciaenops ocellatus stock is heavily targeted in the Gulf of Mexico (GOM) by recreational fishers and supports a small commercial fishery in Mississippi. Despite their popularity, little recent work has been done to describe their life history. In this work, we describe sex‐specific growth and reproductive dynamics of Red Drum collected from the northern GOM from September 2016 through October 2017. We evaluated seven candidate growth models and found that the three‐parameter von Bertalanffy growth function (VBGF) was the best candidate length‐at‐age model. No significant difference in growth between sexes was observed with the three‐parameter VBGF, despite the female‐specific curve having a larger mean asymptotic length than the male‐specific curve. All seven candidate growth models predicted similar mean length‐at‐age estimates, and four of them exhibited significant differences in sex‐specific mean length at age, with females reaching a larger length at age than males after age 5. There was no significant difference between the sex‐specific weight‐at‐length relationships. Red Drum are batch spawners that spawn in northern GOM coastal waters during August and September. We estimated 3.7 d between spawns and 10.5 spawning events per female in 2017. Nearly 20% of fish collected during the spawning season were sexually mature but reproductively inactive, indicating the possibility of skipped spawning. The age at 50% maturity was around 3 years (length at 50% maturity = 670 mm TL) in both sexes, but fish were not spawning capable until age 4.5 (703 mm TL) in males and age 5.8 (840 mm TL) in females. Furthermore, elevated gonadosomatic indices were not observed until around age 5–6. The updated life history information presented in this work helps to address current data limitations and provides critical information for future assessments of Red Drum stocks in the northern GOM

The ocean’s movescape: Fisheries management in the bio-logging decade (2018–2028)

Although movement has always played an important role in fisheries science, movement patterns are changing with changing ocean conditions. This affects availability to capture, the spatial scale of needed governance, and our food supply. Technological advances make it possible to track marine fish (and fishermen) in ways not previously possible and tracking data is expected to grow exponentially over the next ten years – the bio-logging decade. In this article, we identify fisheries management data needs that tracking data can help fill, ranging from: improved estimates of natural mortality and abundance to providing the basis for short-term fisheries closures (i.e. dynamic closures) and conservation of biodiversity hotspots and migratory corridors. However, the sheer size of the oceans, lack of GPS capability, and aspects of marine fish life history traits (e.g., adult/offspring size ratios, high mortality rates) create challenges to obtaining this data. We address these challenges and forecast how they will be met in the next 10 years through increased use of drones and sensor networks, decreasing tag size with increased sensor capacity trends, the ICARUS initiative to increase satellite tracking capacity, and improved connectivity between marine and terrestrial movement researchers and databases.publishe

An improved and simplified terminology for reproductive classification in fishes

As the number of fish reproductive studies has proliferated, so has the number of gonadal classification schemes and terms. This has made it difficult for managers and scientists to communicate and for comparisons to be made between studies. We propose the adoption of a simple, universal terminology for the phases in the reproductive cycle that can be used with all male and female elasmobranch and teleost fishes. These phases were chosen because they define key milestones in the reproductive cycle representing critical parameters such as size at maturity, duration of spawning season, location and diel periodicity of spawning, and fecundity. The phases we propose include: Immature, Developing, Spawning Capable, Actively Spawning, Regressing and Regenerating. Although the histological criteria identifying each phase may vary for different species and phases may not always occur sequentially, each phase is conceptually universal. The Immature phase can only occur once. The Developing phase signals entry into the gonadotropindependent stage of oogenesis and spermatogenesis and gonadal growth. The Spawning Capable phase indicates fish that will spawn this season because development within ovaries (fully grown vitellogenic oocytes) or testes (spermatozoa in lumens/ducts) is sufficiently advanced. Actively Spawning females are those that show recent evidence of spawning (i.e., hydrated or ovulated oocytes). Females of many species cycle between the Spawning Capable and Actively Spawning phases during the reproductive season and these phases are necessary to determine fecundity, spawning frequency, location and diel periodicity. Spawning Capable and Actively Spawning phases are difficult to differentiate histologically in males. The Regressing phase indicates fish that are completing the spawning season. Fish in the Regenerating phase are sexually mature but reproductively inactive. We show how researchers can incorporate species-specific histological criteria or classes within each of the universal phases, allowing more specific divisions yet preserving the overall reproductive terminology for comparative purposes

A standardized terminology for describing reproductive development in fishes

6 páginas, 2 figurasPeer reviewe