Reproductive Biology and Fecundity Assessment in Marine Fishes

Reproductive biology in marine fishes encompasses the processes by which gametes develop, mature and are released, and the strategies by which spawning occurs. Oogenesis and spermatogenesis follow well‐defined histological stages, from primary growth through vitellogenesis to final maturation. Fecundity assessment estimates the number of eggs produced per spawning event or season, classified as determinate when oocyte recruitment ceases before spawning, or indeterminate when recruitment continues throughout the spawning season. Core metrics such as the gonadosomatic index (GSI), batch fecundity and relative fecundity inform stock assessments and management decisions. Techniques range from macroscopic staging and stereological counts to advanced histological imaging and egg production methods. A global understanding of these processes underpins sustainable fisheries management, conservation planning and the forecasting of population resilience under environmental change.

Research from Nature Portfolio

Recent studies have challenged binary views of fecundity by demonstrating that oocyte recruitment patterns are more nuanced than determinate versus indeterminate classifications suggest. Application of oocyte packing density theory in a commercially important teleost revealed that primary oocyte pools predetermine fecundity at an earlier developmental stage than previously thought, prompting a reevaluation of spawning potential estimations. In another investigation, de novo recruitment of late previtellogenic oocytes into the vitellogenic pool was documented in a serial spawner, leading to a revised lower size threshold for fecundity counts and a clearer distinction of true indeterminate spawning. Additionally, a novel ultrametric method based on the ratio of vitellogenic to previtellogenic oocytes has been introduced to categorise spawning progression in batch spawners, offering a largely automated alternative to traditional histology that accommodates bimodal oocyte distributions and variable spawning intervals.

Reproductive Biology and Fecundity Assessment in Marine Fishes publication trend

The graph below shows the total number of articles in reproductive biology and fecundity assessment in marine fishes across all publications each year (not limited to Nature Index journals).

Technical terms

Fecundity: The number of mature eggs a female fish produces per spawning event or season.

Determinate fecundity: A spawning strategy where the full complement of eggs is recruited before spawning begins, with no further oocyte recruitment during the spawning season.

Indeterminate fecundity: A spawning strategy characterised by continuous oocyte recruitment throughout the spawning period, leading to variable batch fecundity.

Gonadosomatic index (GSI): The ratio of gonad weight to total body weight, expressed as a percentage, used to infer reproductive condition.

Daily Egg Production Method (DEPM): An egg‐production–based approach that estimates spawning stock biomass by measuring daily egg output and accounting for egg mortality and spawning duration.

References

1. Large sardine resource discovered off south-eastern Australia: Potential risks, challenges and benefits of establishing a new fishery. Marine Policy (2023).
2. MSCF: Multi-Scale Canny Filter to Recognize Cells in Microscopic Images. Sustainability (2023).
3. New insights in oocyte dynamics shed light on the complexities associated with fish reproductive strategies. Scientific Reports (2019).
4. Development of a new ‘ultrametric’ method for assessing spawning progression in female teleost serial spawners. Scientific Reports (2020).
5. First thorough assessment of de novo oocyte recruitment in a teleost serial spawner, the Northeast Atlantic mackerel (Scomber scombrus) case. Scientific Reports (2021).
6. Standard histological techniques systematically under‐estimate the size fish start spawning. Fish and Fisheries (2022).
7. A Standardized Terminology for Describing Reproductive Development in Fishes. Marine and Coastal Fisheries (2011).