Linking the dynamic organization of the ovary with spawning dynamics in pelagic fishes

Abstract

The link between the dynamic organization of the ovary and spawning dynamics was investigated in pelagic fishes with indeterminate fecundity. Αn array of laboratory methods and statistical approaches was applied to samples of gonadal material from three commercial NE Atlantic fish species: the sardine, Sardina pilchardus, the horse mackerel, Trachurus trachurus, and the mackerel, Scomber scombrus. Methods included the application of clustering analysis algorithms in histological specimens and the application of particle analysis on whole mounts. More specifically, various attributes of ovarian dynamics such as the oocyte size frequency distribution, the ratio of total to batch fecundity, the number of oocyte cohorts, and the recruitment of early secondary growth oocytes were related to historic estimates of spawning interval and oocyte growth rate. It was shown that indeterminate spawners can display varying proportions of oocytes at the size range between primary and secondary growth based on the seasonal pattern of oocyte recruitment. This finding indicates that determinacy and indeterminacy should rather be recognized as end-points along a continuum which is controlled by the degree of overlap between oocyte recruitment period and spawning period. It was also demonstrated that fishes like sardine with long spawning intervals and fast oocyte growth exhibit relatively few, clearly separated oocyte cohorts, while fishes like mackerel with shorter spawning interval display increased number of coexisting cohorts. Ultimately, these aspects may provide a proxy of spawning interval and thereby spawning frequency which is a variable of paramount importance in biomass assessments of commercial fish stocks through egg production methods.

Latitudinally distinct stocks of Atlantic cod face fundamentally different biophysical challenges under on‐going climate change

“…One should, however, expect that the overall rate of vitellogenin uptake ( ∆ VDW overall ) would fall if a persistently high T is introduced prior to spawning due to the foreseen reduction in 17β‐estradiol in several species (Alix et al, 2020). Anyhow, our formulations confirmed that the teleost ovulatory cycle is highly complex in nature (Charitonidou et al, 2022); in cod probably at least two oocyte cohorts co‐develop. The further process of validation of ∆ VDW overall showed, however, clear examples of underestimates for larger individuals, suggesting that a much bigger share of the vitellogenic raw material is stored in muscle and liver in larger than smaller females (Jansen et al, 2021; Kjesbu et al, 1991).…”

“…One should, however, expect that the overall rate of vitellogenin uptake Cod spawning grounds displacement (∆VDW overall ) would fall if a persistently high T is introduced prior to spawning due to the foreseen reduction in 17β-estradiol in several species (Alix et al, 2020). Anyhow, our formulations confirmed that the teleost ovulatory cycle is highly complex in nature (Charitonidou et al, 2022); in cod probably at least two oocyte cohorts co-develop.…”

Quantitative Analysis of Ovarian Dynamics of European Sardine Sardina pilchardus (Walbaum, 1792) during Its Spawning Period

“…However, environmental conditions such as temperature and food availability and parameters such as fish condition can act synergistically and affect reproductive characteristics (oocyte size, oocyte recruitment, spawning frequency, batch fecundity, duration of spawning period, etc. ), thus influencing a fish population's reproductive outcomes [18,34,36,[39][40][41][42][43]. Knowledge of ovarian dynamics and how they are influenced by environmental factors is very important, not only for applying egg production methods for fisheries stock assessments and management [44,45] but also for understanding and predicting impacts of climate change.…”