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

Abstract

Fish with indeterminate fecundity spawn multiple times throughout a protracted reproductive period. During that period several ovulation events succeed one another, and different oocyte developmental stages co-occur in the ovaries with new oocytes consistently recruiting from one growth phase to the next to form the sequential batches. In this study, we examined in detail the oocyte recruitment and development pattern of the sequential batches in a commercially important fish with indeterminate fecundity, the European sardine. The numbers and sizes of oocytes at different developmental stages were estimated for four phases of the ovulatory cycle (ovarian stages) and during the main spawning season (November–March) by applying the oocyte packing density theory in combination with stereological techniques. General linear models (GLMs) were used to test for changes in oocyte sizes as well as relative oocyte numbers per developmental stage within the different ovarian stages in the successive spawning months. A temporal association between several transition events of the oocyte development process was revealed. Specifically, the final maturation of the advanced batch triggered (a) the recruitment of oocytes from primary to secondary growth phase, (b) de novo vitellogenesis and (c) a surge of yolk deposition in primary vitellogenic oocytes. Oocyte recruitment was completed two days after the ovulation of the advanced batch and relative numbers of primary and secondary growth oocytes were thereafter stable until the next final maturation event. This pattern of oocyte recruitment and growth remained unchanged during the course of the spawning season. This study advances our knowledge on oocyte recruitment and development in fish with indeterminate fecundity, which is key to understanding reproduction and its drivers at the individual and population level.

Impact of Modern Oven Treatments on Lipid Oxidation and Vitamin E Content of Fillets from Sardine (Sardina pilchardus) at Different Reproductive Cycle Phases

“…Preventive nutrition is a strong tool to restrain metabolic diseases such as obesity and diabetes. A relevant and affordable food source of multiple bioactive compounds (minerals, proteins, vitamins, and essential fatty acids) is sardine ( Sardina pilchardus , Walbaum, 1792), which is a fast-growing species, a batch spawner with a protracted spawning season and short-life cycle [ 1 , 2 , 3 ]. This species is one of the most relevant pelagic fish of the Mediterranean Sea, especially the Adriatic Sea, due to its huge ecological to higher trophic levels at the bottom-up scale as sardines are considered important components of the food web [ 4 , 5 , 6 ]; due to its economic roles [ 3 , 7 ], with a global volume of 3.57 million tons in 2020, which remained stable in 2021–2026 [ 8 ]; and due to its nutritional value.…”