Reproductive biology and fecundity of the Bay of Biscay anchovy population (Engraulis encrasicolus L.)
Lorenzo Motos

This review presents the results of field studies conducted between 1987 and 1992 on the on reproductive biology and fecundity of the Bay of Biscay anchovy. Close to 100% of the anchovy population reach maturity during the reproductive season, although the smallest 1-year-old anchovy mature slightly later. At peak spawning, however, the reproductive output (numbers of eggs laid daily per unit body weight) of one year old anchovy is similar to that of older anchovy. Anchovy mainly spawn from 19:00 to 6:00 (GMT) with a peak at 00:00 (GMT). For the females spawning on a given night, the final maturation process of the spawning batch of oocytes starts the night before. The process of nuclear migration proceeds through the night and the first part of the following day. Oocytes start to hydrate early in the afternoon of the day of spawning. Hydration reaches its maximum intensity at dusk and in the early night. Gonads with postovulatory follicles can already be observed before dusk, indicating the start of spawning activities. Anchovy is a batch spawner with indeterminate fecundity. ‘De novo’ vitelogenesis proceeds in immature oocytes during the reproductive season. Annual fecundity is determined by both the number of eggs laid per spawning (batch fecundity) and the number of spawnings per season (frequency of spawning and duration of the spawning season). Batch fecundity presents an increasing pattern as the season advances, from ca. 200 eggs /g in April, to ca. 500 and ca. 650 eggs/g in May and June respectively. The fraction of females spawning per day ranges from 18 to 33%, and increases as the season progresses. This high spawning frequency may be related to the relatively short spawning season. Assuming a two month protracted spawning season, the total reproductive output of Bay of Biscay anchovy can range between ca 9,000 to ca. 11,000 eggs per unit gonad-free body weight (g).

Keywords: Anchovy, Engraulis encrasicolus, spawning, reproductive biology, fecundity, Bay of Biscay
Contents of this volume Sci. Mar. 60(Suppl.2) : 195-207 Back PDF
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