Historical fluctuations in spawning location of anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus) in the Bay of Biscay during 1967–73 and 2000–2004

Abstract

The spatial extent of small pelagic fish spawning habitat is influenced by environmental factors and by the state of the adult population. In return, the configuration of spawning habitat affects recruitment and therefore the future structure of the adult population. Interannual changes in spatial patterns of spawning reflect variations in adult population structures and their environment. The present study describes the historical changes in the spatial distribution of spawning of anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus) in the Bay of Biscay during two periods: 1967-72 and 2000-2004. Using data from egg surveys conducted in spring, the spatial distributions of anchovy and sardine eggs are characterized by means of geostatistics. For each survey, a map of probability of egg presence is constructed. The maps are then compared to define (1) recurrent spawning areas, (2) occasional spawning areas and (3) unfavourable spawning areas during each period. Sardine spawning habitat is generally fragmented and appears spatially limited by the presence of cold bottom water. It is confined to coastal or shelf break refuge areas in years of restricted spawning extent. For anchovy, recurrent spawning sites are found in Gironde and Adour estuaries whilst spawning can extend further offshore in years of more intense spawning. For both species, the mean pattern of spawning has changed between 1967-72 and 2000-2004. Noticeably, the spatial distribution of anchovy eggs in spring has expanded northward. This trend possibly results from changes in environmental conditions during the last four decades.

Modeling the Fate and Distribution of Floating Litter Particles in the Aegean Sea (E. Mediterranean)

“…To accomplish this, each cell was assigned to a category following the classification approach presented in Saraux et al (2014). This classification has been previously applied on multi-annual fish egg distribution data to characterize favorable spawning habitats (Bellier et al, 2007;Giannoulaki et al, 2013;Saraux et al, 2014). The approach assumes that cells with high mean and low standard deviation are considered as recurrent, signifying high concentration of litter particles for most of the years.…”

Climate, Anchovy, and Sardine

“…The anchoita is noteworthy for its close association with the Río de la Plata (de Macedo-Soares et al 2014). Many European anchovy stocks have river associations, e.g., in the Bay of Biscay (Bellier et al 2007), the northwest Mediterranean Sea (Agostini & Bakun 2002), and the Aegean Sea (Lloret et al 2004). The northern anchovy habitat includes water affected by the plume of the Columbia River (Emmett et al 2005).…”

“…Refugia are likely important for population survival at a small size (Lecomte et al 2004). Examples of refugia for current populations include the Galapagos for the Peruvian anchoveta (Bertrand et al 2004), the Pacific coast of Baja California for the Pacific sardine (Lluch-Belda et al 2003), and river plumes for the European sardine (Bellier et al 2007). …”

Growth of young-of-the-year European anchovy (<i>Engraulis encrasicolus</i>, L.) in the Bay of Biscay

“…In this region, anchovy spawns primarily in highly productive areas, such as the Gironde and Adour river plumes, and partially on the shelf break. The spawning season extends from March to August with a maximum intensity peak between May and June Bellier et al, 2007). The predominant north-easterly winds during summer transport larvae towards off-shelf waters.…”