Bonga shad (Ethmalosa fimbriata) spawning tactics in an upwelling environment

Abstract

Successful recruitment in small pelagic fish populations inhabiting upwelling zones is subject to variation in fecundity and is driven by spatial and temporal fluctuations in environmental conditions, that is, mainly sea surface temperature, salinity and food availability. These fluctuations in abiotic factors have stimulated small pelagic fish populations to exhibit specifically adapted spawning tactics. To better understand to what extent a short‐lived exploited fish species such as bonga shad Ethmalosa fimbriata has adapted to an upwelling environment, we have investigated the interrelationship between upwelling intensity as a proxy for productivity and population fecundity by means of a virtual population analysis. We found that females of intermediate size contributed significantly more eggs to the population's fecundity than smaller or larger ones. Our model results further indicate that E. fimbriata exhibits a spawning preference at water temperatures of around 25°C and upwelling intensities of around 2.5 m3 s−1 m−1. Hence, we hypothesize that climate change‐driven increases in sea temperatures and modifications of upwelling‐favourable winds could significantly impact the species’ reproductive biology. To understand how climate change might impact fisheries, spawning tactics of small pelagic fishes are important to assess as well as their recruitment success. Such information is particularly relevant in countries where the fishery is critical at socio‐economic level, to better implement fisheries management addressing multiple stressors.

Population Structure, Age and Growth of Sardine (Sardina pilchardus, Walbaum, 1792) in an Upwelling Environment

“…According to Hattab et al [87] and Basilone et al [88,89], environmental changes may have impacts on the size and fecundity of small pelagic species. These results were also confirmed by Baldé et al [4,6] in West Africa. Indeed, growth is strongly influenced by environmental variations which lead to a decrease or increase in fecundity of small pelagics in Senegal.…”

“…The biological parameters of small pelagic fishes are expected to differ with habitat, environment factors, and overfishing [3,4,6]. The current study showed that the asymptotic length (L ∞ ) of S. pilchardus was 30.5 cm maximum at six years, and that this value differed significantly to other countries in northwest Africa (Table 2).…”

“…In addition to environmental factors, high rates of fishing mortality alter population structure and growth rates of many pelagic fishes [4,6,9]. Voulgaridou and Stergiou [9] showed that a decrease in S. pilchardus body size from 1996 to 2000 corresponded to a sharp increase in sardine landings from 1992 to 1997 in the Mediterranean Sea (Greece).…”

“…Growth parameters vary in time and space, depending on parental condition (e.g., weight and condition), food availability (abundance and quality), environmental parameters (temperature and salinity), and evolutionary stressors (e.g., density, fishing pressure) [3][4][5]. Thus, information obtained from growth parameters could help identify the adaptation strategies and environmental conditions of a given species [6], facilitating the modeling of population dynamics and impacts of anthropogenic factors for many fisheries considered poor in data [7].…”

Spawning strategy of Japanese anchovy Engraulis japonicus in the coastal Yellow Sea: Choice and dynamics

“…Previous studies have demonstrated the importance of oceanographic structures to these spawning activities, as well as the direct effects of temperature, salinity and other abiotic factors (Bakun, 2006; Brunel et al., 2017; Kloppmann et al., 2001; Lough et al., 1996). For example, most of the intense spawning areas of SPF appear within regions of high zooplankton productivity, which are associated with the main upwelling areas or meso‐scale hydrodynamic structures such as eddies and ocean fronts (Aceves‐Medina et al., 2009; Baldé et al., 2019; Peck et al., 2013; Somarakis & Nikolioudakis, 2007). However, some SPF use different spawning strategies to avoid the strong passive transport of their eggs and larvae or the strong turbulence and instability of the water column in some intense upwelling systems (Dias et al., 2014; Lluch‐Belda et al., 1991; Parrish et al., 1981; Tiedemann et al., 2017), suggesting that SPF show adaptive phenotypic characteristics in different oceanographic systems.…”