Abstract
Summary The African halfbeak Hyporhamphus picarti (Hemiramphidae) is one of the most abundant species within the ichthyoplankton community of the Sine Saloum estuary (Senegal). A year-round occurrence of larvae suggests that the Sine Saloum is an important spawning habitat for this species. Annual fluctuations in water temperature, however, can have severe impacts on the survival probabilities of marine fish larvae. To determine whether temperature has an effect on the growth of H. picarti during its larval development, larval age at length and somatic growth rates were investigated for two contrasting spawning seasons in 2014: February (cold season, 20.8°C) and June (warm season, 26.4°C). In both months H. picarti larvae were sampled at the mouth of the Saloum River using neuston nets. Sagittal otoliths’ increments were counted to estimate the larva age at a given standard length (SL). The age of larvae ranged between 2 and 22 days, with SL of 3.86–21.68 mm, respectively. In order to describe larval age at length during the contrasting spawning seasons, two distinctive Gompertz functions were applied. Accordingly, specimens sampled in June (0.94 ± 0.17 mm per day) exhibited significantly higher somatic growth rates than those sampled in February (0.60 ± 0.06 mm per day). These findings suggest that water temperature is an important factor influencing larval growth in H. picarti. Information concerning the early life stages of H. picarti are scarce and the results of the present study may contribute to a better understanding of the species’ biology and ecology.
Highlights
Temperature fluctuations can have severe effects on the early life stages of marine fishes. These effects on larval survival can be either indirect by altering the primary production of the ecosystem and food availability (Vidy, 2000), or direct by affecting the metabolism and various physiological processes which influence the growth in fishes (Green & Fisher, 2004)
Since growth rates are positively correlated with water temperature, it can be concluded that this parameter is the major factor influencing survival probabilities of marine fish early life stages (Houde, 1989)
Direct effects of water temperature on somatic growth and survival in marine fish larvae are generally regarded as stronger than the indirect ones exhibited by enhanced food availability (Houde, 2008)
Summary
Temperature fluctuations can have severe effects on the early life stages of marine fishes These effects on larval survival can be either indirect by altering the primary production of the ecosystem and food availability (Vidy, 2000), or direct by affecting the metabolism and various physiological processes which influence the growth in fishes (Green & Fisher, 2004). Since growth rates are positively correlated with water temperature, it can be concluded that this parameter is the major factor influencing survival probabilities of marine fish early life stages (Houde, 1989). The family Hemiramphidae is one of the five families of the order Beloniformes, which populate the warm waters of the Pacific, the Indian Ocean and the Atlantic (Collette, 2004) Individuals of this family generally exhibit rapid growth rates and reach sexual maturity during the first year of their life (McBride & Thurman, 2003). We used sagittal otoliths to compare somatic growth rates between the two seasons
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