Ontogeny of swimming behaviour in sardine Sardina pilchardus larvae and effect of larval nutritional condition on critical speed

Abstract

The ontogeny of swimming behaviour in sardine Sardina pilchardus larvae was studied, from hatching to 75 days post-hatch (dph), by measuring the critical swimming speed (U crit ) and observing locomotory behaviour. In addition, the effect of larval nutritional condition on U crit at the onset of their swimming abilities (20 to 25 dph) was evaluated by rearing larvae under 4 different feeding treatments. Diets consisted of different concentrations of dinoflagellates, rotifers and the copepod Acartia grani, and a wild plankton assemblage. Recently hatched larvae were mostly inactive, but from 2 dph onwards larvae started to swim freely in the rearing tank, and time spent swimming increased throughout ontogeny. Larvae younger than 20 dph (i.e. < 7.90 mm TL) could not swim for the entire adjustment period at the minimum current speed, but thereafter U crit increased significantly with larval age and length, reaching a maximum of 9.47 cm s −1 at 19.10 mm TL and 55 dph. Growth, survival and the nutritional condition of sardine larvae, assessed by the RNA residual index, were significantly higher for larvae reared with the high-concentration diet, contrary to the other derived nucleic acids indices (RNA/DNA and DNA/DW), which showed no differences between diets. Despite differences in the survival and growth rates of sardine larvae, U crit at the onset of swimming did not differ significantly among diets, but was significantly related to larval nutritional condition as assessed by the RNA residual index. Overall, our results show that early larval stages of sardines have poor swimming ability and probably rely on food patches in the wild to survive; however, close to metamorphosis (especially from 45 dph onwards), larvae spend most of the time swimming and are capable of resisting the mean current speeds of their natural environment, which may strongly enhance chances for survival. KEY WORDS: Ontogeny • Critical swimming speed • U crit • Sardina pilchardus • Nucleic acid derived indices • RNA/DNA • Foraging Resale or republication not permitted without written consent of the publisher

Bounded and unbounded boundaries – Untangling mechanisms for estuarine-marine ecological connectivity: Scales of m to 10,000 km – A review

“…For typically at least one week after spawning in coastal waters the eggs and larvae of these fish and prawns are passive and advected by the water currents (Rothlisberg et al, 1995;Faria et al, 2011;Silva et al, 2014;Wolanski and Elliott, 2015). If there is a net longshore current, they are dispersed away from the coastal spawning areas (Figure 6a).…”

Effect of temperature on the growth, survival, development and foraging behaviour of Sardina pilchardus larvae

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Effects of nutritional deprivation on juvenile green sturgeon growth and thermal tolerance

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