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).…”

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

“…However, in sturgeons, manipulation of diet ration or nutritional content has been shown to affect growth, energetic status (Hung and Lutes 1987;Cui et al 1997;Hung et al 1997;Deng et al 2009;Han et al 2012;Haller et al 2015) and the cellular response to heat stress (Deng et al 2009;Han et al 2012;Wang et al 2013). Furthermore, diet composition and nutritional status have been shown to influence swimming capacity (Wagner et al 2004;Chatelier et al 2006;Wilson et al 2007;Gingerich et al 2010;Pettersson et al 2010;Killen et al 2014;Silva et al 2014), osmoregulation (Kirschner 1995;Tseng and Hwang 2008;Haller et al 2015), growth at high temperatures (Glencross and Rutherford 2010;Zhou et al 2013) and tolerance of high temperatures (Akhtar et al 2011;Kumar et al 2014;Patterson and Green 2014;Tejpal et al 2014) for a wide range of fish species.…”

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

“…The time spent swimming and the foraging behaviour of sardine larvae increased with age/size. The increase in the frequency of prey capture with age/size is a consequence of larger larvae swimming faster (Silva et al 2014) and being able to capture prey within a wider size range (Caldeira et al 2014). By being able to select larger prey, larger larvae maximize the net rate of energy gain, because, all other things being equal, larger prey yield more energy per unit effort.…”

“…4, Table 4). The ontogenetic increase in the swimming ability of sardine larvae matches the timing of notochord flexion (Silva et al 2014), coinciding with the beginning of the caudal fin formation and development of the swim bladder (Santos et al 2007). This ontogenetic event also marks the time when foraging abilities (number of orientations and attacks on prey and percent success in capturing prey) sharply in creased, which was more abrupt for larvae reared at 17°C than for larvae reared at 15°C.…”

“…and nauplii, copepodites and adults of the copepod Paracartia grani. Details of the feeding conditions, which translate into saturated feeding and growth rates of sardine larvae, can be found in Silva et al (2014) and Caldeira et al (2014). Each morning, after checking the food concentration in the tanks, 20 to 30% of the tank water was renewed by syphoning the bottom of the tank, and new food was added to obtain the preestablished food concentration.…”