Does Schooling Reduce Fast-start Response Latencies in Teleosts?

l. Response latencies. defined as the time between a d.c. electric shock and initiation of a fast-start (startle response) were measured for eight species of teleosts. 2. Fast-start response latencies varied from 10 to 36 cm. Highest values were found for individuals of two solitary species, Etheostoma caeruleum and Cottus cagnatus. Lowest values were found for Esox and Salmo gairdjleri. 3. Schooling in Perca paoescens, Lepomis macrochirus and Pimephales promelas significantly reduced fast-start response latencles by 7-16 msec. A 4 msec. reduction for Notropis cornutus was not significant. 4. No reduction in fast-start response latency was found for Pimephales promelas given the illusion of a school or for individuals greater than 15 cm from a school. 5. The observed variation in fast-start response latency would favour attack success of predators and escape success for schooled, but not solitary, presumptive prey. INTRODUCTION Variation in response latency could therefore have a Piscivorous behaviour of fish predators ranges from large effect on vulnerability of prey species. Furtherchasing to ambushing prey. The outcome of any intermore, social interactions, such as schooling could action between the predator and the prey fish depends affect the response, either by delaying fast-starts due on three factors; (a) relative performance (velocity, to the noise of other individuals, or reducing delay by acceleration rate): (b) manoeuvre (turning radius): (c) preparatory interactions. timing (delay in response to a protagonist’s The objective of this study was therefore to determanoeuvre); see Howland (1974), Webb (1976) and mine fast-start response latencies of a variety of freshElliott et al. (1977). The importance of performance water teleosts, such as predatory species, forage and manoeuvre parameters have been described by species, solitary fish and schools. Howland (1974) and Elliott et al. (1977). Webb (1976) evaluated the importance of timing in a theoretical MATERIALS AND METHODS treatment of acceleration attacks by piscivores. He concluded that the outcome of such an interaction Observations were made on eight species of teleosts would depend more on timing than performance or (Table 1). Esox. and Salvo gairdneri were obtained from manoeuvre. This was because response latencies were local fish hatcheries. Other species.were seined from local expected to be of the order of 15-25 msec which are ponds and streams. long compared to lunging attacks lasting Fish were held in 110 I. tanks, continuously flushed with 60-2OOmsec. (Dill, 1973: Hurley & Hartline. 1974). freshwater at 501. h-‘. Fish were acclimated to 15°C by increasing the water temperature from ambient to 15°C Table I. Total lengths ()7 + 2 SE) of species used to measure fast-start response laten. ties to a d.c. shock stimulus Species Length Notes Etheostoma caeruleum Storer (rainbow darter) Coccus huirdi (Grand) (molted sculpin) Salvo gairdneri Richardson (rainbow trout) $ Esox lucius L. Mitchill ,; E. masquinong) (tiger musky) Percu Jaoescens Mitchill (yellow perch) Lepomis macrochirus Rafinesque (bluegill) Notropis cornutus Mitchill (common shiver) Pimephales promelas Rafinesque (fathead minnow) 6.2 f 0.3