Predator avoidance in naive and experienced juvenile chinook and coho salmon

Abstract

We compared the vulnerability of naive and experienced coho and chinook salmon to predation by rainbow trout and related these findings to observations of the specific behaviour of each species during an encounter with the predator. Naive chinook were significantly less vulnerable to capture than naive coho in an open field encounter but there was no difference in capture rate of experienced coho and chinook. In videotaped encounters we found that coho and chinook behaved in significantly different ways when attacked by the predator, both when naive and when experienced. Our results suggest that predator avoidance strategies are highly species specific, that both species adjusted their behaviour after experience with the predator, and that the behavioural changes adopted by coho improved their ability to avoid the predator in an open field but those adopted by chinook did not. Considerable recent research has explored the willingness of different species, sexes, or life stages to risk exposure to a predator to obtain some reward (usually food). Our results further suggest that published experiments that purport to demonstrate differences in risk taking among types of prey may, instead, demonstrate differences in predator avoidance capability.

Repeated antipredator conditioning: a pathway to habituation or to better avoidance?

“…Following pilot tests with different predator individuals, it was decided to use as few predators as possible, in order to minimize the variance in the results that changes in predator behaviour among the trials would entail (Healey & Reinhardt, 1995). Furthermore, it became evident that the motivation of pikeperch to attack a prey once given a chance remained steady when they were companioned with another pikeperch.…”

Invasive predator tips the balance of symmetrical competition between native coral‐reef fishes

“…and defenses (Bateman and Fleming ), greater energetic costs associated with antipredator response (Martín and López ), and increased risk of capture by gape‐limited predators (Urban ). Smaller body size often also coincides with earlier life stages of prey that are typically more vulnerable to predation having had limited opportunities for learned recognition of predators (Healey and Reinhardt , Brown and Chivers , Lönnstedt et al. ).…”

Development of a Natural Rearing System to Improve Supplemental Fish Quality, 1996-1998 Progress Report.

“…When cutthroat odor was introduced two days later, smolts previously treated with conspecific extract spent more time motionless than those previously treated with swordtail extract. Healey and Reinhardt (1995) found a reduction in swimming activity was the primary response exhibited by chinook salmon fry to rainbow trout predators. Reduced swimming activity appears to be a general defense against predation for other juvenile salmonids (Lima and Dill 1990, Martel and Dill 1995, Brown and Smith 1997.…”

“…Predator avoidance differences in hatchery and wild juvenile steelhead (O. mykiss) have a genetic basis (Johnsson andAbrahams 1991, Berejikian 1995); however, within populations, the ability of hatchery-reared juvenile salmonids to avoid predation improves with experience. Laboratory studies have demonstrated that antipredator behavior and predator avoidance by juveniles of several salmon species increased after exposure to predators , Berejikian 1995, Healey and Reinhardt 1995, and this is the necessary stimulus to trigger innate antipredator responses (Suboski 1988, Olla and. However, in-culture predator training has had limited success improving survival of juvenile salmonids released into natural streams .…”