Significance of body size to the interaction between a larval fish {Mallolus villosus) and a vertebrate predator (Gasterosteus aculeatus)

Abstract

ABSTRACT. We investigated the influence of variations in the size of prey (Mallotus villosus) and a vertebrate predator (Gasterosteus aculeatus) on larval fish mortality rates during the period of yolk absorption using mid-size mesocosms (2.7 m". Increasing predator size increased mortality rates of capelin larvae. Variations in larval capelin size resulted in 2 distinct patterns. Between experimental trials, greater mean size of larval capelin in the mesocosm reduced mortality due to predation. Within an experimental mesocosm, larger larvae suffered higher mortality than smaller individuals. Contrasting patterns of size-dependent vulnerability to predation reflect the hierarchy of processes that determine the probability that a larval fish will be preyed upon. The broad scale response of the predator was determined by the mean relative sizes of prey and predator which govern the average probabilities of encounter, attack and capture. Within the search ambit of a predator (e.g area or volume searched within a complete diurnal foraging cycle) active prey selection for larger prey due to either greater visibility or higher energy reward was an important factor. A comparison of our results with estimated predation rates by the jellyfish Aurelia aurita indicates that at a similar size a gelatinous zooplankter consumes fewer larvae than a stickleback and is a less efficient predator as measured by the energy ingested relative to energy demands. For both vertebrate and invertebrate predators, the ratio of prey to predator lengths was a strong predictor of the daily mortality rate due to predation. Relative prey-predator sizes may provide a useful perspective to assess changes in larval fish vulnerability as they grow through a predator field. INTRODUCTIONCumulative survival during the early life history of fish is influenced by both growth and mortality rates (Houde 1987, Beyer 1989, Pepin 1991 1982, Christensen 1983, Alheit 1986, Folkvord & Hunter 1986, Pepin et al. 1987, Fuiman & Gamble 1988, Fuiman 1989 predators can feed heavily on the early life history stages of fish. Second, predation rates on fish larvae by invertebrate carnivores tend to decrease as larvae increase in size (Theilacker & Lasker 1974, Bailey 1984, Bailey & Batty 1984, Purcell et al. 1987) whereas the predation rates on fish larvae by vertebrate predators first increase as larvae increase in size (Folkvord & Hunter 1986, Pepin et al. 1987, Fuiman 1989, Fuiman & Gamble 1989) but eventually decrease as the larvae become more capable of avoiding attacks (Fuiman 1989). The pattern of vulnerability of larval fish to different predator types is O Inter-Research/Printed in Germany

Three synergistic growth-related mechanisms in the short-term survival of larval Japanese anchovy Engraulis japonicus in Sagami Bay

“…This showed that the cumulative size-selective mortality was positively directed such that smaller individuals were more likely to survive. The higher probabilities of mortality among larger individuals have already been reported (Fuiman 1989, Litvak & Leggett 1992, Pepin et al 1992. There are various reasons for positive size-selective mortality.…”

Larval performance in an estuarine crab, Chasmagnathus granulata, is a consequence of both larval and embryonic experience

“…Smaller larvae (in terms of biomass) hatched from smaller eggs (Giménez & Anger 2001), and these showed a lower survival and longer duration of development not only under ad libitum feeding conditions (present study) but also when they were exposed to periods of starvation (Giménez 2002). Under weak osmotic stress, high initial biomass at hatching was associated with high levels of reserves in advanced zoeal stages , most likely as a consequence of an enhanced ability of larger zoeae to capture and ingest prey (Pepin et al 1992).…”

Risk of predation to fish larvae in the presence of alternative prey: effects of prey size and number

“…Although both invertebrate and vertebrate predators are known to include fish larvae in their diet, vertebrate predators such as planktivorous fishes have been shown to have the greatest impact on larval fish mortality (Fuiman & Gamble 1988, Litvak & Leggett 1992, Pepin et al 1992. As has been demonstrated for zooplankton, predation risk to fish larvae appears to be influenced by both body size (Litvak & Leggett 1992, Pepin et al 1992) and the presence of alternative prey (Bailey & Yen 1983, Pepin 1987). For example, several studies have found that the presence of alternative prey (i.e.…”

“…Cod larvae were reared in ambient seawater from eggs collected from a laboratory broodstock. All larvae used in experiments were 5 to 7 d post-hatch and similar in size (mean length f 1 SE = 4.4 f 0.13 mm), to eliminate effects due to larval age and size on risk to predation (Litvak & Leggett 1992, Pepin et al 1992.…”