Size-related changes in vulnerability to predators and spatial refuge use by juvenile Iceland scallops Chlamys islandica

Abstract

ABSTRACT. We examined size-related changes in vulnerability of juvenile Iceland scallops Chlamys islandica to crab and asteroid predators using field experiments in the Mingan Islands, northern Gulf of St. Lawrence, eastern Canada. Vulnerability to both crabs and asteroids markedly decreased with scallop size, likely because of increases in the effectiveness of the scallop's antipredator defenses. Multiple-choice experiments showed that the crabs Hyas araneus and Cancer irroratus preyed mainly upon small scallops (10 to 30 mm). At our study site H. araneus was the most abundant decapod and was likely the major predator of scallops. Small Iceland scallops were generally found in crevices, byssally attached to the undersides of dead shells and rocks. Use of these refuges did not show die1 periodicity but decreased markedly with scallop size, attaining 0% for >60 mm scallops. Tethering experiments indicated that refuge use decreased vulnerability to both crabs and asteroids. However, the advantage of refuge use, in terms of reduced predation risk, varied with scallop size, being maximal for 15 to 30 mm scallops and only marginal for larger, less vulnerable scallops.

Predator distribution and habitat patch area determine predation rates on Age-0 juvenile cod Gadus spp.

“…Tethering studies are numerous, including a wide variety of marine and freshwater organism such as decapod crustacea (Heck & Wilson 1987, Eggleston et al 1990, Wilson et al 1990), bivalves (e.g. Arsenault & Himmelman 1996), freshwater fish (Gregory & Levings 1998, Post et al 1998) and marine fish (Curran & Able 1998, Linehan et al 2001. The technique has its detractors (e.g.…”

Invariant size–frequency distributions along a latitudinal gradient in marine bivalves

“…14-17 and 30, but see refs. 31 and 32), vary strongly with latitude along the northeastern Pacific margin (33); (ii) the style and intensity of predation evidently change significantly with latitude (34)(35)(36), and size can be an important refuge from predation in marine benthos in general and mollusks in particular (34,35,(37)(38)(39)(40)(41); (iii) although adjacent provinces share species, almost complete taxonomic turnover occurs between the Arctic and Panamic Provinces with only four species ranging throughout; (iv) the family-level composition of the modal size class varies considerably with latitude ( Fig. 3), indicating further that these patterns also are not shaped by higher-level phylogenetic effects such as the presence of a few species-rich, cosmopolitan families; and (v) at least some provincial boundaries are size-selective such that SFDs of the species that cross a given boundary differ significantly from those that stop at that boundary.…”

Use of refuges by the ophiuroid Ophiopholis aculeata: contrasting effects of substratum complexity on predation risk from two predators

“…Structural components can either make the prey less visible (Main 1987) or enhance escape by slowing the movement of predators (Ryer 1988, Bartholomew et al 2000 and permitting prey to stay out of their reach (Main 1987). The use of refuges is a good means of avoiding fast-moving, visual predators and can also reduce predation by slow-moving predators that locate prey using chemodetection (Levitan & Genovese 1989, Arsenault & Himmelman 1996, Wong & Barbeau 2003. As a general rule, habitat complexity reduces predation but systems with ambush predators are an exception; in these cases habitat complexity may not affect, or may even increase, mortality from predation, as structural components reduce the capacity of prey to detect predators (James & Heck 1994, Walsh 1995, Flynn & Ritz 1999.…”