Substrate-related differences in anti-predator behaviour of two gobiid fish species and the brown shrimp, and their adaptive value

Abstract

Factors affecting the predator-related mortality of sand goby Pomatoschistus minutus (Pallas), common goby P. rnicrops (Kreyer) and brown shrimp Crangon crangon L. were investigated in Gullmar Fjord, Sweden. Substrate selection and locomotory activity was recorded in the 3 species on sand and on mud. Sand goby and brown shrimp preferred sand to mud, while common goby preferred mud to sand. Activity was clearly correlated to substrate type. In all 3 species, swimming activity was increased by a factor 4 when kept on the less preferred substrate. Predation experiments were performed with sand or mud as bottom substrate and with cod as predator. On sand, common gobies were more rapidly eliminated by the predator than were sand gobies, and sand gobies more rapidly than brown shrimps. On mud, sand gobies were more rapidly taken than were common gobies and brown shrimps. Staying on the 'wrong' substrate will result in increased locomotory activity which will in turn increase the risk of predation. We suggest that the microgeographical distribution of members of the epibenthic guild is primarily a consequence of various behaviour patterns. Predators act to restrict the habitat use of these fish and shrimp species. Differences in behaviour between the species when encountering a predator reduce their vulnerability to predators on their respective preferred substrate. This may in part explain the spatial segregation and will contribute to the maintainance of community structure.

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

“…Sale 1991) systems over a wide range of latitudes (Heck & Wilson 1987 Gotceitas & Brown 1993, Gotceitas et al 1995, Gregory & Anderson 1997, Lindholm et al 1999). Structurally complex habitats impair the visual and swimming capabilities of predators (Savino & Stein 1982), which in turn can reduce the effectiveness of encountering, attacking and capturing prey (Tallmark & Evans 1986). Our results were consistent with these findings.…”

Abundance and spatial overlap of gobies (Gobiidae) in Lough Hyne, Ireland

“…Under experimental conditions, Tallmark & Evans (1986) found greater predation of gobies on their less preferred substrata. Vaas et al (1975) recorded Pomatoschistus minufus and P. microps (Kroyer) in the diet of G. niger in Dutch waters.…”

Behavioural consequences of density-dependent habitat use in juvenile cod Gadus morhua and G. ogac: the role of movement and aggregation

“…However, under certain conditions, habitat-specific behaviour can lead to increased mortality. For example, gobies increase their activity levels in open habitats, which ultimately leads to increased predation rates (Tallmark & Evans 1986). It is therefore difficult to speculate on the advantage of juvenile cod shoaling in sand in years of high abundance since we did not measure the fitness consequences of such behaviour.…”