Effects of habitat on settlement, growth, and postsettlement survival of Atlantic cod (Gadus morhua)

Abstract

Settlement and growth of age 0+ cod were monitored using snorkel and self-contained underwater breathing apparatus (SCUBA) in four distinct habitat types (sand, seagrass, cobble, and rock reef) in St. Margaret's Bay, Nova Scotia. Newly settled cod were marked with acrylic dye, allowing repeated visual length estimates of individual fish. Settlement of cod did not differ between habitat types, but postsettlement survival and subsequent juvenile densities were higher in more structurally complex habitats. These differences appear to be due to increased shelter availability and decreased predator efficiency in structurally complex habitats. Growth rate was highest in seagrass beds, while the efficiency of cod predators was lowest and cod survival was highest on rocky reefs and cobble bottoms. Thus, trade-offs occur between energy gain and predation risk. In St. Margaret's Bay, the population structure of Atlantic cod may be less influenced by patterns of larval supply than by postsettlement processes such as habitat-specific growth and mortality.

Ontogenetic patterns of habitat use by reef-fish in a Marine Protected Area network: a multi-scaled remote sensing and in situ approach

“…The availability and quality of reef habitat, in turn, can affect the post-settlement demography of reef-fish directly by providing refuge from predation (Hixon & Beets 1993) or indirectly by modifying biological interactions among different species (Menge et al 1985, Hixon & Mark 1997. Hence, the abundance and distribution of many life history stages of reef-fish can best be explained by identifying and quantifying the abundance and distribution of habitats necessary for successful recruitment, growth and reproduction (Doherty & Williams 1988, Tupper & Boutilier 1995, Friedlander & Parrish 1998.…”

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

“…Despite their preference for eelgrass, however, juvenile cod are occasionally observed over less-structured habitats such as sand and cobble (Lough et al 1989, Tupper & Boutlier 1995a,b, Laurel et al 2003a). Juvenile cod are believed to move little immediately following settlement (Tupper & Boutilier 1995a,b, Grant & Brown 1998a, and, consequently, the occupation of less-structured habitats is taken to be the result of indiscriminate settlement patterns. By implication, temporal variation in distribution following settlement is the result of selective predation across habitats (Tupper & Boutilier 1995a,b).…”

Importance of bioturbators for biodiversity maintenance: indirect effects of fishing disturbance

“…On mixed substrata, the passage of a trawl can destroy structural species such as anemones, bryozoans and sponges and, in doing so, degrade the spatial complexity of the habitat (Tupper & Boutilier 1995). This in turn has been shown to reduce the survivorship of juvenile commercial fish species (Tupper & Boutilier 1995).…”

“…This in turn has been shown to reduce the survivorship of juvenile commercial fish species (Tupper & Boutilier 1995). The presence of epifaunal, structural species in mixed substrata is visually apparent, making it easy to appreciate the increased complexity that such species add to the habitat.…”