Juvenile movement patterns in a territorial scorpaenid fish before and during settlement

Abstract

The gopher rockfish Sebastes carnatus is a territorial resident of the kelp forests of central California. Dunng summer, young-of-the-year recruit initially to the kelp canopy where they stay for about 1 to 2 mo prior to joining conspecific adults on the bottom. Movement patterns of these juveniles were studied in the kelp canopy The juveniles tended to b e site-attached in the kelp canopy even though there is no apparent advantage in this behavior in the canopy microhabitat. They also appear to explore new areas prior to shifting habitat. These and previous results suggest that there are fundamental behavioral similarities between pre-settlement juveniles and adults of the same species despite dramatic ecological changes due to growth and change of habitat.Many organisms undergo dramatic changes in habitat and ecology as they pass from one life stage to another. This is particularly evident for marine organisms with planktonic larvae and demersal adults. The behavior of these organisms generally changes between stages in ways that seem to suit new conditions. However, the proximate causes of behavioral change between life history stages are not well understood. This is a particularly difficult topic to address because genetically-programmed changes in behavior, corresponding to the physical changes that can occur during metamorphosis, are difficult to differentiate from environmentally-induced behavioral modification. Optimally, the behavior of an individual would be modified to accomodate changes in habitat or the morphology of the individual. The purpose of this study was to reveal fundamental changes or consistencies in the behavior of juvenile gopher rockfish Sebastes carnatus as they settle from a pelagic existence to the substrate of the rocky reef where they become territorial.The gopher rockfish is a viviparous species whose offspring are released into the plankton in early spring (Larson 1980a). The young return to kelp forests along the central California coast, USA, when they have reached ca 30 mm standard length (Hoelzer 1987). This event will be termed 'recruitment' in this paper. The @ Inter-Research/Printed in F R. Germany giant kelp Macrocystis pyrifera forms a dense surface canopy during summer. The juvenile rockfish are cryptically colored in the canopy microhabitat where they remain for 1 to 2 mo (Carr 1983, pers. obs.). Eventually they move to the rocky substrate where they reside for the rest of their lives. This event will be called 'settlement'. They feed on suspended zooplankton until they settle to the bottom, at which time they begin to take demersal crustaceans such as shrimps and amphipods (Singer 1985, pers. obs.).Two fundamental aspects of territorial behavior in this species are site-specificity and aggressive defence of resources (Hallacher 1977, Larson 1980a. These behaviors have not been observed in the juveniles prior to settlement. Hoelzer (1987) demonstrated that juveniles collected from the kelp canopy behave aggressively toward their images in a mirror. Indeed, t...

Nearshore seascape connectivity enhances seagrass meadow nursery function

“…c, triangles). As rockfish have high site‐fidelity during early life stages (Hoelzer , Nelson ), we assumed biological site independence by maintaining a minimum distance of 100 m between meadow sites during site‐selection. For additional habitat comparisons of recruitment, sites were also established within the N. luetkeana kelp forests ( n = 4) and sand habitats ( n = 4), directly adjacent to the seagrass edge sites (Fig.…”

Microhabitat requirements for settlement of juvenile sparid fishes on Mediterranean rocky shores

“…Habitat selection by fishes during recruitment is a widely documented phenomenon in tropical coral reefs (Williams & Sale, 1981 ;Sale et al, 1984 ;Shulman, 1985 ;Jones, 1988 ;Doherty, 1991) . In temperate regions, most information comes from giant kelp forests (Hoelzer, 1988 ;Carr, 1989 ;, rocky reefs (Smale & Buxton, 1989 ;Lincoln Smith et al, 1991) and soft bottoms (Riley et al, 1981 ;Labourg et al, 1985 ;JugDujakovic, 1988 ;Warburton & Blaber, 1992) . Nevertheless, little information is available on the choice of habitat at settlement of most littoral fish species in the Mediterranean .…”

Structural complexity in relation to the habitat preferences, territoriality, and hatchery rearing of juvenile China rockfish (Sebastes nebulosus)

“…We tested whether juveniles can also show territorial behavior; these data would enable the prediction of how they establish spatial relationships with each other in nature (Brown and Orians 1970). See Hoelzer (1987;1988) for observations of early aggression and site fidelity in two other rockfish species. Understanding mechanisms of competition enables the prediction of which individuals will have an advantage in obtaining resources (e.g., Brown et al 2005;Nakano 1995).…”