No abstract

Home range has been estimated for a limited number of marine fishes; however, the use of space and timing of activities within the home range has rarely been studied. In addition, understanding movement patterns of exploited fish species has been identified as a crucial science gap, impeding informed marine reserve design. We used a radio-acoustic positioning telemetry (VRAP) system to monitor detailed movements of 10 blue rockfish Sebastes mystinus around shallow rock pinnacles and stands of bull kelp Nereocystis leutkeana in central California in September 2002. The mean home range was 8783 m 2 ± 1137 SE; however, activity was highly concentrated in 1 to 3 core areas within each home range. Mean core areas measured 1350 m 2 ± 286 SE, but accounted for ~83% of activity. All core areas were centered over rock pinnacles where rockfish were highly aggregated. Individuals exhibited high site fidelity and made only brief radial excursions away from these centers or moved directly from one pinnacle to the next along defined corridors. Patterns of diel activity and nocturnal sheltering corresponded closely with nautical twilight. Cores overlapped, but estimated locations of nocturnal shelters differed significantly among individuals. Movement patterns were correlated with wind velocity, upwelling index, water temperature and habitat structure. KEY WORDS: Sebastes mystinus · Rockfish · Movement · Home range · Tagging · Core areas Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 327: [157][158][159][160][161][162][163][164][165][166][167][168][169][170] 2006 among terrestrial animals has been attributed to patterns of refuging (e.g. Hamilton & Watt 1970) and foraging (Samuel et al. 1985, Kenward et al. 2001. Patterns of core area use in marine fishes are also likely to have important implications for understanding the ecological determinants of space use; however, very little is known other than that core areas are increasingly detected as tracking technologies improve. Holland et al. (1993) identified core areas within which juvenile hammerhead sharks Sphyrna lewini restricted their diurnal movements to a small portion of their total home range (a turbid portion of an island bay), suggesting an anti-predation function. In the oceanic environment, adult S. lewini aggregate at oceanic seamounts during the day, and from these refuging cores make nocturnal foraging movements into a much broader pelagic environment (Klimley & Nelson 1984). Parsons et al. (2003) identified core areas for 4 individual snapper Pargus auratus that were relatively stable over a period of 4 lunar cycles, while a fifth individual gradually changed the number and location of occupied cores. The location and timing of core area use was not, however, attributed to particular activities or habitat resources. While the quality of habitat is likely to influence the extent (Mathews 1990, Lowe et al. 2003 and the shape (e.g. Holland et al. 1996, Topping et al. 2005) of the home range, the extent ...

No abstract

A hammerhead shark Sphyrna lewini tracked for 74 days revealed an expansion of the range of vertical distribution for the species to include the extreme hypoxic environment of the oxygen minimum layer in the Gulf of California.

No abstract

No abstract

Water temperature plays a critical role in mediating energy budgets and influencing the behavior of marine ectotherms. Previous research has demonstrated that marine ectotherms such as sea turtles conserve energy by decreasing activity levels in colder water—often at or near the latitudinal limits of their range. San Diego Bay is near the northern edge of the range for eastern Pacific green turtles and is home to a year-round foraging population. Turtles in San Diego Bay experienced a significant decrease in ambient water temperature following the closure of a fossil-fuel-based power plant and corresponding loss of the plant’s warm-water effluent. Time-depth recorders were placed on 13 turtles before (n = 5) and after (n = 8) the closure of this plant to determine how changing water temperature influenced dive duration. Deployments lasted 2-25 d, with a mean deployment of 7.5 d. Green turtle behavior in different thermal regimes revealed a strong relationship between dive duration and water temperature; dive duration was significantly longer when water temperatures were colder, especially when water was below 14.4°C. Establishing the inactivity threshold for this population is critical to future management in light of temperature variability in coastal habitats and the impacts this may have on sea turtle energetics. Understanding organismal response to relatively rapid shifts in thermal conditions is relevant to assessments of the direct and indirect anthropogenic effects on aquatic environments.