Data Set (knb-lter-sbc.97.1)

Data to support "Stochastic density effects on adult fish survival and implications for population fluctuations"

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These methods, instrumentation and/or protocols apply to all data in this dataset:

Protocols and/or Procedures
Description:

Methods

Data on stage-specific abundance of black surfperch, the amount of foraging habitat and the availability of their food were collected at 11 fixed locations within 4 sites on the north shore of Santa Cruz Island, CA in autumn annually from 1993-2009. At each location, fixed 40x2m transects at 3, 6, and 9 m depth contours (the typical black surfperch depth range) were surveyed for black surfperch and their foraging habitat by divers using SCUBA, and samples were collected to estimate their principal crustacean food items. Counts of fish distinguished among young-of-year, juveniles (1 year old) and adults (>= 2 years old).

We defined foraging habitat as the average annual percent cover of all low-lying turf and foliose algae from which black surfperch harvest prey (Laur and Ebeling 1983, Holbrook and Schmitt 1984, Schmitt and Holbrook 1984) across all transects within each site. Food density was defined as the observed biomass density of prey (g wet mass m^-2), which included jaeropsid and idoteid isopods, gammarid and caprellid amphipods and crabs within the adult black surfperch gape limitation (Schmitt 1984).

Estimates of food density for each site were calculated as in Okamoto et al. (2012) and include the density of prey sampled from replicate 0.1 m^2 patches of foraging habitat in each year from which individual prey were counted and sized. Food biomass was not normalized by the habitat percent cover on transects (as was done in Okamoto et al., 2012) so habitat and biomass density of food could be evaluated independently. Annual means of the biomass density of food averaged over all sites for each year of the time series were used as values for food availability in all analyses.

Fish and habitat time series in this dataset are annual site means while prey time series are annual means across all sites.

References

Holbrook, S.J. and Schmitt, R.J. (1984). Experimental analyses of patch selection by foraging black surfperch (Embiotoca jacksoni Agazzi). Journal of Experimental Marine Biology and Ecology, 79, 39-64.

Laur, D.R. and Ebeling, A.W. (1983). Predator-prey relationships in surfperches. Environmental Biology of Fishes, 8, 217-229.

Okamoto, D.K., Schmitt, R.J., Holbrook, S.J. and Reed, D.C. (2012). Fluctuations in food supply drive recruitment variation in a marine fish. Proceedings of the Royal Society B: Biological Sciences, 279, 4542-4550.

Schmitt, R.J. and Holbrook, S.J. (1984). Gape-limitation, foraging tactics and prey size selectivity of two microcarnivorous species of fish. Oecologia, 63, 6-12.