In organisms that have a life history phase whose dispersal is influenced by abiotic forcing, if individuals of different species are simultaneously exposed to the same forcing, spatially correlated settlement patterns may result. Such correlated recruitment patterns may affect population and community dynamics. The extent to which settlement or recruitment is spatially correlated among species, however, is not well known. We evaluated this phenomenon among 8 common kelp forest fishes at 8 large reefs spread over 30 km of the coast of Santa Catalina Island, California. In addition to testing for correlated recruitment, we also evaluated the influences of predation and habitat quality on spatial patterns of recruitment. Fish and habitat attributes were surveyed along transects 7 times during 2008. Using these repeated surveys, we also estimated the mortality rate of the prey species that settled most consistently (Oxyjulis californica) and evaluated if mortality was related to recruit density, predator density, or habitat attributes. Spatial patterns of recruitment of the 8 study species were seldom correlated. Recruitment of all species was related to one or more attributes of the habitat, with giant kelp abundance being the most widespread predictor of recruitment. Mortality of O. californica recruits was density-dependent and declined with increasing canopy cover of giant kelp, but was unrelated to predator density. Our results indicate that physical forcing of larval delivery did not generate spatially correlated patterns of recruitment in a suite of temperate-reef fishes.
As part of a 7‐year lifecycle monitoring study, electroshocking was used to capture and characterize a small population of federally listed endangered southern California steelhead Oncorhynchus mykiss in Topanga Creek, Los Angeles, California. Electroshocking is a tool widely used to study fish populations, despite its potential behavioral and physical effects on individuals. We examined rates of external hemorrhaging (i.e., branding) and its effect on growth rates and survival of recaptured individuals. Rates of branding were low (0–3%) during most November events from 2008 to 2014, but higher during all March events (8–23%) and during the November 2011 event (13%). Overall, 5% of the total captured individuals exhibited branding. Growth rates (mm/d) of individuals recaptured after branding were not significantly different, but on average were 9% lower than average daily growth rates for individuals in the same size‐class captured and recaptured in the same time periods. In general, larger fish were more likely to be branded than were smaller fish (P < 0.0001). Although 69% of brandings occurred in pool habitats, which tend to be larger and deeper than other habitats, branding was not significantly more likely to occur in any habitat type (P = 0.13) or in any substrate type (P = 0.16), and mean or maximum depth of habitat was not related to the rate of branding. The population‐level effects associated with branding remain unclear. Although important information has been obtained through the use of electroshocking, the cumulative effects of electroshocking‐induced injuries to this endangered species need to be considered.
Received March 2, 2015; accepted March 27, 2016 Published online July 19, 2016
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