Geographic variation in density, demography, and life history traits of a harvested, sex-changing, temperate reef fish

Abstract

Geographic variation in ecological and environmental factors may lead to intraspecific differences among populations. For the California sheephead ( Semicossyphus pulcher ), an important predator in kelp forests and a target of commercial and recreational fisheries, we evaluated the degree to which different populations exhibited variation in density, demography, and life history traits. We assessed biogeographic patterns of abundance through underwater visual census at 39 sites spanning a major portion of the species range (southern California, USA, to Baja California, Mexico) and made collections from seven focal sites to investigate geographic differences in demography and life histories. California sheephead densities were significantly greater in the southern part of their range and at offshore islands than along the mainland coast. At the focal sites, we found significant spatial variation in density, fecundity, size structure, growth rates, annual survivorship, and the timing of maturation and sex change. Density- and temperature-dependent effects helped to explain the intraspecific differences in these parameters. Studies such as this one will allow for demographic plasticity to be incorporated into future stock assessments. Management of temperate reef fishes may best be achieved on smaller spatial scales as we increase our understanding of geographic variation among populations.

Otolithometry and scalimetry—two valid methods to describe the growth of peacock wrasse, Symphodus tinca (Actinopterygii: Perciformes: Labridae) from eastern Algeria

“…The latter value is lower than that reported by Pallaoro and Jardas (2003) (42.5 cm), Quignard and Pras (1986) (35 cm), and Tortonese (1975) (35 cm) in middle eastern Adriatic, southern of France and Italy coasts, respectively, but higher than the values recorded by Dieuzeide et al (1955) (30 cm) and Svetovidov (1964) (30 cm) in Algerian coasts and Black Sea, respectively. These differences could be due to a biogeographic difference in growth rate (Caselle et al 2011), but also to differences in local fishing pressure (Weijerman et al 2013).…”

Demographic patterns in the peacock grouper (Cephalopholis argus), an introduced Hawaiian reef fish

“…Selective fishing practices influence demography and life history strategies, as demonstrated in several species of marine fishes (Rijnsdorp & Vanleeuwen 1992, Buxton 1993, Choat et al 2003, Williams et al 2003, Berkeley et al 2004, Hamilton et al 2007, Taylor & McIlwain 2010, Caselle 2011. Differences in growth of the parrotfish Sparisoma viride in the tropical Atlantic were found to vary with fishing pressure (Choat et al 2003).…”

“…A range of factors related to variation in demography of both temperate and tropical fishes have been investigated including environmental conditions (Robertson et al 2005a, Ruttenberg et al 2005, Trip et al 2008, ecological processes (Gust et al 2002, Williams et al 2003, Pears 2005, and anthropogenic impacts such as fishing (Trip et al 2008, Taylor & McIlwain 2010, Caselle 2011. Together, these observations indicate that coral reef fishes exist as spatial populations with geographically varying phenotypic traits.…”

Spatial and temporal comparisons of gopher rockfish (Sebastes carnatus) life history and condition in south central California

“…Naturally occurring environmental factors may influence life history traits in fishes (Reznick et al 1990;Ruttenberg et al 2005;Hamilton et al 2007;Caselle et al 2011). Furthermore, anthropogenic factors like fishing (Rijnsdorp 1993;Rochet 1998;Law 2000;Conover 2007) can also alter these characteristics.…”

“…Life history traits including growth parameters and maturity calculations are critical to determine appropriate fisheries management efforts; they can be used as indicators to predict species and population-level vulnerability (Adams 1980;Roff 1984;Stokes et al 1993;Reynolds et al 2005), and to determine localized management strategies (Caselle et al 2011) in the form of harvest restrictions for economically valuable species. Allowable harvest rates should be calculated based on life history data from local populations so that Biological…”