Copyright (c) 2013 Occidental College All rights reserved. http://scholar.oxy.edu/vrg Recent documents in Vantuna Research Group en-us Thu, 21 Mar 2013 16:00:24 PDT 3600 http://scholar.oxy.edu/vrg/7 http://scholar.oxy.edu/vrg/7 Thu, 29 Mar 2012 17:14:57 PDT Spotfin croakers Roncador stearnsii, a prized recreational catch, were collected throughout the Southern California Bight, primarily as bycatch from a long-term, scientific gill-net collection effort. The maximum otolith-based age in the present study was 24 years—14 years greater than in a previous scale-based aging study. Multiple models were used to estimate mean length at age, including models that utilize larvae as well as juveniles and adults, and the model selection results suggest sexual dimorphism in growth patterns. The juvenile and adult catch per unit effort reflected a clear pattern of habitat selectivity, with fish strongly preferring soft-bottom habitats. Catches in rocky-reef areas were limited but tended to increase with water temperature. The data also suggest that spotfin croakers segregate themselves sexually during the spawning season, when recreational fishing from jetties will target males and fish caught in bays and estuaries are more likely to be spawning females. These results provide further evidence for the importance of protection and restoration efforts for estuaries and bays along this well-developed coastline. The growth of larvae captured in plankton tows in July and September 2004 was substantially faster than that of larvae sampled in May, which coincided with warmer sea surface temperatures, highlighting a potentially important relationship relating temperature (and therefore geography) and settlement success.

]]> Jonathan P. Williams et al. http://scholar.oxy.edu/vrg/6 http://scholar.oxy.edu/vrg/6 Thu, 29 Mar 2012 17:02:04 PDT On 22 October 2006, a Pacific sierra (Scomberomorus sierra) was caught by gillnet near Mother’s Beach, Marina del Rey, Los Angeles County, California (33º58’50"N, 118º27’25"W) during sampling for juvenile white seabass (Atractoscion nobilis). This catch represents the northernmost record of Pacific sierra, and one of several specimens known from California.

]]> Jonathan P. Williams et al. http://scholar.oxy.edu/vrg/5 http://scholar.oxy.edu/vrg/5 Thu, 29 Mar 2012 16:57:38 PDT Studies of the impact of El Niño periods on marine species have usually focused on negative, highly visible eVects, e.g., decreasing growth rates or increasing mortality due to a decline in primary productivity in typically nutrient rich upwelling zones; but positive effects related to elevated water temperature are also known. This study examined how the growth rate of juvenile white seabass, Atractoscion nobilis, responded to changes in ocean temperature in an El Niño period (1997–1998) in the northern portion of the Southern California Bight, USA. Growth rates of juvenile white seabass during their first 4 years of life were estimated as the slopes of linear relationships between body mass and age (from otoliths) of 800 fish collected at 11 stations throughout the bight. Growth rates differed significantly among cohorts hatched in 1996–2001. Specifically, white seabass that hatched in 1996 and 1997 grew significantly faster than those that hatched in 1998, 1999, and 2001. These differences in growth rates of cohorts appeared to be driven by variation in sea-surface temperature (SST). Growth rates averaged over the first three or 4 years of life were signiWcantly positively corre- lated to average daily SST during the first 1–4 years of life. Increased growth of juvenile white seabass during the warm El Niño period likely provided a number of benefits to this warm-temperate species. This study demonstrated that some species will benefit from these warm-water periods despite reduced system-wide primary production.

]]> Jonathan P. Williams et al. http://scholar.oxy.edu/vrg/4 http://scholar.oxy.edu/vrg/4 Thu, 29 Mar 2012 16:48:39 PDT Queenfish Seriphus politus were collected at coastal power plants from San Clemente to Ventura, California. Power functions best described relations between otolith length, width, or weight and either standard length (SL) or total body weight. The length–weight relationship was described by the following equation: weight 1⁄4 10􏰀5 3 SL3.09. Individuals were aged to 12 years by using sagittal otolith sections. Females grew at a significantly faster rate than males. Both sexes reached 50% maturity by 100 mm SL, or shortly after age 1. The total annual instantaneous mortality coefficient was estimated at 0.42. Catalina Harbor (on the windward side of Santa Catalina Island) and Ventura were the most populous sites based on gill-net catch per unit effort from 1995 to 2006. Juvenile and adult queenfish populations have declined since 1980 in a significant relationship with nearshore plankton biomass. Larval queenfish densities recorded in King Harbor (Redondo Beach) have declined since 1987. Long-term recruitment estimates indicated peak recruitment prior to 1976, with three subsequent downward baseline shifts.

]]> Eric Miller et al. http://scholar.oxy.edu/vrg/3 http://scholar.oxy.edu/vrg/3 Thu, 29 Mar 2012 16:48:38 PDT Larval Genyonemus lineatus and Seriphus politus collected using bongo frames fitted with 0.333 mm mesh nets between December 2003 and September 2004 off Huntington Beach, California, were examined to characterize their daily growth patterns. Samples from one net were fixed in a 4% buffered formalin-seawater solution while those from the other net were preserved in 70% ethanol. All formalin-fixed samples were transferred to 70% ethanol ~72 hours after collection. Growth was best described by a linear equation for G. lineatus (L = –0.833 + 0.242A; R2 = 0.84) and a power function for S. politus (L = 0.825 × A0.647; R2 = 0.76). Sufficient S. politus were available to analyze seasonal effects on growth rate; no significant differences were detected. No significant difference in the S. politus growth rate between preservation media was detected for samples collected on September 1, 2004.

]]> Eric Miller et al. http://scholar.oxy.edu/vrg/2 http://scholar.oxy.edu/vrg/2 Thu, 29 Mar 2012 16:12:11 PDT Kelp Bass (Paralabrax clathratus) and California Sheephead (Semicossyphus pulcher) are economically and ecologically valuable rocky reef fishes in southern California, making them likely indicator species for evaluating resource management actions. Multiple spatial datasets, aerial and satellite photography, underwater observations and expert judgment were used to produce a comprehensive map of nearshore natural rocky reef habitat for the Santa Monica Bay region (California, USA). It was then used to examine the relative contribution of individual reefs to a regional estimate of abundance and reproductive potential of the focal species. For the reefs surveyed for fishes (i.e. 18 out of the 22 in the region, comprising 82% the natural rocky reef habitat ,30 m depth, with a total area of 1850 ha), total abundance and annual egg production of California Sheephead were 451 thousand fish (95% CI: 369 to 533 thousand) and 203 billion eggs (95% CI: 135 to 272 billion). For Kelp Bass, estimates were 805 thousand fish (95% CI: 669 to 941thousand) and 512 billion eggs (95% CI: 414 to 610 billion). Size structure and reef area were key factors in reef-specific contributions to the regional egg production. The size structures of both species illustrated impacts from fishing, and results demonstrate the potential that relatively small increases in the proportion of large females on larger reefs could have on regional egg production. For California Sheephead, a substantial proportion of the regional egg production estimate (.30%) was produced from a relatively small proportion of the regional reef area (c. 10%). Natural nearshore rocky reefs make up only 11% of the area in the newly designated MPAs in this region, but results provide some optimism that regional fisheries could benefit through an increase in overall reproductive output, if adequate increases in size structure of targeted species are realized.

]]> Jeremy T. Claisse et al. http://scholar.oxy.edu/vrg/1 http://scholar.oxy.edu/vrg/1 Wed, 10 Nov 2010 15:00:54 PST In 2008, the California Department of Fish and Game (DFG) began a one-year process to develop a preferred alternative for a network of marine protected areas in Southern California. To comply with the state Marine Life Protection Act’s mandate for sound science, the DFG appointed marine scientists to a Science Advisory Team to set up guidelines that stakeholders and decision makers could rely upon to determine how well proposals met the goals of the MLPA to provide some protection for marine life. As the final debates over where to draw the lines of the new reserves continue, this article explains the scientific underpinnings of this groundbreaking process.

]]> Daniel J. Pondella