Distribution of demersal fishes along the US west coast (Canada to Mexico) in relation to spatial fishing closures (2003-2011)

Abstract

A temporally and spatially variable Rockfish Conservation Area (RCA) was established as a marine protected area along the US west coast in 2002 to protect stocks of rockfishes Sebastes spp. Since the RCA falls within the region sampled annually by the West Coast Groundfish Bottom Trawl Survey, we utilized data collected from 2003 to 2011 to evaluate whether establishment of the RCA influenced catch per unit effort (CPUE), species richness, and size distribution of demersal fishes. We compared CPUE and species richness among 3 management areas (continuously closed, periodically closed, and open to commercial bottom trawling) using analysis of covariance models that account for variability due to area, year, and depth. The most appropriate models for CPUE (35 species treated individually and aggregated into 6 subgroups) and species richness were selected using Akaike's information criterion. All of the best-fit models were highly significant (p < 0.0001), explaining 3 to 76% of the variation in catch. For 27 species and 5 subgroups, mean CPUE was significantly greater within the area continuously closed to commercial bottom trawling relative to areas periodically closed or open. The most appropriate model for richness included area and year, and mean richness was greatest in the area continuously closed to trawling. Species-specific length composition distributions were calculated from subsampled individual lengths for 31 species. Significant differences in length frequency distributions were observed, with a higher proportion (~65%) of larger fish most often present in areas continuously closed to commercial bottom trawling (20 of 31 species) relative to other areas. Our data suggest that the RCA is an effective management tool for conserving not only rockfishes, but also other demersal fish species.

Assessing population recovery inside British Columbia’s Rockfish Conservation Areas with a remotely operated vehicle

“…Furthermore, none of the features we analyzed explained variation in RR among the RCAs or among species, although we may not have had the power to detect significant effects with a sample size of 38. Several factors may explain the lack of reserve effects (Hamilton et al, 2010;Keller et al, 2014). First, the RCAs were still relatively young when they were surveyed (three to seven years).…”

“…Despite overall declining trends in US west coast groundfish CPUE in a fishery independent trawl survey, higher CPUE and larger fish were found for numerous rockfishes in American RCAs that were continuously closed to trawling (Keller et al, 2014). Spatial fisheries closures may therefore be effective for promoting rockfish population recovery; however, these studies used tools that cannot survey the entire habitat area encompassed by the RCAs (e.g., Keller et al, 2014 used bottom trawls not effective in rocky areas and Hamilton et al, 2010 used SCUBA methods that cannot survey in deeper depths).…”

“…Stoner et al (2008) contend that there is no better way to monitor fishes in structurally complex habitats. ROV surveys can better encompass the entire area of the RCAs than methods used in previous studies (e.g., Marliave and Challenger, 2009;Hamilton et al, 2010;Cloutier, 2011;Keller et al, 2014). ROV surveys targeting deeper-dwelling species were also undertaken in the Channel Islands within the first five years after establishment; the authors compared the density of fishes on hard-bottom substrates between 20 and 100 m in depth among three sites pairs inside and outside of reserves (two other site pairs were dropped) (Karpov et al, 2012).…”

Pacific Canada&#8217;s Rockfish Conservation Areas: using Ostrom&#8217;s design principles to assess management effectiveness

“…Some ecological studies suggest that RCAs are having a positive impact on rockfish populations within protected area boundaries (Cloutier 2010); however, the majority of studies are currently inconclusive. When compared with the ecological success of RCAs created in 2002 on the U.S. West Coast (Keller et al 2014), Canadian RCAs have considerable room for improvement. Research is required to understand the differences in the ecological success of RCAs in each country, but the management challenges we address in this paper may play a role in the limited success of Canadian RCAs to date.…”

“…Subsequently, intensive fishing in rocky reef environments can deplete local rockfish populations, making it difficult for species to rebuild even after fishing has stopped (Parker et al 2000). However, because inshore rockfish are typically sedentary with very small home ranges (Table 1; Love et al 2002), spatial protection should be highly effective, and indeed has been along the U.S. West Coast, where rockfish conservation areas had significantly larger populations of rockfish and greater species richness than nearby open areas (Keller et al 2014).…”