Larval abundances of rockfishes that were historically targeted by fishing increased over 16 years in association with a large marine protected area

Abstract

Marine protected areas (MPAs) can facilitate recovery of diminished stocks by protecting reproductive adults. To effectively augment fisheries, however, reproductive output must increase within the bounds of MPAs so that larvae can be exported to surrounding areas and seed the region. In response to dramatic declines of rockfishes (Sebastes spp.) in southern California by the late 1990s two large MPAs, the Cowcod Conservation Areas (CCAs), were established in 2001. To evaluate whether the CCAs affected rockfish productivity we evaluated the dynamics of 8 species that were, and 7 that were not, historically targeted by fishing. Abundances of 6/8 targeted and 4/7 non-targeted species increased regionally from 1998 to 2013. These upturns were probably affected by environmental conditions in addition to changes in fishing pressure as the presence of most species correlated negatively with temperature, and temperature was lower than the historic average in 11/15 years. Seventy-five per cent of the targeted, but none of the non-targeted species increased at a greater rate inside than outside the CCAs while controlling for environmental factors. Results indicate that management actions, coupled with favourable environmental conditions, facilitated the resurgence of multiple rockfish species that were targeted by intense fishing effort for decades.

Seasonal distribution of late larval and juvenile rockfish (Sebastes spp.) and associated environmental conditions off Oregon and Washington: new insights based on genetics

“…These unidentifiable groups include larval smelts (7 species in the family Osmeridae), rockfishes (65 species), sanddabs (2 species of the genus Citharichthys), and snailfishes (17 species of the genus Liparis) Matarese et al, 1989;Love et al, 2002;Auth et al, 2011). Our work off the coast of Oregon, like previous research in and around Southern California (Taylor et al, 2004;Thompson et al, 2016;Thompson et al, 2017), has helped illuminate the diversity of the largest of these previously unidentifiable groups of fishes.…”

“…However, there remain some species (i.e., the WEVZ complex) that cannot be resolved to species level with the cytochrome b database of known samples. Analysis down to the species level for collections that contain a high proportion of rockfish (e.g., Thompson et al, 2016) can provide valuable information for ecosystem-based fishery management. Identifying Sebastes larvae to species may allow estimates of spawning biomass of the more abundant species (Ralston et al, 2003;Ralston and MacFarlane, 2010) and enable managers to track recruitment over time .…”

“…Sequence-based identification methods have been previously used to identify morphologically unidentifiable rockfish larvae and to relate distributions of these larvae to oceanographic features and natal habitat (Taylor et al, 2004;Hitchman et al, 2012;Thompson et al, 2016;Thompson et al, 2017), to describe the early development of larval rockfishes , and to describe the early life history among lesser-known species (Yu et al, 2015). As with previously published research in Southern California utilizing cytochrome b sequencing, we identified 2509 rockfish from 24 different taxa and the 4-species WEVZ complex (plus 25 unknowns), and therefore adding this approach greatly increased the level of species identification and distribution details that could be made available.…”

“…Although some of these patterns have been previously identified, we were able to expand our identifications to include a much greater diversity of species, including many of those that are unidentifiable by visual means. This newly described diversity was then related to environmental factors, such as ocean temperature, upwelling intensity, and productivity regime (PDO and NPGO indices), and season to explore temporal and spatial drivers of species diversity or mating success (Taylor et al, 2004;Thompson et al, 2016;Thompson et al, 2017). Although a detailed seasonal and annual analysis of the abundance and distribution patterns of rockfish species is beyond the scope of this study, we did observe some months and years where individual species showed greater prominence through the indicator species analysis.…”

“…Settlement to the bottom occurs after a period of a few months to a year, and varies by species (Love et al, 2002). Larval and pelagic-juvenilestage rockfish represent a significant proportion of the ichthyoplankton and micronekton community off Washington, Oregon, and California (Auth, 2009;Phillips et al, 2009;Thompson et al, 2016;Thompson et al, 2017).…”