Larvae define spawning habitat of bocaccio rockfish Sebastes paucispinis within and around a large southern California marine reserve

摘要

Identifying sources of larval production and subsequent dispersal paths is critical for evaluating the efficacy of marine protected areas. We assessed whether the Cowcod Conservation Area (CCA), the largest oceanic reserve in the Southern California Bight (SCB), established to conserve cowcod Sebastes levis, protects essential spawning habitat of another overfished rock fish, bocaccio S. paucispinis. To this end we investigated relationships between age-specific (recently hatched, preflexion and postflexion) larval distribution and abundance, environmental indicators (temperature, chlorophyll a), and depth between 2002 and 2004. Larval presence was consistently higher in the CCA than in surrounding areas of the SCB. Abundances of bocaccio lar vae from all size classes peaked in 2004, which had relatively low sea surface temperature and high chlorophyll a. Depth and sea surface temperature or chlorophyll a were significantly related to the presence of recently hatched larvae, which were most common in cooler western CCA waters where chlorophyll a tended to be highest. In contrast, later stage larvae were not signifi cantly related to depth, indicating that they had been advected from natal locations. Examination of current patterns and the distribution of older larvae suggested that the direction of larval trans port varied among years, with mostly northwestward transport in 2002, a cyclonic recirculation feature that may have retained larvae within the CCA in 2003, and southwestward transport in 2004. These results demonstrate that spatial and temporal oceanographic heterogeneity affect lar val distribution and transport in this region. We conclude that the CCA protects essential bocaccio spawning habitat and is an important source of bocaccio production in the SCB.