Distribution and Abundance of Nearshore Larval Fishes in Central California with Special Emphasis on Rockfish (

Larval fish were collected using 335 micron mesh nets on a 0.71 m (2.33 ft) diameter bongo frame off central California approximately every six hours over a 24 hour period once per month from July 2008 through June 2009. Samples were collected by lowering the nets from the surface to near the bottom and then retrieved to the surface, with this being repeated until a target volume of water had been filtered through the nets. The overall study zone was divided into seven sampling areas with each area being farther offshore than the previous one. Two samples were collected in each area during each of the six hour cycles. The width of the sampling area was approximately 1 km (0.6 miles) alongshore with the total offshore extent being approximately 2.9 km (1.8 miles). The average depth at the offshore boundary of the outer station was approximately 61 m (200 ft). About 36,000 larval fish were collected and identified from the samples. This sampling regime allowed a determination of both the composition and abundance of larval fish at varying distance from the shoreline. Highest densities of all larvae combined was observed during the spring, although some taxa were more abundant during the winter or summer. Preflexion rockfish larvae can generally not be visual identified to the species level but in the lab can be placed into two groups based on pigmentation patterns. A sample of the rockfish larvae from each pigment group collected in all of the areas was identified to species using DNA analysis. The results were used to estimate the nearshore distribution of the individual rockfish species. In most instances the larval distribution along the onshore to offshore depth gradient derived from speciation using DNA mirrored the adult depth distribution.