Identification and First Documentation of Larval Rockfishes in Southeast Alaskan Waters Was Possible Using Mitochondrial Markers but Not Pigmentation Patterns

Abstract

More than 30 species of rockfish (genus Sebastes) occur in Alaskan waters, but their larvae generally cannot be identified by morphology. Consequently, knowledge of life histories is incomplete for this commercially and ecologically valuable taxon, and the locations and habitats of the larvae of specific species have not been determined. We used mitochondrial DNA markers, which now can delineate most Alaskan rockfishes, to identify larvae collected in ichthyoplankton surveys conducted in Southeast Alaskan waters. We report the occurrence of 15 species or species groups. Sebastes zacentrus (sharpchin rockfish), S. proriger (redstripe rockfish), and members of the indistinguishable group S. variegatus (harlequin rockfish)−S. wilsoni (pygmy rockfish)−S. emphaeus (Puget Sound rockfish) were observed every year and in most collections in Chatham Strait and along western Prince of Wales Island. Sebastes zacentrus was abundant only in Chatham Strait; S. auriculatus (brown rockfish) and S. elongatus (greenstriped rockfish) were abundant only along Prince of Wales Island. All of the larvae detected occur in Southeast Alaskan waters as adults. In addition, we investigated whether pigmentation patterns can be used for visual identification. Larvae were divided into groups of similar pigmentation distribution and identified by means of mitochondrial markers. Pigment patterns on preflexion larvae do not appear to offer an effective way of identifying the species. Only the patterns of S. maliger (quillback rockfish) and S. caurinus (copper rockfish) in the subgenus Pteropodus were unique, and those patterns may be diagnostic for that subgenus. Intraspecific variation in pigmentation probably reflects a combination of ontogenetic change and adaptive responses to environmental variation.