Analysis of fish populations at platforms off Summerland, California.

Abstract

1) The fish assemblages found around the Summerland platforms are similar to those around other
platforms situated in the same bottom depths in the Santa Barbara Channel (i.e., Holly and Gilda);
2) There is substantial overlap in the species living in the midwaters, bottoms, and shell mounds on
many, if not all, of these relatively shallow water platforms. This is at least partially due to a suite of
rockfish species that recruit as YOYs to platform midwaters and are then able to occupy both midwater
and bottom depths;
3) Based on the high densities of juveniles, one of the major functions of the Summerland platforms is
as a nursery ground for a suite of species, primarily rockfishes but also including lingcod and painted
greenling. Adult fishes (e.g., blacksmith, cabezon, garibaldi, and sheephead) are present, sometimes
in substantial numbers, but juvenile rockfish dominance relegates these other species to a relatively
small fraction of the total fish population.
4) The densities of fishes in the midwaters of most California platforms vary greatly between years,
regardless of platform bottom depth, because juvenile rockfish recruitment varies (sometimes dramatically)
between years. At many shallower platforms (such as those
off Summerland) the three habitat assemblages, which share a variety of juvenile rockfish species, are
linked and thus fish densities at all depths and habitats may vary greatly interannually