SPATIAL VARIATION IN RED-SEA URCHIN REPRODUCTION AND MORPHOLOGY - IMPLICATIONS FOR HARVEST REFUGIA

Red sea urchins (Strongylocentrotus franciscanus), residing in shallow habitats in Bodega Bay, California are morphologically distinct and p ossibly enhance recruitment by spawning larvae and sheltering juvenile s. This suggests shallow beds of urchins would be ideal candidates for harvest refugia promoting the production of larvae to replenish deepe r harvested habitats. Red urchins from shallow beds (5 m) had signific antly heavier gonads (63 +/- 30 g, N = 45, mean +/- I so) compared wit h urchins from intermediate (14 m) and deep (23 m) habitats (12 +/- 8 g, N = 39, mean +/- 1 so). Gonad indices from spring, summer, and fail of 1991 and 1992 show this pattern persisted. Shallow water urchins c o-occurred at high densities (4.6 individuals/m(2)), with seasonally a bundant drift algae and wave surge. Recruitment of juvenile urchins wa s examined in nine 1-m(2) quadrats randomly placed in three shallow si tes with red urchins and three intermediate depth sites with red urchi ns in the Bodega Marine Reserve. Juvenile urchin (Strongylocentrotus s pp.) recruitment (5-50 mm) was highest in association with adults in s hallow habitats over a 4-yr period (October 1988-October 1992). Adult red urchins in shallow habitats resided in rock ''bowls'' where they w ere 12 times more likely to shelter juveniles than more mobile adults in deep water. Principal component analysis identified five morphologi cal characteristics of shallow water urchins: short spines, large gona ds, thick tests, small lanterns, and small peristomial openings. Exter nal morphological characteristics (e.g., spine length) could be used t o ensure the protection of reproductive urchins in shallow harvest ref ugia offering an alternative urchin management strategy for northern C alifornia.