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The association between the black rockfish Sebastes melanops Girard and beds of the giant kelp Macrocystis integrifolia Bory in Barkley Sound, British Columbia

University of British Columbia

The association between the black rockfish, Sebastes melanogs Girard and the giant kelp, Macrocystis integrifolia Bory, was examined in terms of habitat utilization. Distributional patterns of juveniles frequenting kelp beds were documented by three-dimensional positioning of observed fish with the kelp bed boundaries used as a frame of reference. Significantly higher numbers of smaller (30 - 100 mm) fish occurred inside the kelp bed than outside, both diurnally and nocturnally. A diel migration of larger (101 - 200 mm) fish occurred, showing significantly higher numbers of fish in the kelp bed nocturnally. Very few of the largest (201 - 250 mm) fish were observed in the bed and none of these exhibited this diel shift. Wider-scale sampling indicated an increasing cline in the size of fish when moving from inshore to the open sea. Diet analysis does not indicate dependence by the fish on kelp bed diet items. Transporting experiments failed to demonstrate any significant homing ability within the size-class of fish studied. Artificial habitats employing plastic 'kelp' were constructed to test the assumption that the fish were responding to the amount of physical shelter provided by the kelp. Results show a highly significant numerical response by the fish population, to the changes in the amount of artificial shelter provided. It is concluded that the species utilizes the physical shelter of the kelp bed primarily as a refugium from nocturnal predators. The value of the kelp bed to the species lies in its enhancement of recruitment through increased survival of the 0 to I age-classes of fish.

Text

2010-02-11

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http://hdl.handle.net/2429/20087

Animal Science

University of British Columbia

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