Fish Colonization and the Effect of Fishing Activities on Two Artificial Reefs in Monterey Bay, California

This study was designed to gather information on the attraction and production of fishes associated with two artificial reefs in Monterey Bay, California, and to investigate a potential management technique of constructing “unmarked” artificial reefs in the vicinity of “marked” artificial reefs to create a refuge for exploitable bottomfishes.

Twenty species of fish, primarily rockfish and surfperch, were observed in underwater transects on both artificial reefs during the study. Recruitment of adult fishes from nearby natural reefs to the artificial reefs was rapid. Juvenile recruitment only occurred in the summer season. Mean densities of fish observed underwater on the marked and unmarked reef were similar in corresponding seasons, although after three seasons a significant reduction in rockfish larger than 20 cm was found at the marked reef. This reduction was assumed to be a result of recreational fishing pressure. Hook-and-line fishing effort resulted in a significantly larger catch-per-unit-effort at the unmarked reef in comparison to the marked reef. Tagging results revealed that of those fish marked and recaptured movement only occurred from the unmarked (unexploited) reef towards the marked (exploited) reef.

Since artificial reefs concentrate and attract large numbers of fishes, and often place local fish populations in an area more easily exploitable, management techniques are needed to protect this resource. This study emphasizes the benefits of constructing unmarked or “hidden” artificial reefs in the vicinity of marked artificial reefs or heavily exploited reef areas.