Feasibility of artificial reefs in intertidal waters

Studies were undertaken in 1972 on the potential of artificial reefs in intertidal waters of Humboldt Bay, northern California. Underwater observations were made of two types of "low profile" reef structures, made of car tires, placed near an existing reef located in Southport Channel of South Humboldt Bay. Fish populations around an old shipwreck in intertidal waters of Hookton Channel in South Humboldt Bay were enumerated by sampling with rod and reel and by direct underwater observations. The "low profile" structure I designed proved effective in attracting fish and producing growth of attaching organisms. The structure was not subject to excessive siltation. The shipwreck attracted transient fish populations, with fish entering the area on the incoming tide and leaving on the out-going tide. Over-fishing an intertidal reef is probably more difficult than depleting subtidal reefs which develop a more resident population of fish. Fishing intertidal and subtidal reefs should result in greater fishing success if fishermen can be directed to them at times when seasonal abundance of fish are the greatest. Fish and invertebrates were studied at a proposed site for an intertidal fishing reef in a newly excavated small boat basin near the City of Arcata, located on North Humboldt Bay. Fauna was sampled over a nine month period using beach seines, plankton nets, and benthic grabs. I found evidence that nine species of fish spawn and that the larvae and juveniles of these species feed and grow for extended periods of time in the area. The larvae and juveniles of another eight species, presumably having spawned elsewhere, migrated into the vicinity of the basin to feed and mature. Overlying waters of the basin were abundant with plankton. Benthic fauna was low in diversity but high in numbers of individuals. The design of the artificial reef tested in Southport Channel would presumably be unsuitable to the Arcata Small Boat Basin due to a high siltation rate from the surrounding mud flats into the boat basin.