Fish Bulletin 124. Artificial Habitat in the Marine Environment
- Author(s): Carlisle, John G, Jr.;
- Turner, Charles H;
- Ebert, Earl E
- et al.
It has long been known that greater numbers and kinds of fishes inhabit rocky coasts, reefs, and banks than smooth, unbroken sandy or muddy bottoms, and that shipwrecks provide excellent fishing in otherwise non-productive areas. On this basis, various state and private agencies have placed old automobile bodies and other objects in areas generally barren of sportfish. Reports have indicated greatly increased sportfish yields in these areas, but to our knowledge, no full-scale scientific evaluation of artificial reefs has been made. The Japanese have done some work in this field, but their results are unpublished. With these facts in mind, the California Department of Fish and Game instituted a study of artificial reefs in April 1958. Many flat, sandy or muddy areas occur along the southern California coast, often near small-boat harbors. While large party, charter, and private boats can travel long distances to offshore islands and productive headlands, these fishing grounds are beyond the range of small-boat fishermen. The chief value of artificial reefs is to provide owners of small boats with good fishing near a harbor. With California's population increasing at a tremendous rate each year and recreation needs multiplying at an unprecedented pace, coastal fishing assumes an ever more important role. Pollution of these same waters, especially by industrial wastes, is constantly decreasing the yield of once productive areas. Kelp beds, of great importance in the ecology of the region, have diminished or virtually disappeared in the path of these pollutants, with consequent decreases in suitable fish habitat. In addition, several successive years of above average water temperatures drastically reduced vast areas of kelp beds along our shores. Sea urchin predation on the reduced beds has been widely observed by divers. To determine the true value of artificial reefs, we carried out routine diving so we could observe and obtain as much information as possible on the numbers and kinds of fishes occurring around artificial habitat. Kelp growth, numbers and species of invertebrates, animal behavior, and many other observations also have been made. The theory of attraction of fishes to solid objects (thigmotropism) is discussed by Breder and Nigrelli (1938), and probably explains some of the success of artificial reefs in attracting and holding fishes. Observations made during the Department's Kelp Investigations Program at Scripps Institution of Oceanography (Quarterly Progress Reports), and our observations of fishes following a young giant kelp plant, Macrocystis pyrifera, drifting across a semi-barren sand bottom, and of fishes attracted to artificial reefs and offshore oil installations definitely support this theory. Breder and Nigrelli (1938) described thigmotropism as the "desire" of fishes to be close to a solid object. The attraction of fishes to each other (schooling behavior) also becomes a necessary explanation of reef success. Finally, availability of shelter and food help explain the attractiveness of artificial habitat. As part of our investigation of man-made marine environment, we also undertook a study to evaluate the effects of offshore oil drilling installations.