FEASIBILITY of ARTIFICIAL REEFS in INTERTIDAL WATERS by Andre
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FEASIBILITY OF ARTIFICIAL REEFS IN INTERTIDAL WATERS by Andre DeGeorges A Thesis Presented to The Faculty of California State University, Humboldt In Partial Fulfillment of the Requirements for the Degree Master of Science December, 1972 FEASIBILITY OF ARTIFICIAL REEFS IN INTERTIDAL WATERS by Andre DeGeorges Approved by the Master's Thesis Committee Chairman Approved by Graduate Dean TABLE OF CONTENTS Page ACKNOWLEDGEMENTS ABSTRACT ii LIST OF TABLES iv LIST OF FIGURES vi INTRODUCTION 1 Study Plan 3 Prior Studies 3 DESCRIPTION OF STUDY AREAS 5 Humboldt Bay 5 Southport Channel 6 Fields Landing Wreck 7 Arcata Small Boat Basin 7 MATERIALS AND METHODS 12 Southport Channel 12 Fields Landing Wreck 16 Arcata Smalls Boat Basin 17 Fish Collections 17 Benthos 17 Plankton 18 Analysis of Data 18 RESULTS 28 Southport Channel 28 Fish Fauna 28 Attaching Organisms 28 Siltation 36 Page Fields Landing Wreck 36 Arcata Small Boat Basin 36 Kinds and Numbers of Fish 36 Species of Potential Sport Fishing Interest 55 Seasonal Occurrence by Species 59 Kinds and Numbers of Invertebrates 59 SOURCES OF ERROR 68 Southport Channel 68 Fields Landing Wreck 69 Arcata Small Boat Basin 70 IMPLICATIONS FOR FISHERIES MANAGEMENT 71 Southport Channel 71 Fish and Invertebrates...... 71 Siltation 73 Fields Landing (A Simulated Intertidal Artificial Reef) 74 Pros and Cons of Intertidal Reefs 74 Future Utilization of Artificial Reefs in Humboldt Bay 74 Arcata Small Boat Basin (Potential Intertidal Reef Site) 75 Species of Fish 76 Invertebrate Fauna 76 RECOMMENDATIONS 77 LITERATURE CITED 78 APPENDICES 83 ACKNOWLEDGEMENTS I am greatly indebted to Dr. George H. Allen for bringing the subject of intertidal reefs to my attention and to the City of Arcata for their continued interest in the project. Editorial assistance and recommendations by Dr. Allen, Dr. Boger A. Barnhart, and Dr. M. J. Boyd were particularly helpful in writing this thesis. I would also like to thank Fred Glassey and Dr. John Demartini for their assistance in the identification of invertebrates. Thomas Lambert's identification of subtidal artificial reef invertebrates was greatly appreciated. A large number of fellow students assisted in hook and line fish- ing, beach seining and in placement of reef structures. To all of these individuals, I extend my deepest thanks, especially to Jim Walker, Vic Tanny, and the Over-the-Hill boys. The California Cooperative Fisheries Unit provided space for con- struction and storage of experimental reefs, and aided in their place- ment in Humboldt Bay. ii ABSTRACT 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 de- signed 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 diffi- cult 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 ex- tended periods of time in the area. The larvae and juveniles of another eight species, presumably having spawned elsewhere, migrated iii 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. iv LIST OF TABLES Page 1. Seine hauls for which catch figures were actual counts and those involving estimation of catch from sub- sampling (February-September, 1972) 19 2. Results of tests for independence of subsamples of organisms taken in beach seine hauls at low tide in the Arcata Small Boat Basin (April-September, 1972) 22 3. Example of calculations used in determining the number of individuals per species in beach seine hauls 24 4. Chi-square tests to determine if there was a significant difference between the number of species of fish and in- vertebrates taken in seine hauls at low and high tide 26 5. Summary of observations made while diving on experimental units and main reef structures of Southport Channel (May- September, 1972) 29 6. Growth of attaching organisms on experimental units and main reef structures of Southport Channel (May-September, 1972) 32 7. Number and species of fish caught and hours fished by students with rod and reel on Fields Landing Wreck (Fall, 1971- March, 1972) 38 Page 8. Summary of underwater observations made on Fields Landing Wreck (June-September, 1972) 40 9. Number of fish collected in beach seines fished at low tide in the Arcata Small Boat Basin (February- September, 1972) 41 10. Number of fish collected in beach seines fished at high tide in the Arcata Small Boat Basin (February- June, 1972) 44 11. Number of fish collected in gill nets fished over a six hour tidal cycle in the Arcata Small Boat Basin (January-August, 1972) 47 12. Number of invertebrates collected in beach seines fish- ed at low tide in the Arcata Small Boat Basin (January- September, 1972) 60 13. Number of invertebrates collected in beach seines fished at high tide in the Arcata Small Boat Basin (February-June, 1972) 63 14. Number of invertebrates collected by Eckman Dredge in the Arcata Small Boat Basin (April-August, 1972) 65 15. Classification of invertebrates, by method of feeding, collected in the Arcata Small Boat Basin 92 vi LIST OF FIGURES Page 1. Map of Humboldt Bay showing the general location of study areas .... 2 2. Fields Landing Wreck, Hookton Channel, South Humboldt Bay, at low and high tide 8 3. Map of the Arcata Small Boat Basin indicating the ap- proximate area swept by the beach seine and where gill nets were generally set 9 4. Arcata Small Boat Basin in June, 1972 at a -2.2 low tide and in August, 1972 at high tide 10 5. low profile artificial reef structure, (PL), (March 1, 1972) 13 6. Low profile artificial reef structure, (AD), (January 14, 1972) 7. Sample splitter used to subsample fish and invertebrate fauna collected from the Arcata Small Boat Basin 21 8. Copper rockfish, (Sebastodes caurinus), observing diver off AD structure (July, 1972) 31 9. Underwater photograph of AD structure covered with the hydrozoan, Obelia borealis (August, 1972) 33 vii Page 10. Underwater photograph of PL structure showing scant growth of attaching organisms (May, 1972) 34 11. Underwater photograph of the AD structure showing the hydrozoan, Obelia borealis, and barnacle, Balanus crenatus (August, 1972) 35 12. Breeding rock crabs, Cancer productus, on the AD structure (June, 1972) 37 13. Number of surf smelt taken at low tide by beach seine in the Arcata Small Boat Basin (February-September, 1972) 51 14. Number of Pacific herring taken at low tide by beach seine in the Arcata Small Boat Basin (February-Sept- ember, 1972) 52 15. Number of shiner perch taken at low tide by beach seine in the Arcata Small Boat Basin (February- September, 1972) 53 16. Number of northern anchovy taken at low tide by beach seine in the Arcata Small Boat Basin (February-Sept- ember, 1972) 54 17. Number of staghorn sculpin taken at low tide by beach seine in the Arcata Small Boat Basin (February-Sept- ember, 1972) 56 viii Page 18. Number of jacksmelt taken at low tide by beach seine in the Arcata Small Boat Basin (February- September, 1972) 57 19. Number of topsmelt taken at low tide by beach seine in the .Arcata Small Boat Basin (February- September, 1972) 58 20. Number of mysids taken at low tide by beach seine in the Arcata Small Boat Basin (February-September, 1972) 66 INTRODUCTION In 1971 the City of Arcata with funds from the California Com- mission on Small Craft and Harbors, dredged a sixty-foot wide channel to connect the .Arcata Channel to a small-boat basin excavated just west of the county landfill dump (Figure 1). The purpose of this construction project was to allow citizens access to North Bay, pre- viously unavailable except through Eureka or Samoa boat landings. Montgomery (1971) reported on the feasibility of placing a fishing pier in the small boat basin by the City of Arcata based on a review of the literature. Montgomery identified potential sites for the placement of a pier, a fish-cleaning facility, and artificial reefs to increase the attraction of fish to the area. This plan forsaw much use of such pier fishing as the demand for places to fish in- creases. Pier fishing avoids the expense of boats or elaborate gear and is thus available to all segments of the community.