GROWTH INHIBITION OF RED ABALONE (HALIOTIS RUFESCENS) INFESTED WITH AN ENDOLITHIC SPONGE (CLIONA SP.) By Kirby Gonzalo Morejohn A Thesis Presented to The Faculty of Humboldt State University In Partial Fulfillment Of the Requirements for the Degree Master of Science In Natural Resources: Biology May, 2012 GROWTH INHIBITION OF RED ABALONE (HALIOTIS RUFESCENS) INFESTED WITH AN ENDOLITHIC SPONGE (CLIONA SP.) HUMBOLDT STATE UNIVERSITY By Kirby Gonzalo Morejohn We certify that we have read this study and that it conforms to acceptable standards of scholarly presentation and is fully acceptable, in scope and quality, as a thesis for the degree of Master of Science. ________________________________________________________________________ Dr. Sean Craig, Major Professor Date ________________________________________________________________________ Dr. Tim Mulligan, Committee Member Date ________________________________________________________________________ Dr. Frank Shaughnessy, Committee Member Date ________________________________________________________________________ Dr. Laura Rogers-Bennett, Committee Member Date ________________________________________________________________________ Dr. Michael Mesler, Graduate Coordinator Date ________________________________________________________________________ Dr. Jená Burges, Vice Provost Date ii ABSTRACT Understanding the effects of biotic and abiotic pressures on commercially important marine species is crucial to their successful management. The red abalone (Haliotis rufescensis) is a commercially important mollusc, whose shell surface is frequently populated with bright yellow colonies of Cliona sp., an endolithic sponge known to excavate substrates on which it grows. To determine whether a relationship exists between the growth of red abalone and infestation by Cliona sp., divers with the California Department of Fish and Game surveyed abalone in multiple areas within Mendocino and Sonoma counties. Individual abalone (n = 786) were scored for shell length and relative shell coverage by Cliona sp. Animals were tagged, released and resurveyed one year later (12±2 mo). Statistical analyses of this previously unpublished data demonstrated a significant, inverse correlation between the growth of red abalone and extent of shell coverage by Cliona sp. Red abalone acquiring even minimal infestation by Cliona sp. showed significantly inhibited shell growth, with the growth of smaller abalone affected to a greater degree than larger animals. Further surveys by this author in 2010 and 2011 were conducted to determine whether differences exist between the frequency and extent of Cliona sp. infestation of red abalone located in Humboldt County (n =89) versus Mendocino County (n = 106). The frequency of infestation in these counties was not significantly different, but the extent of Cliona sp. infestation was found to be significantly greater in Mendocino County than in Humboldt County. The results strongly suggest that red abalone growth is inhibited by Cliona sp. infestation and iii that regions of the northern California abalone fishery are differentially impacted by this infestation. iv ACKNOWLEDGEMENTS I would like to extend special thanks to Dr. Sean Craig for providing me this great opportunity, to Dr. Laura Rogers-Bennett for crucial advice, direction, and enthusiasm, as well as supplying much of the data used, and to thank Dr. Robert Van Kirk for his patience, mastery, and unrelenting guidance through the statistical analyses. I also thank Dr. Steven Shultz, Dr. John DeMartini and all of the other California Department of Fish and Game divers who for years collected subsurface data. I greatly appreciate discussions with Dr. John DeMartini, who provided insights on specifics of north coast abalone populations. Thanks also to, Andrew Weltz and Sam Parker for their expertise in and under water, as well as in traversing the steep Humboldt cliffs, and Humboldt State University DSO Rich Alvarez for his training and willingness to make sure this project was done safely. I also thank John Banks for supplying Banks Board surface floats used in data collection. Most of all, I would like to thank my parents, Dr. Brooke S. Kirby and Dr. Louis C. Morejohn. Their guidance and criticism was invaluable in the creation of this thesis, and because they have surely read it more times than they would have liked, I am dedicating it to them. v TABLE OF CONTENTS Page ABSTRACT . iii ACKNOWLEDGEMENTS . v LIST OF FIGURES . vii INTRODUCTION . 1 MATERIALS AND METHODS . 11 RESULTS . 18 DISCUSSION . 23 LITERATURE CITED . 27 PERSONAL COMMUNICATION . 34 vi LIST OF FIGURES Figure Page 1 Map Locations of Humboldt County, Mendocino County, and Hardy Creek.. 3 2 Normal Red Abalone Shell with No Apparent Infestation by Cliona sp. 6 3 Infested Red Abalone Shell Exhibiting Yellow Colonies of Cliona sp. 7 4 Map of Survey Sites in Humboldt County . 14 5 Map of Sampling Sites in Mendocino County . 15 6 Growth of Red Abalone Exhibiting an Absence or Gain of Cliona sp. Infestation . 20 7 Relationship Between Red Abalone Growth Rate and Infestation by Cliona sp . 21 vii 1 INTRODUCTION Commercial and recreational fisheries of abalone (Haliotis spp.) once thrived in southern California, with annual landings surpassing 2,000 metric tons throughout the 1950s and 1960s (Karpov et al. 2000). These fisheries collapsed due to improper management, disease and sea otter predation, and in 1996 they were subsequently closed in all areas south of San Francisco Bay (Karpov et al. 2000, Haaker et al. 2001, Micheli et al. 2008, CDFG Code 5521). Since the implementation of this closure, two of California’s five targeted abalone species, the white abalone (Haliotis sorensini) and black abalone (Haliotis cracherodii), have been placed on the endangered species list (Lundy 1997, Federal Register 66: 103, June 2001, Federal Register 74: 9, January, 2009). In contrast to southern California, the northern California fishery continues to maintain recreational harvests of the most heavily targeted species, the red abalone (Haliotis rufescens; Tegner et al. 1992, Karpov et al. 2000). The continued survival of the northern California fishery is commonly thought to result from longstanding prohibitions against commercial fishing and recreational take by means of SCUBA (Karpov et al. 1998). Recreational fishing has been and remains limited to freediving (breath hold), which limits abalone take to relatively shallow depths and results in deep water abalone refugia. Readily accessible inshore abalone populations are thought to be replenished in part by the spawning and migration of deep water animals into shallower water habitats (Ault and DeMartini 1987, Karpov et al. 1998). This fishery is heavily monitored by annual fishery-independent SCUBA surveys, 2 shore-based creel surveys, mandatory abalone report cards, and telephone surveys (CDFG: Abalone Recovery and Management Plan). The SCUBA surveys are conducted by the California Department of Fish and Game (CDFG) in multiple areas within Sonoma and Mendocino counties, and while these two counties account for the bulk of California’s total abalone landings, thousands more are taken from outside of county borders (CDFG: Abalone Report Card Data and Information 2009). In nearly every year during the period 2002-2009, more than 5,000 abalone were taken from Humboldt County (CDFG: Abalone Report Card Data and Information 2009). Among the five coastal counties in northern California, Humboldt County has the largest expanse of coastline, with infrequent rocky reefs scattered within large expanses of sandy beaches. Recreational diving in Humboldt County is known for its remoteness and the difficulty of coastal access, with lower abalone densities and poor freediving conditions along with low visibility and strong surf (Friedman and Finley 2003, pers. obs.) A marked change in oceanic conditions occurs approximately 37 km south of the Mendocino-Humboldt County border, near Hardy Creek (John DeMartini pers. comm.) (Fig. 1). South of this area the conditions are generally better for diving, with clearer and calmer waters (John DeMartini pers. comm.). Abalone residing south of Hardy Creek are found at depths of up to 25 m, whereas animals to the north are rarely found deeper than 6 m (Tegner et al. 1992, John DeMartini pers. comm.). The shallow depth- wise distribution in the latter area allows freediver access to virtually all abalone, and deep-water refugia appear to be absent (John DeMartini pers. comm.). The lack of deep- water refugia for the Humboldt County population may make these populations 3 Figure 1. Map Locations of Humboldt County, Mendocino County, and Hardy Creek. 4 especially vulnerable, requiring close monitoring to ensure maintenance of healthy populations. Many marine invertebrates exhibit non-linear growth rates over their life span. Different size classes of a given species may exhibit very different growth rates, which require the use of non-linear growth modeling (Day and Fleming 1992, Rogers-Bennett et al. 2007). Rogers- Bennett et al. (2007) derived red abalone growth rates from tag- recapture data, estimating years to reach minimum legal size (MLS) to be 12.4±1 y (Rogers-Bennett et al. 2007). Protecting larger size classes has been shown in some species to have the greatest positive effects on population growth (Gotelli 1991, Heppell et al. 2006). In a study performed by Rogers-Bennett and Leaf (2006) examining red abalone, the pattern of larger, mature size classes having greater impacts