Human Visitation and the Frequency and Potential Effects of Collecting on Rocky Intertidal Populations in Southern California Marine Reserves

Humans intensely use southern California rocky shores for recreational activities such as fishing, exploration, wallung, enjoyment of the out-of-doors, and educational field trips. People also collect intertidal organisms for consumption, fish bait, home aquariums, and other purposes. In Orange County, visitors concentrate their activities on a few rocky headlands and reefs. Many of these shores have been designated as California Marine Life Refuges (CMLRs) or State Ecological Reserves (SERs), where the removal of most intertidal organisms, except for scientific purposes, has been unlawful for 30 years. In a yearlong study of eight Orange County shores, unlawful collecting of organisms was often observed. In addition, lifeguards have frequently observed unlawful collecting on these and other shores. The CMLR or SER designation &d not deter collecting. Mussels, trochd snails, limpets, urchins, and octopuses were the most commonly collected organisms, primarily for food or fish bait. Several of the gastropod species targeted by human collectors had low population densities and population structures dominated by smaller and less fecund individuals, characteristics that often occur in populations exploited by humans. Most collected invertebrates were broadcast spawners that require high densities of fertile individuals to optimize reproduction. The cascading effects of collecting on community structure and the reproductive success of exploited populations are unknown. Except for state park rangers at one site, no state enforcement personnel were seen during 768 hours of low-tide observations throughout the year. Without effective enforcement, adequate signage, and educational programs to increase public awareness, CMLRs and SERs are not protecting rocky intertidal populations on heavily visited southern California shores. Improved management practices are needed if CMLRs and SERs are to protect rocky intertidal populations and to serve as benchmark sites where changes in populations due to regional climatic events or chronic human disturbances can be measured and evaluated in the absence of exploitation. INTRODUCTION The human population residing in the coastal zone is growing by more than 1% per year in the United States (Culliton et al. 1990). This growth has been particularly rapid in coastal southern California counties, where the population has increased by more than 50% over the past three decades (Anon. 1969, 1998). The disturbance produced by the activities of this expanding population is thought to have resulted in a widespread reduction in the biodiversity of southern California’s rocky shores (e.g., Littler 1980; Littler et al. 1991; Murray and Bray 1994). Previously, declines in rocky intertidal biodiversity have largely been ascribed to chronic, persistent disturbances including discharged sewage and industrial effluents (Dawson 1959, 1965; Widdowson 1971; Thom and Widdowson 1978; Littler 1980). But more episodic disturbances resulting from visitor foot traffic (Brosnan and Crumrine 1994; Keough and Quinn 1998); the collection of organisms for human consumption, fish bait, aquariums, and other purposes (Griffiths and Branch 1997); and the exploratory manipulation of rocks and specimens (Addessi 1995) can also significantly affect rocky intertidal populations and communities. Yet, little attention has been given to the effects of human visitation, despite the large numbers of people that use southern California rocky shores throughout the year for activities such as recreational fishing, food and specimen gathering, educational field trips, exploration, walking, and enjoyment of the out-of-doors. Globally, marine protected areas (MPAs) are receiving increasing attention as management tools for protecting marine populations &om human activities (Gubbay 1995; Ticco 1995; Agardy 1997). In the last fifteen years, the number of MPAs has grown from about 400 to more than 1,000 worldwide (Gubbay 1995). Along the heavily urbanized southern California mainland, California Marine Life Rehges (CMLRs), State Ecological Reserves (SERs), and Marine Resources Protection Act (MRPA) Ecological Reserves are the most common MPAs established to protect intertidal organisms from on-site visitor disturbance (McArdle 1997). Although minor variations occur among sites, CMLRs and SERs prohbit the removal of almost all marine plants and invertebrates except with a scientific permit or special authorization by the California Department of Fish and Game (Smith and Johnson 1989; McArdle 1997). Exceptions generally include invertebrates of historical importance to recreational sport and commercial fishers,