Landels-Hill Big Creek Reserve

01 Apr, 01 PM - 03 Apr, 08 AM

Activities: I plan to conduct initial surveys of Lottia gigantea density and size structure in rocky intertidal sites in the reserve. I will also scope sites for placement of tuffy pads or tiles as recruitment collectors. Purpose of research project: to determine how recruitment, density and size structure vary inside, just outside and far outside a reserve for exploited intertidal organisms with a variety of dispersal regimes. Research objectives: A growing body of research demonstrates that marine reserves can help protect species that are vulnerable to harvest or other human activities. Analysis of existing studies on marine reserves shows that both abundance and average size of exploited species are generally larger within reserves than outside them (Halpern 2003). While most reserve studies have focused on commercially harvested, subtidal species, rocky intertidal organisms are affected by human activities as well, even where these species are not commercially harvested. Many intertidal invertebrates are collected by recreational users, and others are susceptible to damage due to trampling in heavily visited intertidal areas. On the coast of California, human activities have been shown to reduce the density and average size of many intertidal species (Addessi 1994, Roy et al. 2003). While California boasts a large number of coastal reserves, many of these reserves offer little actual protection to intertidal species, as the laws protecting these species from collection are rarely enforced. However, in those reserves that are adequately protected, intertidal organisms may reach much higher abundances and maximum sizes than those achieved outside the reserve boundaries (Kido and Murray 2003, Roy et al. 2003). The viability of exploited intertidal species may depend in part on the adequate protection of individuals within existing reserves and the spillover of recruits from reserves to other areas. The extent of spillover outside of a marine reserve depends on not only adequate protection within the reserve, but also the size of the reserve and the dispersal regime of the species. Because marine intertidal species often have low mobility as adults, spillover from reserves to surrounding areas may depend largely on export of larvae. Therefore, to examine the spillover effect it will be necessary to look not only at adult populations inside and outside reserves, but also at larval recruitment at all sites. Intertidal species affected by human activities vary from those with crawl-away larvae, such as many whelks, to species with pelagic larval durations (PLDs) of several weeks. This study will use a suite of species with a variety of dispersal scales to help determine how species recovery and spillover depends on dispersal. The effects of the protected areas will also depend on how adult density affects fecundity and recruitment success. Hypothesis: In general, population sizes of exploited species will be higher and individuals of these species will be larger within reserves than outside of them, and abundance will be higher just outside reserve boundaries than far outside of them. In the small coastal reserves in this study, the spatial extent of protection may be much smaller than the dispersal potential of some species. Therefore, species with a relatively short dispersal distance are likely to show the greatest increase in abundance inside versus outside of reserves, and are more likely to show a spillover effect than species with longer distance dispersal. Experimental Design: This study will compare a variety of rocky intertidal sites, including sites inside reserves, just outside the boundary of the reserves, and far from the reserves. A set of well-protected reserves spanning the California coastline will form the focal point of the study, and a number of sites both within and just outside the reserves will be selected. For each reserve, reference sites in nearby areas, accessible to recreational visitors and open to collecting, will be chosen for similarity in topography, wave exposure, and other factors that may influence community structure. At each site I will measure population abundance, size structure, and recruitment. Species: A number of intertidal species, representing a range of dispersal regimes, will be selected. These species are subject to collection for recreation, food, or bait. Many of these species have already been shown to be reduced in abundance or size in exploited areas. Potential species of interest include Lottia gigantea, Haliotis cracherodii, Aplysia californica, Tegula funebralis, Stenoplax conspicua, Tonicella lineata, Asterina miniata, Astrea undosa, Strongylocentrotus purpuratus, Strongylocentrotus franciscanus, and Mytilus californianus. Methods: At each study site, 30 meter transects will be run parallel to shore in the low, mid, and high zone. Using a ? m2 quadrat placed at each meter mark, I will count all the individuals of selected invertebrate species to determine abundance. For uncommon species, I will also measure each individual in the quad to determine size structure. For highly abundant individuals, I will use a random number generator to select 50 locations along the transect and measure the three individuals closest to each point, to determine size structure from 150 randomly selected individuals. In addition, to assess the abundance of the largest (and most fecund) individuals in particular, I will conduct timed searches throughout the entire site, and count and measure only individuals over a threshold size. Tuffy pads and tiles will be used as settlement collectors to determine the amount of recruitment at each location. These methods are currently employed by PISCO researchers, who regularly monitor recruitment at sites throughout the west coast, including sites within my proposed study areas. Where possible, collectors in place for PISCO studies will be utilized. Where PISCO collectors are not in place, I will place three replicates of each collector at each site. I will process the collector and count recruits monthly, to capture temporal as well as spatial variation in recruitment. To determine the species of settling limpets I will develop a molecular probe to identify limpet recruits. Anticipated significance: This project will help researchers and managers understand how species with different dispersal regimes respond to reserves, and how large a reserve is necessary to see a population response and spillover effect, both important questions for the design of marine reserve networks. The results of this study may also demonstrate the importance of the UC Natural Reserve System reserves in protecting populations of rocky intertidal invertebrates and enhancing populations of those species outside the reserves.

Visit #6948 @Landels-Hill Big Creek Reserve

Approved

Under Project # 4721 | Research

The influence of dispersal regime on larval export of intertidal species in California

graduate_student - University of California, Santa Barbara

Reservation Members(s)

Group of 2 Graduate Student Apr 1 - 3, 2005 (3 days)

Reserve Resources(s) | Create Invoice

Redwood Camp 2 Apr 1 - 3, 2005