Decadal-scale observations of marine reserves suggest that indirect effects on taxa that occur through cascading trophic interactions take longer to develop than direct effects on target species. Combining and analyzing a unique set of long-term time series of ecologic data in and out of fisheries closures from disparate regions, we found that the time to initial detection of direct effects on target species (±SE) was 5.13 ± 1.9 years, whereas initial detection of indirect effects on other taxa, which were often trait mediated, took significantly longer (13.1 ± 2.0 years). Most target species showed initial direct effects, but their trajectories over time were highly variable. Many target species continued to increase, some leveled off, and others decreased. Decreases were due to natural fluctuations, fishing impacts from outside reserves, or indirect effects from target species at higher trophic levels. The average duration of stable periods for direct effects was 6.2 ± 1.2 years, even in studies of more than 15 years. For indirect effects, stable periods averaged 9.1 ± 1.6 years, although this was not significantly different from direct effects. Populations of directly targeted species were more stable in reserves than in fished areas, suggesting increased ecologic resilience. This is an important benefit of marine reserves with respect to their function as a tool for conservation and restoration. T he current global trend to increase the number of no-take marine reserves is a phenomenon with complex ecologic, scientific, and socioeconomic dimensions (1-3). Stakeholders want to know how rapidly changes will occur after protection, even if natural variability can be large and difficult to predict. Patterns of variation in recovery rates of harvested species determined from long-term empirical studies can provide these important ecologic insights. Studies that have quantified the rate at which recovery of targeted species may take place have found the main factors affecting the recovery rates of populations in reserves to be the following: initial population size, intrinsic rate of increase (r), stock recruitment relationships, size of reserve, metapopulation structure, relationships with source locations, annual variations in success of individual recruitment events, the success of reducing fishing mortality (F) in the reserve (4-6), and the degree to which fishing has affected populations. Most of these factors relate to population growth, suggesting that recovery is a cumulative process. In addition, the design of reserves and rates of movement across reserve boundaries frequently play a strong role (4
ABSTRACT. Along the coast of the California Channel Islands, USA, the abundant black abalone Haliotis cracherodii began to die in large numbers in 1985. This die-off has spread to most of the islands and still continues. Analysis of the changes in abalone abundance at numerous locations suggests that this is the result of an infectious disease spreading slowly from the south side of Santa Cruz Island. However, this might not be d u e to a directly transmitted disease and w e have found no agent of infectlon As with many diseases, warm temperatures acted to increase mortality rates. Our results were not consistent with other hypotheses for the decline such as over-harvesting, pollution, or factors related to physiological stresses induced by the strong El Nirio of 1983-84, including warm temperatures, starvation and competition.
The black dbalone Hal~otls cracherodil was once abundant in many lntert~dal habitats in southern Callforn~a USA Beginning In 1985 however, black abalone In southern California suffered mass moltal~ties attributed to a condltton telmed lvlthenng syndrome The mass mortalities and w~therlng hyndrome were confined to southern Califoinla except for Dlablo Cove, 70 kin no1 th of Polnt Conception, where mortalities were limlted to the immediate vlcinity of a watm-water dtscharge Beylnnlng In 1992 we monltoied 5 locations along the mainland coast ot central California to detelmine whether mass mortal~ties of black abalone would occur there Abalone numbers decreased at the 3 southern sltes but not at the 2 northern sltes The decline was greatest at the southernmost site Government P o~n t (near Point Concept~on), where there was a 97% reduction in numbers between 1992 and 1995 The 2 sltes ~mmedlately upcoast of Government Polnt, Boathouse and Polnt Arguello, expenenced a 39 to 4Got, decllne ivh~le the 2 northernmost s~t e s (Stalrs and P u n s~m a ) expenenced a s l~g h t increase In abalone All abalone size classes d e c l~n e d at Government Polnt, Boathouse and Point Arguello lndicatlng the decllne was not caused by overharvesting Symptoms of w~therlng syndrome assessed by p u l l~n g on indlv~duals were noted at Boathouse and Polnt Arguello Witheling syndrome was also detected in the flnal survey at Stairs, as lvas a sllght dechne In abalone abundance, suggestlng that mass mortal~ties may be beginning there Our observations demonstrate that w~d e s p r e a d mass mortal~ty assoc~ated w~t h w~t h e l~n g syndlome has reached central Cal~fornia and is progressing northward from Point Conceptlon
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