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Currently Skimming:

Empirical and Modeling Studies of Marine Reserves
Pages 71-96

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From page 71...
... Consequently, policies may fail to protect some habitats and species. As a management tool, reserves have both disadvantages and advantages when applied to the diversity of marine species and habitats.
From page 72...
... reserves provide unique sites for education and research on marine ecosystems, especially for comparison to areas altered by human activities; and 5. reserves provide "control" areas for determining natural mortality rates for different life-history stages, rates that are critical variables in stock assessment models (Box 5- 1)
From page 73...
... ~[ 4~ Age- 3~ oF ~~ R~ Rcsc~cs also can sac i~oda~ Cinchona in baits Son peaces. Rcsc~cs act as controls (un~s~cd altos)
From page 74...
... The movement toward an ecosystem approach to managing marine species gained momentum when habitat became a central theme of the MagnusonStevens Fishery Conservation and Management Act (MSFCMA)
From page 75...
... , some of which are quantifiable through development of abundance indices (Koenig and Coleman, 1998~. Establish Replenishment Zones A marine reserve has the potential to play an important role in replenishing exploited marine ecosystems through the dispersal of larval or adult fish from the closed areas into regions where fishing is allowed (DeMartini, 1993~.
From page 76...
... in southwest England have resulted in increased yields by enhancing juvenile survival, even though neither area is completely closed (Horwood et al., 1998~. Provide Insurance Against Uncertainty Insurance against the collapse of fish stocks is a primary, but elusive, goal of marine fishery management.
From page 77...
... Fishery management is not the only source of uncertainty in complex, poorly understood marine ecosystems. For example, many estuaries, coastal ecosystems, and coral reefs are threatened by a variety of anthropogenic activities that include shipping, dredging, petroleum extraction, shoreline development, wetlands destruction, river and stream diversion, exotic species introductions, and pollution.
From page 78...
... Marine reserves could provide a mechanism for ensuring preservation of habitat areas of particular concern (HAPCs)
From page 79...
... Careful studies at these reserves allowed researchers to gather quantitative evidence that closed areas could be used in marine conservation to restore or maintain a more natural ecosystem structure and to facilitate local recovery of depleted fish stocks (Russ, 1985; Ballantine, 1991; Castilla, 1999~. These initial studies indicated that establishing reserves had diverse effects, including rapid buildup in biomass (numbers and average body size)
From page 80...
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From page 81...
... For example, in and around Belize's Hol Chan Marine Reserve, fish densities increased in only a few families while fish biomass increased significantly after three years of closure (Polunin and Roberts, 1993; Carter and Sedberry, 1997~. Biomass of economically important fish species increased two-fold in peripheral parts of the reserve and nine-fold in the center of the reserve compared to fished areas (Roberts and Polunin, 1994~.
From page 82...
... For example, the Looe Key National Marine Sanctuary in Florida supports six species of economically valuable fish that are absent from surrounding exploited
From page 83...
... EMPIRICAL AND MODELING STUDIES OF MARINE RESERVES TABLE 5-2 Characteristics That Render Marine Species Vulnerable to Extirpation and Extinction 83 Vulnerability Characteristics High Low Population Turnover Longevity Long Short Growth rate Slow Fast Natural mortality rate Low High Production biomass Low High Reproduction Reproductive effort Low High Reproductive frequency Semelparity Iteroparity Age or size at sexual maturity Old or large Young or small Sexual dimorphism Large differences in size between sexes Does not occur Sex change Occurs Does not occur Spawning In aggregations at predictable locations Not in aggregations Allee effectsa at reproduction Strong Weak Capacity for recovery Regeneration from fragments Does not occur Occurs Dispersal Short distance Long distance Competitive ability Poor Good Colonizing ability Poor Good Adult mobility Low High Recruitment by larval settlement Irregular and/or low level Frequent and intense Allee effectsa at settlement Strong Weak Range and Distribution Horizontal distribution Nearshore Offshore Vertical depth range Narrow Broad Geographic range Small Large Patchiness of population within range High Low Habitat specificity High Low Habitat vulnerability to destruction by people High Low Commonness and/or Rarity Rare Abundant Trophic Level Rare Low a Allee effects occur when a reduction in population density has significant impacts on reproduction. SOURCE: Roberts and Hawkins, 1999.
From page 84...
... There are few studies demonstrating the replenishment of fish stocks on fishing grounds via export from reserves (Bustamante and Castilla, 1990; Tegner, 1993; Roberts, 1995~. In some cases, this lack of data feeds the skepticism of the fishing community, but for some intensively fished species, models indicate that reserves have a high probability of increasing yields (see Attwood and Bennett, 1994; Murawski et al., 2000~.
From page 85...
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From page 87...
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From page 88...
... The increase in reproduction derives from increased abundance of larger, older, more fecund females in the population. Characteristics of Larval Dispersal Most marine species exhibit considerable interannual recruitment variability (Dayton and Tegner, 1990~.
From page 89...
... On Georges Bank and in the Gulf of Maine, more than 5000 nmi2 were closed to bottom trawling and dredging in December 1994 in response to the critical decline of groundfish stocks. The intent was to improve recruitment by reducing bycatch of juveniles and preventing the disturbance of juvenile habitat in the closed areas.
From page 90...
... Larval Dispersal Distances Dispersal is facilitated for marine species having a planktonic larval stage. In fact, larvae of coastal species frequently appear in mid-ocean plankton samples (Scheltema, 1986~.
From page 91...
... If larval dispersal is low, even for species with planktonic larvae, then marine species, including some fishes, may require management on much finer spatial scales than previously assumed. Dispersal distances will affect the larval spillover distances to surrounding areas with implications for designing reserve networks that are self-sustaining (Figure 5-2~.
From page 92...
... Palumbi (in review) used a similar approach to estimate average larval dispersal for a variety of marine species.
From page 93...
... by measuring adult abundance, post-larval supply, juvenile density and nursery habitat. Evaluating these factors is critical for choosing a marine reserve site that will function as a source for the surroundings.
From page 94...
... A combination of conventional management tools and reserves in spawning and nursery areas may be needed for some species. Reducing Risk of Population Collapse The concept of using reserves as buffers against overfishing has been explored to an extent using simulation models of fluctuating populations when catch rates are imperfectly controlled (e.g., Guenette and Pitcher, 1999; SladekNowlis and Roberts, 1999; Crowder et al., 2000~.
From page 95...
... Whereas many coral reef fish have small territories as adults and may disperse during their planktonic larval stage, numerous fish species migrate hundreds or even thousands of kilometers annually (Harden Jones, 1968~. Many high-value fish species, including cod (Gadus morhua)
From page 96...
... . Marine reserves clearly offer a reliable means to protect habitat, especially where fishing gear has been shown to destroy fragile, slow-growing, biogenic habitat such as corals.


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