Year Around Closed Areas as a Management Tool

Abstract

Year around closed areas or refuges as management mechanisms for controlling fishing mortality are explored using a two-component, spatial model with movement between areas. The model assesses the fate of a cohort when only a portion of it is vulnerable to fishing. The yield per recruit and spawning stock biomass per recruit are compared for equivalent amounts of fishing effort with and without a refuge.The results indicate that the institution of a closed area can lead to substantial increases in spawning stock biomass realized from a cohort and, as such, could be a viable shortterm management option to reduce overall fishing mortality on an overexploited stock. Yield per recruit with a refuge is a complex function of the size of the refuge, fishing mortality rates and movement rates. The results suggest that the proportional loss in yield per recruit will be less than the initial proportion of the cohort contained within the refuge. In some instances, the yield per recruit with a refuge can exceed the yield per recruit without one, but the net increases are usually small. The size of the refuge needed to achieve a specified gain in spawning biomass depends upon the mobility of the fish. Higher movement rates require a larger refuge to achieve the same increase, but any loss in yield per recruit will be less even though the refuge is larger.The assumptions underlying the model are discussed, and the importance of information on movement rates for assessing the possible effect of closed areas is stressed.KEY WORDS: Closed areas, fishery management, refuge, spawning stock biomass per recruit, yield per recruit.

Do marine reserves export adult fish biomass? Evidence from Apo Island, central Philippines

“…In addition, a reasonable number of studies have specifically tried to demonstrate movement of target species from marine reserves to fished areas using tag-recapture technlques, e.g. lobsters (Davis & Dodrill 1980, shrimps (Gitschlag 1986), snow crabs (Yamasaki & Kuwahara 1990) and reef fish (Beinssen 1989, BI-yant et al 1989, Buxton & Allen 1989, Rutherford et al 1989, Holland et al 1993, Attwood & Bennet 1994, Davles 1995 In add~tion, several studies have modeled the potential effects of movemen.ts of adult fish from marine reserve to fished areas on yield per recrult of target species (Polacheck 1990, Russ et al 1992, DeMai-tlni 1993 The establishment of a no-fishing sanctuary that covered 2%) of the fishing ground for snow crabs in Japan led to a 46% increase in mean catch per unit effort in areas adjacent to the sanctuary after 5 yr of sanctuary protection (Yamasaki & Kuwahara 1990). This increase in catch rate was reported to be most evident within 3 miles (ca 5 km) of the boundary of the sanctuary.…”

“…Davis & Dodrill 1989, Alcala & Russ 1990, Bohnsack 1990, Polacheck 1990, Roberts & Polunin 1991, Carr & Reed 1993, DeMartini 1993, Dugan & Davis 1993, Rowley 1994. The major objectives (amongst many others) of the use of marine reserves in management of coral reef fisheries is protection of a cr~tical spawning stock biomass to ensure recruitment supply to fished areas via larval dispersal and possible maintenance or enhancement of yields to areas adjacent to reserves by adult (post-settlement) movements (e.g.…”

Alongshore advection and marine reserves: consequences for modeling and management

“…Polacheck 1990, Quinn et al 1993, Holland & Brazee 1996, Lauck et al 1998, Hastings & Botsford 1999, Mangel 2000, Gerber et al 2003. Although these models provide valuable insight into the effects of marine reserves on fish populations and serve as a baseline for future studies, most of them do not address the problem of larval dispersal in a realistic way ).…”

Quantifying and Monitoring Ecological Response to No-Take Marine Reserves

“…For reserves aiming to protect finfish, many models are available, however one of the simplest (and therefore broadly applicable) by Polacheck (1990) could be used in lieu of Hastings & Botford (which assumes that all adults are sedentary) to provide an estimate of reserve size necessary to attain conservation and fisheries goals. Polacheck's model has been used in recent MPA related fisheries studies (e.g.…”