|
| |
Fishery Benefits of Marine Reserves: A Test in a Florida Recreational Fishery
From: Woods Hole Oceanographic Institution
| By:
Jim Bohnsack |
EDITOR'S INTRODUCTION |
Marine reserves can be controversial for commercial and recreational fishermen, as they see fishing grounds get placed off-limits to fishing. But no-take reserves can be a win-win situation, says Dr. Jim Bohnsack, a research fishery biologist with the National Marine Fisheries Service. Creating protected areas in which fish can live and grow without getting caught, he says, can improve fishery yields in surrounding areas.
Bohnsack provides evidence for using marine reserves in an ecosystem-based management tool by looking at "stealth" reserves that were created for security reasons during the Cold War around the Kennedy Space Center at Cape Canaveral, Florida. He looks at world records for three gamefish species caught around the reserves to show that no-take reserves do help fish species recover and improve fishing in surrounding areas. This is an edited version of a talk Bohnsack gave at the Fisheries, Oceanography and Society Symposium "Marine Protected Areas: Design and Implementation for Conservation and Fisheries Restoration" at Woods Hole Oceanographic Institution in August 2001. |
 provide an empirical test of predictions of marine reserve theory, including the most controversial aspect of the theory--the effects no-take areas on surrounding fisheries. Can closed areas actually increase the catch versus having all areas open under one set of regulations? |
A no-take marine reserve is a type of marine protected area (MPA) that prohibits all fishing and other extraction of living marine organisms except as necessary for essential research and education. Effectively the only things that can be removed are pictures, experiences, memories, data, knowledge, understanding, and appreciation of marine ecosystems. Although the no-take provision offers an objective and very high level of protection, it does not provide total protection from human activities since effects of pollution, global change, and other human impacts can occur. |
Use of marine reserves is just beginning in the U.S. The first planned reserve network was established in 1997 in Florida Keys National Marine Sanctuary (FKNMS) with 18 small (~ 1 km2) and one large (30 km2) ecological reserve composed of multiple ecologically linked habitats. The largest marine reserves in North America were created in 2001 with the establishment of two ecological reserves in the Tortugas region of the FKNMS. Also, an additional ecological reserve, called a research natural area, was approved in 2001 for Dry Tortugas National Park. The total area of these added reserves is almost 200 square nautical miles. Currently, 15 no-take reserve programs exist in the southeastern U.S. In some programs, however, the no-take provision only applies to bottom resources while midwater and surface fishing is allowed for pelagic species. The assumption that the benthos is ecologically decoupled from the midwater and surface components of the water column is a topic that requires further research. |
In theory, reserves provide six main fishery benefits: |
1. Increased total quantity of fish in fishing grounds. Fishing tends to remove the largest species and individuals. A slight increase in average size has profound impacts on total egg production because most aquatic species have an exponential relationship between body length and total egg production. The combination of more and bigger fish in reserves greatly enhances total reproduction, which is dispersed by currents to increase the total supply of juvenile recruits into fishing grounds. |
2. Export of biomass from reserves into fishing grounds. Called spillover, older fish that migrate out of reserves will directly supply surrounding fishing grounds. |
3. Maintain fish quality. Reserves can protect the genetic characteristics of stocks from detrimental selective effects of fishing. Reserves allow genes that are vulnerable to fishing to be maintained in the population. |
4. Reserves provide insurance against natural or human disasters. Reserves provide population refuges that make overfishing more difficult if overfishing occurs in fishing grounds or if natural events prevent successful recruitment for several consecutive years. |
5. More rapid population recovery. A population of reproducing adults in reserves can accelerate stock recovery if overfishing occurs in fished areas or if recruitment fails due to natural events. |
6. More stable annual landings. Spawning stock in reserves can provide more stable reproduction so that fishermen don't have extreme boom and bust cycles in annual landings that characterize many fisheries. |
The model
In theory, protecting a portion of the habitat from exploitation in marine reserves effectively reduces total fishing mortality by eliminating all directed catch, unwanted bycatch, and all habitat damage from fishing. Although initially resources may be depleted or damaged by previous fishing, natural processes allow exploited populations and habitat to recover in reserves. Colonization occurs from individuals that either settle from the plankton or that immigrate from surrounding areas. Individuals in reserves grow and persist while those in fished areas tend to be removed. Abundance and biological diversity of exploited species increases as rare and vulnerable species accumulate. Surrounding fisheries then benefit from spillover and increased reproduction. Spillover occurs as fishes migrate from reserves into surrounding areas where population density and competition are lower and food is more available. A more important fishery benefit is that larger and more abundant fishes in reserves significantly increase total reproduction which is dispersed into fishing grounds by currents and oceanographic processes. While some offspring may disperse only short distances to resupply a reserve, others may disperse widely to supply more distant fishing grounds. |
Marine reserves are ideally suited to the ecology and life history of most marine organisms with fairly sedentary adults that don't move long distances and juveniles that disperse broadly. Although fishermen must give up some fishing areas, they receive net benefits from healthier stocks and more stable and productive fishery. Thus, the environment wins from increased protection of ecosystem structure and function while people win from enhanced ecosystem goods and services. Increased evidence shows ecosystem and fishery benefits of marine reserves. Studies on small Philippine coral reefs have shown that closing 20 percent of the reef area resulted in an overall 50 percent increase in total catch. Most fishermen would probably consider that a good tradeoff. |
Marine reserves are also critical for scientific understanding of marine ecosystems by providing minimally disturbed areas for research and education. Reserves act to provide important scientific controls for understanding natural processes and measuring human impacts on marine ecosystems. |
Stealth reserve
One test of marine reserve theory is provided by 40 km2 of closed area established in the Merritt Island National Wildlife Refuge starting in 1962 to provide security for the Kennedy Space Center at Cape Canaveral, Florida. This is the oldest, and until 1999 the largest no-take reserve in North America. I call it the "stealth reserve" because and the public and even science was not aware of changes until after the Challenger disaster in 1987 when launching operations were suspended for several years and aquatic scientists were first allowed to do research in the area. |
Johnson et al. (1999) compared three areas protected from all fishing in highly protected security zones with three adjacent areas open to fishing. As predicted by marine reserve theory, exploited species were larger and more abundant in reserves and average fish species diversity per sample was twice as high in the protected areas. Standardized catch per unit effort were 12.8 time greater for Black Drum (Pogonias cromis), 6.3 times grater for Red Drum (Scianops ocellatus), 5.3 time greater for Common Snook (Centropomus undecimalis) and 2.3 times greater for Spotted Sea Trout (Cynoscion nebulosus) in reserves than in similar adjacent fished areas. These densities show a remarkable recovery since we know that the Canaveral area was historically intensively fished. Anderson and Gehringer (1965) showed that about 4 million pounds of fish were landed annually from the area in a study conducted from 1959-1962, before areas were closed. Two thirds of the landings for Spotted Sea Trout, the largest fishery, were made by sport fishermen. |
I tested predictions of marine reserve theory using International Game Fish Association (IGFA) world records as data for the three long-lived species of gamefish that are permanent residents in the area. These data were collected by recreational fishermen under very strict IGFA rules. As reported in Roberts et al. (2001), the total number of world records increased dramatically within 100 km of the closed areas after areas were closed to fishing, accounting for 62 percent of all Florida world records for Black Drum, 54 percent for Red Drum, and 50 percent for Spotted Sea Trout. World records for Common Snook did not show significant increases near Canaveral, but they were not even reported as present in the early 1960s by Anderson and Gehringer (1965). By the 1980s they had established populations in areas closed to fishing. |
Although areas at the Cape were closed for security purposes and not for any fishery purpose, the data clearly show significant benefits to the recreational trophy fishery and support the predictions of the marine reserves model. Although total landings data are not available, the presence and abundance of large fish can be assumed to reflect healthy populations. Other possibilities suggested to account for these data are not consistent with the timing or spatial concentration of world records (Roberts et al.). The results are ironic because the data show direct benefits to recreational fishing, yet recreational fishermen seem to be the most vocal opponents to establishing reserves. |
This article was developed under the auspices of the National Marine Fisheries Service, National Oceanic and Atmospheric Administration, U.S. Department of Commerce. The U.S. Government or any member of the public is authorized to produce and distribute reprints for governmental purposes notwithstanding any copyright notation that may appear hereon. |
|
| |
