Course: BIS 105 Environmental Biology

Unit 11 Learning Module

Fisheries

Marine Fisheries

Fisheries are classic common-pool resources. The details of the legal institutions that govern access to fisheries vary around the globe. However, the physical nature of marine fisheries makes them prone to overexploitation. Anyone with a boat and some gear can enter the ocean. One boat’s catch reduces the fish available to all the other boats and reduces the stock available to reproduce and sustain the stock available in the following year. Economic theory predicts that the market failure associated with open access to a fishery will yield socially excessive levels of entry into the fishery (too many boats) and annual catch (too many fish caught) and inefficiently low stocks of fish (Beddington, Agnew, & Clark, 2007).

Visit http://www.nmfs.noaa.gov/sfa/statusoffisheries/SOSmain.htm for updated information on fish stocks

Unfortunately, the state of fisheries around the globe seems to indicate that the predictions of that theory are being borne out and overfishing poses the greatest threat to marine ecosystems. Bluefin tuna are in danger of extinction. Stocks of fish in once-abundant fisheries such as North Atlantic cod and Mediterranean swordfish have been depleted to commercial (and sometimes biological) exhaustion (Montaigne, 2007).

The decline of cod in the North Atlantic.

Harmful Methods

Many desirable species, such as cod and shrimp, are benthic species, meaning they live on the bottom of the ocean. One method of harvesting these species is to use a bottom trawl. This involves dragging a large net that is weighted down with heavy metal plates that keep the net open. This dragging creates a number of environmental problems. First, it damages the structure of the benthic habitat and destroys many of the deep water corals. These slow growing species can be hundreds or even thousands of years old. Secondly, the nets are not very specific for a given species. This results in non-target species being caught and dragged in the net, and then brought to the surface. These non-target species are known as bycatch. Shrimp trawling in particular often has very high bycatch rates, as much as 90% of a trawl load may be bycatch. The bycatch is just discarded overboard, with most of the individuals already being dead. The Gulf of Mexico shrimp fishery catches roughly 45 million pounds of red snapper a year as bycatch, nearly half of what is allotted for the commercial fishery.

Third, the dragging trawl stirs up large amounts of sediments in the water column. These plumes can drift several miles and even be observed with satellites.

In addition, these disturbed sediments may contain hazardous pollutants, thereby increasing the concentration in the water column. Phosphorus is often found in the sediments and may contribute to harmful algae blooms or dead zones after being disturbed.

Longlining is another harmful harvesting technique. A long mainline has thousands of baited hooks which may be fished near the surface when targeting species such as tuna or swordfish, or be fished along the bottom for cod and halibut. One of the major problems is the incidental catching of seabirds, turtles, and sharks. Many types of albatross are threatened or endangered, and longline fishing kills an estimated 100,000 albatross a year.

Early efforts to control overfishing used several kinds of regulations on quotas, fishing effort, and gear. For example, fishing boats are forbidden in some places from using conventional longlines because that gear yields high levels of bycatch and kills endangered leatherback turtles. Some forms of fishery management limit the number of fish that can be caught in an entire fishery. Under a total allowable catch (TAC) system, fishers can fish when and how they want, but once the quota for the fishery has been met, fishing must stop until the next season. Unfortunately, TAC policies do not solve the underlying problem that fishermen compete for the fish, and often yield perverse incentives and undesirable outcomes such as overcapitalization of the industry and races between fishing boat crews to catch fish before the quota is reached. In the well-known case of the Alaskan halibut fishery, the race became so extreme that the fishing season was reduced to a single 24-hour mad dash; given that fish are perishable, this temporal clumping of the catch is not a desirable outcome.

Resource economists developed the idea of a tradable permit scheme to help manage fisheries. Individual tradable quota (ITQ) schemes are cap-and-trade policies for fish, where total catch is limited but fishers in the fishery are given permits that guarantee them a right to a share of that catch. Players in the fishery can sell their quota shares to each other (helping the catch to flow voluntarily to the most efficient boats in the industry) and there is no incentive for captains to buy excessively large boats or fish too rapidly to beat the other boats to the catch. ITQ policies have rationalized the Alaskan halibut fishery completely: the fish stock is thriving, overcapitalization is gone, and the fish catch is spread out over time (Levy, 2010). ITQs have also been implemented in the fisheries of New Zealand, yielding large improvements in the biological status of the stocks. There is some general evidence that ITQ systems have been relatively successful in improving fishery outcomes, though other research implies that evidence of the superiority of the ITQ approach is more mixed. Scholars and fishery managers continue to work to identify the details of ITQ management that make such systems work most effectively, and to identify what needs to be done to promote more widespread adoption of good fishery management policy worldwide.

Marine Protected Areas

Marine Protected Areas (MPAs) are regions of the ocean where natural resources are protected and fishing is either restricted or banned. Most MPAs allow some use and extraction of the resources present with less than 1% of U.S. waters classified as no-take areas. Currently, only 1% of the ocean is protected with such designations. Historically there were areas of the ocean that remained unharvested due to easier capture in other locations or technology limitations, in effect acting as protected areas. However, with today's technological advances and increased fishing efforts there remains virtually no area of the ocean that is off limits.

Because fishing and other extractive activities are limited or not allowed in an area, they often have greater biomass, density, and diversity than areas that are not protected. Fish tend to grow larger in these areas as well, which is important since larger fish often produce much larger quantities of offspring. For example, a single 24" vermillion rockfish produces more eggs than 17 fish that are 14" long. MPAs also act to reseed areas outside of the protected region. This effect, termed spillover, is the result of individuals (as well as eggs and larvae) leaving the protected are to inhabit other suitable locations where they are able to reestablish and potentially be harvested.

This was confirmed in a 2010 study by researchers from Oregon State University looking at yellow tangs around Hawaii. The yellow tang is a commercially important species for the aquarium trade. Due to this pressure, the stocks of yellow tang were at risk of collapsing so 9 MPAs were formed off the coast of Hawaii. Once the larval stage finds a suitable reef, it does not migrate long distances and typically lives in a home range of roughly a half mile in diameter. Therefore, if this species is going to move a long distance it will occur during the larval stage. The researchers examined the DNA and matched the juveniles to where their parents were from and found some had originated from locations as much as 114 miles away, supporting the idea of MPAs acting to replenish fished areas.

One of the largest MPAs in the world is Papahānaumokuākea Marine National Monument. Formerly known as the Northwestern Hawaiian Islands Marine National Monument, it was established by President Bush in 2006. Covering an area of 140,000 square miles, it is approximately the size of Germany, and bigger than all the U.S. National Parks combined.

To view a map of all the U.S. Marine Protected Areas visit http://www.mpa.gov/dataanalysis/mpainventory/mpaviewer/.