Gear Conservation Engineering -- Bycatch

Defining the word bycatch is not as easy as one would think. Bycatch means different things to different people and there is no universally accepted definition of the term "bycatch." In its broadest definition, bycatch is simply regarded as unintended fisheries catch (NOAA 1997). It has also been defined as the harvest of fish or shellfish other than the species for which the fishing gear was set (Wallace and Fletcher 2000). The reauthorized Magnuson-Stevens Fishery Conservation and Management Act (MSA) defines the term "bycatch" as "fish which are harvested in a fishery, but which are not sold or kept for personal use, and includes economic discards and regulatory discards." Such term does not include fish released alive under a recreational catch and release fishery management program.

Now that we have defined bycatch, the next big question, is what causes bycatch? These are as varied as its definition. The fish capture method is not perfect. Some bycatch may result from the limited selectivity of certain fishing gear. Another cause of bycatch is the actual behavior and distribution of the animals which results in a mixture of species. Each of these species may be subject to a specific regulatory regime (e.g. minimum size, net mesh size restriction, trip limits, and area closures) and this array of regulations may lead to discarding. Finally,the regulatory system itself causes bycatch. Management programs have the potential to generate bycatch, therefore, bycatch may be the outcome of the need to regulate fisheries. For example, a quota system may result fish being discarded.

There are a variety of types of bycatch. They can be categorized as regulatory discards and economic discards. Regulatory discards as defined in the MSA are fish harvested in a fishery which fishermen are required by regulation to discard whenever caught, or are required by regulation to retain but not sell (MSA 1996).

The species caught may be below legal size or in excess of established bycatch or catch quotas. Economic discards as defined in the MSA as fish which are the target of a fishery but which are not retained because they are of an undesirable size, sex, or quality, or for other economic reasons (MSA 1996).

Depending on the type of fishery and location, other types of bycatch may also include:

For more information, please visit NOAA Fisheries Feature: Bycatch at http://www.nmfs.noaa.gov/bycatch.htm.