The subject of wastage in fisheries has generated a whole host of words that have different meanings in different contexts and in different parts of the world. One word that is used extensively and causes most confusion is bycatch. As Alverson et al (1994) point out there are at least three accepted definitions of the word. In some circles bycatch is used to refer to catch which is retained and sold but which is not the target species for the fishery. In others (particularly the Northeast and Western Pacific and in American legislation) bycatch means species/sizes/sexes of fish which are discarded (Hall 1996) and in other circles bycatch is used to mean all non-target fish whether retained and sold or discarded. The OECD (1997a) define bycatch as "Total fishing mortality excluding that accounted directly by the retained catch of target species". This definition thus includes fish which die as a result of interaction with the fishing gear, even if they do not leave the water and could include fish which die as a result of "ghost fishing" - capture of fish in the water by lost or abandoned fishing gear.
This confusion can lead to misinterpretation of information provided in scientific and management discussions and can lead to difficulties of interpretation of what is wasted and what is not wasted in the world fisheries scene. These definitions can also rely on the ability to identify what is meant by a target species or group of species. Identification of a target species may be relatively simple in a single or few species fishery with a static marketing base, but in a multi-species fishery and/or when market forces play a significant part in commercial decisions there may be many species in the target and/or the target may change form day to day or even during a fishing operation in a volatile market situation. One days waste and nuisance catch can be tomorrows target. Changes and differences in consumer tastes and marketing opportunities can also influence what is deemed to be waste and what is desirable over a longer time frame and from region to region. For instance the multi-million dollar tropical prawn capture fisheries and the specialised fisheries for Nephrops norvegicus are based on species which were once considered worthless; tropical Penaeid prawns were once thrown over the side by small scale fishermen in many less developed countries, they now form the basis of large industries; monkfish, once considered a nuisance fish is now a sought after and marketable commodity; megrim, witch and dabs, once caught as bycatch in the Icelandic Nephrops fishery are now the subject of target fisheries in Iceland.
The meeting held in Tokyo in October/November 1996 on the reduction of wastage in Fisheries (FAO 1996) concluded that bycatch can best be used as a generic term, applying to that part of the catch made up of non-target species or species assemblages but, when dealing with a specific portion of the catch, in fisheries management terms, it is better to give a more precise definition. The TOTAL CATCH is that quantity taken by the fishing gear and which reaches the deck of the fishing vessel. DISCARDS is that portion thrown away at sea (for one reason or another). The remainder is the LANDED CATCH or RETAINED CATCH (i.e. that which is brought ashore) which can be further sub-divided into TARGET CATCH and INCIDENTAL CATCH, bearing in mind the volume, value, the incidence of species caught and the nature of the fishing operations. The same species can move from one category to another depending on size, market demand, season or other criteria; at the same time other species may be undesirable or of limited value.
In the context of this paper bycatch will be used to refer to that part of the catch which is not the primary target of the fishing effort. It consists of both fish which is retained and marketed (incidental catch) and that which is discarded or released.
In the context of international fisheries statistics it should be noted that while the sum of target and incidental catches (landed or retained catch) are recorded, discards and other fishing induced fishing mortalities, are not. This can be illustrated by reference to the diagram in figure 1 which is taken from the FAO Yearbook of Fishery Statistics Volume 78 (FAO 1996b). Although the terms used in the figure are not precisely the same as those referred to above, the ambiguous term "bycatch" is not used and the definition of discards/discarded catch is the same. It can be seen that
the diagram also divides discarded catch into live and dead. It is the dead discarded catch which is the subject for analysis in this report. There are other sources of unrecorded catch identified in the figure such as that consumed by the crew and fish sold through a black market. These types of lost data do not necessarily, however, imply a loss of fish protein into the human food chain. There may of course be financial losses to a fishing enterprise or loss of the accuracy of data for assessing sound fisheries management strategies through these practices.
However it must be remembered that discarding unwanted fish at sea is not the only cause of non-utilised biomass harvested from the sea. Queirolo et al (1995) suggest, for instance, that offal produced from the processing at sea of ground fish in the Gulf of Alaska and Bering Sea/Aleutian Islands groundfish fishery weighs more than four times the weight of whole fish discarded from the fishery.
There are also of course many instances where fish are marketed but at less than optimal efficiency. For instance where fish at less than the size suitable for the human consumption market is caught, it may be thrown away and constitute part of the discards but, alternatively it may be converted into fish meal. From a utilisation point of view this is a potential under-use of the resource, because of the loss of nutritional value to the intended end user (man) of passing the fish protein it represents through a longer food chain. If the alternative would have been to discard the fish DEAD into the sea then the argument would be that it is better to use the already dead fish for feeding livestock to feed humans than to feed other sea life, however if the fish could have been released ALIVE back into the sea then perhaps allowing it to be harvested later directly as a human food would be better. The interactions between bycatch/discards and arguments for and against reduction are dealt with in some detail by Hall 1996. Fish may also of course be used for the making products outside the human food chain such as pet foods, fertilisers and numerous speciality products which may use part of the fish. There are also of course large quantities of fish wasted because of inadequate post-harvest infrastructure to ensure that is gets to market in edible condition having spoilt before they do so.