Ministry of Agriculture, Fisheries and Food, Directorate of Fisheries Research
Fisheries Laboratory, Pakefield Road, Lowestoft, Suffolk NR33 0HT, U.K.
Source - Journal of Northwest Atlantic Fishery Science, Volume 19: 91-102
A model is described to predict the numbers-at-age of fish discarded in fisheries for which only landings-at-age are known. The model assumes a knowledge of the distribution of length within each age group in the population, and uses mesh selection characteristics and an inferred discarding practice, to derive the proportions of each age group discarded and landed. Mesh selectivity and discarding practice, in terms of proportions of the catch discarded and landed, are described using a logistic fit to the proportions of the population entering the net that are caught, discarded and landed. The application of the model is illustrated using data from the mixed demersal fisheries in the Irish Sea, and the effects of including discards in the assessments and on yield-per-recruit are examined. Including discard estimates in the assessment results in increased estimates of stock numbers and increased fishing mortality on age groups that were subject to discarding. As a result the perceived level of exploitation relative to Fmax was altered.
Language - English
Publisher - Northwest Atlantic Fisheries Organization (NAFO), Dartmouth, N.S., Canada
Publication Date - September 1996
Publication Type - Journal Article