Fishery discards in the irish sea exhibit temporal oscillations and trends reflecting underlying processes at an annual scale

Non-inclusion of discard data in stock assessment can lead to underestimation of biomass and fishing mortality; this is of particular concern if there have been changes in discard practices over time. Although variability in space and time is a well-documented feature of discards, the temporal dynam...

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Bibliographic Details
Published in:ICES Journal of Marine Science
Main Authors: Viana, M., Graham, N., Wilson, J. G., Jackson, A. L.
Format: Article in Journal/Newspaper
Language:unknown
Published: Oxford University Press (OUP) 2010
Subjects:
bayesian inference
discards
harmonic regression
time-series
trend
modeling framework
stock assessment
atlantic
ireland
catch
cod
Gadus morhua
Online Access:http://hdl.handle.net/10379/14312
https://doi.org/10.1093/icesjms/fsq160
Description
Summary:Non-inclusion of discard data in stock assessment can lead to underestimation of biomass and fishing mortality; this is of particular concern if there have been changes in discard practices over time. Although variability in space and time is a well-documented feature of discards, the temporal dynamics of the practice has received little detailed attention. The aim here is to characterize the temporal patterns of discarding practices in the Irish Sea (ICES Division VIIa) from 1994 to 2008. Trend and seasonality were explored in discards per unit effort (dpue) of haddock (Melanogrammus aeglefinus), whiting (Merlangius merlangus), and cod (Gadus morhua) through Bayesian harmonic regression (HREG) models. The HREG models reveal discarding of all three species in annual cycles, with a peak in the second quarter, perhaps reflecting species biology or fisher behaviour, or both. The dpue of cod cycled around a constant level throughout the observation period, but whiting and haddock dpue increased.

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