Discarding by Shetland’s Whitefish Vessels: Data from the SFA’s Discards Tally Books

Discard tally sheets were used by the Shetland Fishermen’s Association to collect information from a sample of Shetland’s whitefish vessels on the nature and magnitude of their discards. Eight vessels completed tally sheets over varying periods between June 2013 and July 2014. Completed sheets covered 422 days of fishing and 1,513 tows, during which about 46,000 boxes of fish of more than 24 different species were caught.
Overall, 41% of the recorded catch was discarded. Discards of at least 16 different species were recorded, but hake, cod and saithe accounted for the vast majority of the fish discarded (86%).
Discard rates varied widely between individual species. Of the main species caught hake had the highest discard rate (90%), followed by cod (49%) and saithe (43%). Other commercially important species, such as whiting, haddock, monks and most flatfish had relatively low discard rates (below 5%) and a few species were never discarded. A number of non-target bycatch species also had very high discard rates, although they were caught in relatively small quantities.
There was no clear evidence of any seasonal patterns in discards of the main species, except perhaps a decline in cod discarding towards the end of the year. There was some evidence of differences between seine netters and trawlers in the discard rates of some species (such as saithe and plaice), but discard rates for some other species (such as hake and haddock) were consistent across all fishing gear types.
Discards were recorded from virtually all catches (98%), although the frequency of discarding varied between species. Hake was the most frequently discarded of the main species caught (98% of catches), followed by cod (76%) and saithe (72%).