Metric

This indicator shows the percentage of caught fish (by weight) that were discarded by fishing vessels, based on data collected by at-sea observers.

Analysis

In many fisheries, fishermen commonly discard at sea some of the fish that they have caught, often in order to adhere to regulatory constraints or because they seek higher-value catches. Because many discarded fish do not survive, discarding is widely viewed as a wasteful practice, and it reduces future catch opportunities by depressing population status.

In general, a transition to catch shares and annual catch limits from days-at-sea management has the potential to affect discard rates in a number of ways. On one hand, the introduction of annual catch limits could lead to an increase in regulatory discards—meaning that fishermen are required to discard catch in order to stay below their quotas—in cases when catches exceed catch limits. On the other hand, increased flexibility with catch shares could allow the fleet to avoid catches of more highly regulated species that would require discarding if caught. Finally, because sector participants have a secured access to quota, they may have stronger incentives to avoid practices that would reduce their catches in the future.

Our analysis of the data indicated that discarding happened at a lower rate after the catch share program began. However, the reductions were due largely to fewer undersized fish in the population and to shifts in the relative abundance of low-valued species. For stocks in the Northeast multispecies fishery, the gross discard percentage—the proportion of caught fish by weight that was discarded—was lower in the first five years of the catch share program than in any year of the baseline period. It was not, however, an across-the-board decrease for all managed species. The decrease resulted mainly from declines in discarding of only two species—Atlantic cod and yellowtail flounder—which had accounted for most of the discards among all managed species. The reductions in discards for cod and yellowtail flounder were likely attributable to the low numbers of young fish in the populations of both species from 2010 to 2014, which meant lower catches of undersized fish that would need to be discarded.

While available information provided evidence that Atlantic cod, plaice, redfish, and yellowtail flounder all were discarded at lower rates from 2010 onward, several other species experienced increases. Most strikingly, wolffish discards increased from less than 10 percent to nearly 100 percent, as the New England Fishery Management Council prohibited retention of this species effective 2010 to enhance stock rebuilding. Similarly, Atlantic halibut discards ranged between 40 and 50 percent prior to catch shares but increased to nearly 70 percent after the implementation of catch shares. As a consequence of these divergent species-level responses, the average discard percentage for all species was greater in the catch share years than the baseline years.

Vessels fishing for groundfish also catch other species that are not managed under the Multispecies Fishery Management Plan, and many of these represent substantial components of catches.  Among the most highly discarded species, there was a steady increase in gross discard percentage from 2010 to 2013, followed by a slight decline. The average discard percentage was relatively stable. The considerable increase in gross discards can be attributed to substantially reduced catches of Atlantic cod from 2009 to 2014. Discard rates for Atlantic cod are generally low (below 20 percent), especially compared to spiny dogfish and skates, which have discard ratios between 70 and 100 percent. The change from catches dominated by Atlantic cod catch to catches dominated by dogfish and skates led to an increase in gross discard percentage. Few of the top species showed evidence for a declining discard percentage. Spiny dogfish had some evidence of a decline, while discards of big skate increased.