Metrics

This indicator measures the fraction of caught fish that are discarded by fishing vessels, by species.

Analysis

Discarding is the practice of returning catch back to the sea before it is taken to shore. Because most discarded fish do not survive, discarding is widely viewed as a wasteful practice.

Discarding occurs for two main reasons:

1. Regulations may require that fishing vessels discard catch in some circumstances. For example, if fishery regulations cap the total amount of a fish species that can be landed on each fishing trip, any amount of catch that exceeds that cap must be discarded.
2. Fishing operators may choose to discard some fish species or size ranges of catch that have low economic value.

In the U.S. West Coast fishery, the shift to catch shares potentially affected both of those causes of discards. Prior to catch shares, the fishery had “trip limits” on catch of individual species. Under the catch share program, there is no limit on catch on each trip, but rather operators have an annual catch limit (quota) that can be spread out over many trips. Thus, discards caused by high catches on individual trips should be reduced. Additionally, since catch shares reduce the race to fish, fishing operators might be more able to reduce the catch of low-value fish by selectively fishing at locations and times to avoid those fish. Both of these factors are expected to lower the amount of discarding in this fishery.

The overall gross discard fraction—the proportion (by weight) of captured fish that was discarded—declined substantially after catch shares were implemented (Chart 1). Prior to catch shares, between 20% and 45% of annual catch was discarded, whereas after catch shares this rate was reduced to 10% or less. Although there was a clear declining trend in gross discard fraction throughout the early 2000s (declining from a peak of 45% in 2002 to 22% in 2010) before the catch share program, the drop in discards following catch share implementation was sharp and much steeper than the prevailing trend.

There were two main causes for this abrupt drop. First, the total amount of catch (and discarded catch) of species that contributed the most discard tonnage (Pacific hake, arrowtooth flounder, spiny dogfish) declined sharply in 2011 onwards. In other words, total catch of species with high discard ratios declined after the catch share program began. Second, the ratio of discard to catch for many species dropped once the catch share program was implemented. Several rockfish species showed the sharpest and clearest declines immediately with the onset of the catch share program, while some other species such as Dover sole and petrale sole also had sizable declines. Many of the rockfish species are those that had relatively small quotas (and in one case, cowcod, landings were prohibited in California state waters prior to catch shares) during the baseline and catch share period. In total, 11 of the 26 stocks had highly significant declines, and another 6 stocks had moderately significant declines in discard ratios. Across all stocks, the estimated average decline in discard ratio was 40%.

Clearly not all of the reduction in discarding can be attributed to the catch share program. For many species, the ratio of discard to catch declined throughout the baseline period before catch shares were implemented. For instance, Dover sole discard rate declined from 13% to nearly zero from 2006 to 2012. Similarly, lingcod discard rate declined substantially from 2005 to 2012. Patterns in discards like these may be driven by gear technology, market demand, other fishing regulations such as spatial management, and/or a recruitment event bringing a higher-than-usual proportion of small and unmarketable fish into the fishery.