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Have discarding practices changed?

Indicators: Discards | Bycatch

Short Answer: Yes, but the changes do not appear to be attributable to the catch share program. 

Key Findings

  • The percentage of the catch (by weight) that was discarded decreased in the first five years of the catch share program compared to the baseline period.
  • The main reason for the overall decrease in discarding was a decline in discards of Atlantic cod and yellowtail flounder, resulting from a scarcity of young, undersized fish of both species that would have needed to be discarded.
  • Several other species, such as wolffish and Atlantic halibut, were discarded at higher rates in the first five years of the catch share program.

Interactive Chart Story


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

In Their Own Words

Although some of the quantitative data analyzed for this indicator exhibited clear trends, it was challenging to discuss the relationships between observed data trends and implementation of the respective catch share programs, especially in the Northeast. The Measuring the Effects of Catch Shares project team believed that those stakeholders most involved in the fishery, either as active participants or as representatives of an involved coalition of participants (e.g., sector managers in the Northeast), would be able to provide insight and help to explain trends seen in the existing quantitative data. The following quotes were selected to illustrate some of those perspectives and highlight trends such as effects on small vessels, the effect of avoiding “choke stocks,” fleet diversification, and product quality. The individual quotes do not represent findings or conclusions for this indicator, nor do they represent a consensus across any category of participants.

“These other guys, they’ll throw choke species fish overboard all day long. And they’ll sleep just as good that night, as if they’ve done nothing. And that’s the bottom line.”
~ Fishermen

“So with the pressures on fishermen to try and survive, to try to remain fishermen, to try to remain groundfish fishermen, I think it’s safe to assume that there is a lot of catch that we are not accounting for. That’s another perilous part of this whole catch share program. With catch that’s not being accounted for, what do you get? You get errors in the assessments.”
~ Government


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.

Data Gaps, Limitations and Methods

We used observer data from the Northeast Fisheries Observer Program (2002–2014) and the At-Sea Monitors Program (2010–2014). Catch data and catch disposition were aggregated by gear type, vessel size, location, fishing year, and season. Data for this analysis were restricted to bottom trawl and gill net gear, as the vast majority of observed trips were from these gear types. Top discard species were determined by the set of species that in aggregate constituted 95 percent of all observed discards. These species were (in decreasing order) little skate, big skate, spiny dogfish, barndoor skate, Atlantic cod, haddock, windowpane flounder, summer flounder, thorny skate, yellowtail flounder, monkfish, and smooth skate. Statistical analysis identified species with significant declines in discard percentage. Strong evidence of a decline or increase was identified where the analysis indicated 97.5 percent probability of change from baseline to catch share time periods. Moderate evidence was based on a 90 percent probability of change.

Note that the data included in this analysis include only those sets and hauls that were documented by at-sea observers, which represent only a fraction of all sets and hauls in the fishery. We made no attempt to extrapolate discards to all vessels based location, timing, and gears.

Recently, the National Marine Fisheries Service (NMFS) identified discrepancies between stock-area apportioning of catch as reported on vessel trip reports and that as estimated by vessel monitoring system data; the latter provides an approximation of the spatial distribution of fishing effort according to vessel speed. The differences were most pronounced starting in 2010 with implementation of the catch share program, when incentives for misreporting discards of some allocated stocks increased. NMFS found that the overall error was small and unlikely to substantially impact resource monitoring; however, for some stocks (Eastern Georges Bank and Gulf of Maine cod, Gulf of Maine haddock, Southern New England/Mid-Atlantic winter flounder) the estimated errors were large in one or more years. The errors from unreported discards were disproportionately attributed to a small number of vessels and could be reduced with improved catch monitoring.

Information Sources

Data based on Northeast Fisheries Observer Program reports.

Updated: August 2018

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