Metrics

We considered three dimensions to fishing effort: total number of fishing vessels operating in the fleet, total amount of tows, and spatial location by effort.

Analysis

In general, transitions to catch shares in other fisheries have led to reduced fishing effort (sometimes by reduction in fleet size), and also the locations and the times when fishing occurs. Indeed, our work has shown this to be true for the West Coast Groundfish fishery. In addition to overall effort shifts, we also sought to determine whether fishing practices have changed. Under the Shorebased Individual Fishing Quota (IFQ) Program, individuals bear the responsibility of ensuring catches are within catch limits (Ratio of Catch to Quota). The risk of exceeding catch limits, particularly for species with low quota (Annual Catch Limits), might be associated with spatial or seasonal shifts to avoid low quota species.

Baseline: Before Catch Share Program

In the baseline period, the fleet of active, non-whiting vessels averaged 94 vessels per year. There was a consistent decline each year of the baseline period from the highest value (102) in 2005 to the lowest value (88) in 2010 (Total Number of Active Vessels). An average 14,987 tows were conducted each year during the baseline period; unlike number of vessels, there was no consistent decrease. In fact, the greatest amount of effort (17,554 tows) occurred in 2009, although in 2010, the final year of the baseline period, the lowest effort (8,160 tows) was observed. During the baseline period, fishing effort ranged from northern Washington state southward to Santa Cruz, CA. Several distinct hot spots of fishing effort are visible during the period. These include fishing locations offshore in northern Washington, southern Washington / Northern Oregon, near Coos Bay, OR, and Eureka, CA.

During Catch Share Program

Fishing effort was much lower after the implementation of the catch share program. The number of fishing vessels dropped by 17 percent to an annual average of 78 vessels per year. The first year of the catch share program, 2011, saw a 7 percent drop in vessel number compared to the previous year. This drop was maintained or even expanded in subsequent years, reaching a low of 71 vessels in 2015, the final year for which we have data. The number of trawl tows continually decreased during catch share program years, with a reduction of 32 percent in the first year of the catch share program. The average annual number of tows (8,976 tows per year) was about 40 percent less than the average during the baseline period. The number of tows in 2014 was half of the peak value seen in the baseline period.

The reduction in fishing effort was experienced uniformly along the coast. The largest reductions were experienced in central Oregon and central California. Compared with the baseline period, there was a shift in effort to nearshore fishing locations along Washington and northern Oregon during the catch share program years. Spatial area fished contracted by 35 percent overall. However, no new hotspots of fishing activity were apparent, and the main areas of fishing activity during the baseline period continued to be commonly fished areas during the catch share program years.

It is likely that the spatial shifts reflect, in part, fishermen’s attempts to catch target species while avoiding quota-constraining (overfished) species. Under the Shorebased IFQ Program, discarded catch counts against individual quota, as opposed to the previous management regime that permitted vessels to discard fish at sea without individual penalty for quota overages. We have demonstrated that the fleet has largely been successful at catching quota for valuable species while avoiding catches of overfished species (Ratio of Catch to Quota; Kuriyama et al., 2016).

Methods

Data Processing
For most of our analyses, we combined two data sources: logbook data (2007–2010) and observer data (2007–2014). For each tow, both data sources contained the latitude, longitude, and depth at which nets entered and exited the water. Catch compositions were reported by species, although the logbook data did not include discard amounts, whereas observer data did. Observers monitored roughly 20 percent of trips prior to 2011, after which observer coverage increased to 100 percent of trips (Pacific Fishery Management Council and NMFS, 2010). From 2007 to 2010, we therefore preferred observer records when tows were recorded in both the logbook and observer data.

Spatial Analyses
We divided the coast into grids to measure the spatial changes in fishing effort over time. We hypothesize that effort will likely decline and concentrate in specific areas of the coast. The grids were based on latitude and depth (0.5° by 91 meters, equivalent to 50 fathoms) because the coastline is fairly straight in a north-south direction, and because in some areas of the coast, movement of a few kilometers east or west can result in depth changes of hundreds of kilometers in the fishery. Tows were assigned to grid cells based on the midpoint between start and end tow locations. To estimate how effort in each grid changed over time, we fitted linear models to the number of tows in each year in each grid cell:

Ntows = aYear + b

We quantified individual vessel movement before and after catch shares. Vessels that did not remain in the fishery after catch shares and vessels that had shifts greater than one degree of latitude or longitude were not included for this analysis (4 vessels). Shifts in fine-scale effort were quantified by calculating the difference between average latitudes and longitudes for the remaining vessels in the four years before and after catch shares. We used ANOVAs for individual-vessel latitude and longitude to calculate significance in the shifts.

Information Sources

Kuriyama, P.T., T.A. Branch, M.A. Bellman, and K. Rutherford. 2016. Catch shares have not led to catch-quota balancing in two North American multispecies trawl fisheries. Marine Policy 71:60-70. Online: https://www.sciencedirect.com/science/article/pii/S0308597X16302925

Updated: August 2018