Limit the number of fishing days
Overall effectiveness category Awaiting assessment
Number of studies: 1
Background information and definitions
Overfishing leads to volumes of fish being caught that are unsustainable, both ecologically and economically, as well as to damage of fish habitats. Restriction of fishing capacity or effort may therefore help to reduce the effects of overfishing. One way to achieve this may be to limit the duration of fishing by capping the number of days that may be spent at sea. However, other measures may also be needed (by limiting the number of licenced vessels, for example) to prevent the same amount of fish being caught in a shorter period by an increased number of vessels, as was reported for Pacific halibut in the late 1980s (Szymkowiak et al. 2020).
Szymkowiak M., Marrinan S. & Kasperski S. (2020) The Pacific Halibut, Hippoglossus stenolepis, and Sablefish, Anoplopoma fimbria, Individual Fishing Quota Program: A Twenty-year Retrospective. Marine Fisheries Review, 82, 1–16.
Supporting evidence from individual studies
A before-and-after study in 1985–2002 of an area of seabed in the Strait of Sicily, Mediterranean Sea, off Italy (Garofalo et al. 2003) reported that following a decrease in the overall number of days fished (or fishing effort) by a bottom trawl fleet there was an increase in biomass of thornback ray Raja clavata and brown ray Raja miraletus. Data were not tested statistically. Total ‘days’ fished decreased to 11,000–12,000 hrs/season in 1997–2002, from 16,000–32,000 hrs/season in 1985–1996. Over the same period (1997–2002) average biomass of thornback ray increased (6.0 to 8.0 kg/km2), as did average biomass of brown ray (3.4 to 5.0 kg/km2) following an earlier decline in 1985–1996 (4.0 down to 3.0 kg/km2). In the late 1980s and early 1990s changes to the Mazara del Vallo trawl fleet in the Strait of Sicily (fewer small coastal vessels to more large trawlers designed for offshore fishing) resulted in a large reduction in fishing effort in overexploited areas, as fishing activity moved to other areas. Ray abundance data were collected during scientific trawl surveys conducted in 1985–86, 1990–91, 1994–98 and 2000–02. The vessel used was a commercial charter that deployed an ‘Italian Bottom Trawl’ of 28 mm codend mesh size. Fishing effort data were derived from Harbour Office records and interviews with fishers.Study and other actions tested