Limit the number of fishing days

Overall effectiveness category Awaiting assessment
Number of studies: 1
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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.

Study locations

Key messages

One study examined the effects of limiting the number of fishing days on marine fish populations. The study was in the Mediterranean Sea (Italy).

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One before-and-after study in the Mediterranean Sea reported that in the 10 years following a decrease in overall number of days fished by a bottom trawl fleet, there was a higher biomass of thornback and brown rays.

BEHAVIOUR (0 STUDIES)

About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

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
Referenced paper
Garofalo G., Gristina M., Fiorentino F., Cigala Fulgosi F., Norrito G. & Sinacori G. (2003) Distributional pattern of rays (Pisces, Rajidae) in the Strait of Sicily in relation to fishing pressure. Hydrobiologia, 503, 245-250.

Please cite as:

Taylor, N., Clarke, L.J., Alliji, K., Barrett, C., McIntyre, R., Smith, R.K., and Sutherland, W.J. (2021) Marine Fish Conservation: Global Evidence for the Effects of Selected Interventions. Synopses of Conservation Evidence Series. University of Cambridge, Cambridge, UK.

Where has this evidence come from?

List of journals searched by synopsis

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This Action forms part of the Action Synopsis:

Marine Fish Conservation

Related Actions

Actions	Effectiveness	Studies	Category
Implement multi-year or long-term management strategies Action Link	Awaiting assessment	1	Synopsis Link
Limit the number of fishing permits/licences to limit vessel or fisher numbers Action Link	Awaiting assessment	0	Synopsis Link
Prohibit certain gear types Action Link	Awaiting assessment	2	Synopsis Link