Protect spawning fish from capture

How is the evidence assessed?
  • Effectiveness
    not assessed
  • Certainty
    not assessed
  • Harms
    not assessed

Study locations

Key messages

  • Four studies examined the effects of protecting spawning fish on marine fish populations. Two studies were in the North Atlantic Ocean (Canada, UK) and one study was in each of the Philippine Sea (Palau) and the Tasman Sea (Australia). 



  • Abundance (1 study): One before-and-after, site comparison study in the Atlantic Ocean found no increase in the biomass of the spawning stock of Atlantic cod in the nine years following implementation of a seasonal fishery closure to protect spawning cod, compared to fished areas.
  • Survival (1 study): One before-and-after, site comparison study in the Atlantic Ocean found no change in Atlantic cod survival in the nine years after a seasonal fishery closure to protect spawning cod was implemented, compared to fished areas.
  • Condition (1 study): One before-and-after, site comparison study in the Atlantic Ocean found no change in the length composition of Atlantic cod in the nine years following a seasonal fishery closure to protect spawning cod, compared to fished areas.



  • Commercial catch abundance (2 studies): One before-and-after, site comparison study in the Atlantic Ocean found no change over nine years in commercial catches of Atlantic cod following a seasonal fishery closure to protect spawning cod compared to fished areas. One replicated, controlled study in the Philippine Sea found that during seasonal closure of a grouper fishery to protect spawning individuals, the commercial catch numbers of other fish groups (herbivores) increased, indicating they were being targeted more by spear fishers compared to the open season.

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

  1. A study in 2007–2012 of a seabed area in the Gulf of St. Lawrence, Northeast Atlantic Ocean, Canada (Le Bris et al. 2013) found that tagged adult Atlantic cod Gadus morhua showed frequent and long-term use over five years of a seasonally closed area designed to protect a cod spawning aggregation from fishing mortality. These results were not statistically tested. Tagged adult cod spent an average 28% of time (range 0–72%) inside the closed area during its enforcement period and were recaptured after between 224–746 days, indicating long-term survival. Movement patterns of different groups of cod indicated that migratory cod used the area more extensively (13–72%) than non-migratory cod (0%). In addition, 17 tags from the 353 adult cod tagged were returned (i.e. captured; the fate of the other 336 is unknown). A closed area of 5,000 km2 was implemented in 2002 prohibiting all ground fishing activities yearly from April 1st to June 15th. Between 2007–2012, a total of 353 cod were captured using baited handlines and surgically implanted with data storage tags. Of the 17 tags returned, complete data from 14 were used to reconstruct cod movements.

    Study and other actions tested
  2. A replicated, controlled study in 2009 of reef fisheries in the Philippine Sea, Palau, Micronesia (Bejarano Chavarro et al. 2014) found that the implementation of a closed season to protect spawning aggregations of five grouper species Serranidae spp. resulted in higher spear fisher catch rates of other fish species (herbivores) by number but not by weight, compared to the open season, and indicated an increase in the commercial targeting of these species. Average catch numbers of herbivorous fish actively targeted by spear fishers throughout the year were higher during the closed grouper season (7 fish/person/h) than the open season (4 fish/fisher/h), but there was no difference in catch rates by weight (closed: 4, open: 3 kg/fisher/h). For other groups of herbivorous fish (harvested opportunistically or normally avoided), catch rates were higher during the closed season by both number (closed: 2.2, open: 0.6 fish/fisher/h) and weight (closed: 1.6, open: 0.5 kg/fisher/h). Since 1994, a closed season (April–July) for five grouper species was implemented to protect spawning fish. In 2009, daily surveys of reef fish landings were done at Koror fish market for two weeks during the open (18–31st March) and closed (13–26th July) grouper fishing seasons. Nineteen spear fisher catches during the closed season and 23 during the open season were sampled and ranked by category of herbivorous fish based on information given by the fishers: actively targeted (10 species), opportunistically harvested (24 species) and avoided (17 species). Species, weight and length was recorded for parrotfishes Scaridae, surgeonfishes and unicornfishes Acanthuridae and rabbitfishes Siganidae.

    Study and other actions tested
  3. A before-and-after, site comparison study in 1986–2010 of an area of seabed in the north east Atlantic Ocean, western Scotland, UK (Clarke et al. 2015) found that a seasonal fishery closure implemented to protect the spawning of Atlantic cod Gadus morhua resulted in no change in catches, spawning stock biomass, length composition or mortality of cod in the nine years following implementation compared to before and to two fished areas. Data were reported as statistical model results. Catch/unit effort and spawning stock biomass of cod decreased after the seasonal closure was implemented, in both the closed area and two fished areas. The length composition of cod was similar between the closed and fished areas and did not change after the closure. Mortality rates differed between areas before and after the closure and intermediate mortality rates were found in the closed area compared to the two fished areas. Annual seasonal fishery closures from 6th March to 30th April were introduced in the Firth of Clyde in 2001 to protect spawning Atlantic cod. Cod were surveyed in one of two zones of the closure area, both closed to gears that target fish but permitted creeling and scallop dredging. Trawling for Norway lobster Nephrops was allowed in the surveyed zone but not in the adjacent zone (not surveyed). Cod landings and hours fished by vessels over 10 m along the west coast of Scotland were extracted from the Marine Scotland database. Cod data from within the closure and from two fished reference areas were obtained from scientific bottom trawl surveys for the period 1986–2010.

    Study and other actions tested
  4. A site comparison study in 2012–2013 in a coastal bay in the Tasman Sea off Tasmania, Australia (McAllister et al. 2015) found that tagged school sharks Galeorhinus galeus less than one year old were detected more frequently inside than outside a shark spawning and nursery ground in which the taking of sharks was prohibited (shark refuge area), however slightly older immature sharks did not tend to stay within the refuge. These results were not statistically tested. On average, the 31 tagged sharks less than one year old were detected for 80% of time inside the closed refuge area. Of these, 19 sharks did not leave the refuge throughout the study, nine periodically left and returned between May and September 2012 and three left and were not detected again. Older immature sharks (between one and two years) spent on average 18% of time inside the refuge area and all eight individuals left the refuge in autumn and only one returned the following spring. Data were collected from 39 electronically tagged sharks. Shark movements were tracked by 58 receivers deployed in and around a shark refuge area (targeting or taking of sharks prohibited year round, year established not given) and 66 receivers in two areas further up the east coast of Tasmania. Data were recorded from January 2012 until May 2013.

    Study and other actions tested
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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Marine Fish Conservation

This Action forms part of the Action Synopsis:

Marine Fish Conservation
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