Transplant/release captive-bred or hatchery-reared species - Transplant/release crustaceans

How is the evidence assessed?
  • Effectiveness
    70%
  • Certainty
    45%
  • Harms
    0%

Source countries

Key messages

  • Five studies examined the effects of transplanting or releasing hatchery-reared crustacean species on their wild populations. Four examined lobsters in the North Sea (Germany, Norway, UK), and one examined prawns in the Swan-Canning Estuary (Australia).

 

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (5 STUDIES)

  • Crustacean abundance (1 study): One study in the Swan-Canning Estuary  found that after releasing hatchery-reared prawn larvae into the wild, the abundance of egg-bearing female prawns increased.
  • Crustacean reproductive success (3 studies): Two studies (one controlled) in the North Sea found that after their release, recaptured hatchery-reared female lobsters carried eggs, and the number, size and developmental stage of eggs were similar to that of wild females. One study in the Swan-Canning Estuary  found that after releasing hatchery-reared prawn larvae into the wild the overall population fecundity (egg production/area) increased.
  • Crustacean survival (2 studies): Two studies in the North Sea found that 50–84% and 32–39% of hatchery-reared lobsters survived in the wild after release, up to eight and up to five years, respectively.
  • Crustacean condition (4 studies): Two studies in the North Sea found that hatchery-reared lobsters grew in the wild after release. One controlled study in the North Sea found that after release into the wild, hatchery-reared female lobsters had similar growth rates as wild females. One study in the North Sea found that after releasing hatchery-reared lobsters, no recaptured lobsters displayed signs of “Black Spot” disease, and 95% had developed a crusher-claw. One study in the Swan-Canning Estuary  found that after releasing hatchery-reared prawn larvae into the wild, the size of egg-bearing female prawns increased.

BEHAVIOUR (1 STUDY)

  • Crustacean movement (1 study): One controlled study in the North Sea found that after release into the wild, hatchery-reared female lobsters had similar movement patterns as wild females.

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 1983–1992 in one seabed area off the east coast of England, North Sea, UK (Bannister et al. 1994) estimated that between 50–84% of the initial number of released hatchery-reared European lobsters Homarus gammarus survived and increased in size for up to eight years in the wild. Lobsters recaught reached 85 mm (legal catch size) within four to eight years after release. Between 1983 and 1988, hatchery-reared lobsters (49,000 in total) were tagged and released across an area of 30 x 8 km onto cobbles and boulders at 80 locations (10–15 m depth). At time of release, lobsters were three months old with carapaces measuring 15 mm in length. Between 1988 and 1992, a recapture programme caught a total of 56,700 lobsters, of which 621 were tagged lobsters previously released. The carapaces of recaptured tagged lobsters were measured. It is not known if the number of uncaught tagged lobsters was due to mortality or recapture effort. Percentage survival of the 49,000 released lobsters was estimated from the recapture programme catch-rate data.

    Study and other actions tested
  2. A controlled study in 1998–2000 in one area off southwestern Norway, North Sea (Agnalt et al. 2007 - same experimental set up as Agnalt et al. 2008) found that hatchery-reared female European lobsters Homarus gammarus released into the wild had similar growth rate and movement patterns, compared to wild females. Regardless of carapace length, the growth rate of hatchery-reared females (7–10 mm between moults) was similar to that of wild females (3–8 mm). In total, 53% of hatchery-reared females remained within 500 m of their release sites, which was similar to wild females (41%). Between 1990 and 1994, hatchery-reared juvenile lobsters (approximately 128,000) were released as part of a restocking program. During the fishing season each year from 1998 to 2000, egg-bearing female lobsters caught by fishers were measured (total length, carapace length), weighed, and hatchery-reared females were differentiated from wild females by the presence of tags. All females were then retagged, kept in holding pens in the sea, and released after the end of the fishing season to potentially be recaptured by fishers the following fishing season (mark-recapture). A total of 81 hatchery-reared females and 231 wild females were recaptured at least once. Locations of release and recapture sites were recorded.

    Study and other actions tested
  3. A controlled study in 1996–1997 in one seabed area off southwestern Norway, North Sea (Agnalt et al. 2008 - same experimental set up as Agnalt et al. 2007) found that when comparing individuals of similar sizes, female hatchery-reared European lobsters Homarus gammarus released into the wild carried similar numbers of eggs and their eggs were of similar weight, diameter, and developmental stage, compared to wild lobsters. For further details of results see graphs in paper. Between 1990 and 1994, hatchery-reared juvenile lobsters (approximately 128,000) were released as part of a restocking program. During autumn 1996, and spring and autumn 1997, egg-bearing female lobsters were collected from commercial landings. Hatchery-reared females (104 individuals) were differentiated from wild females (111 individuals) by the presence of tags. All female lobsters were measured (carapace length), and the weight of their egg mass recorded. For each female, egg count and size were assessed from subsamples. A note was made of any developing embryos.

    Study and other actions tested
  4. A study in 2000–2009 in one area of rocky seabed off Helgoland, German Bight, North Sea (Schmalenbach et al. 2011) found that after releasing one-year-old hatchery-reared European lobsters Homarus gammarus, they grew and survived in the wild, became reproductive, and appeared healthy. Recaptured lobsters had grown in the wild (females: 14.5–19.8; males: 16.8–21.8 mm/year) and reached 85 mm (legal catch size) within four to seven years after release. Survival rate of lobsters released in 2000 and 2001 was estimated at 32 and 39% respectively after up to five years. In addition, no recaptured lobsters displayed signs of “Black Spot” disease, 95% had developed a crusher-claw, and 16% of recaptured females carried eggs. Annually in 2000–2005, at two locations of 10 m water depth, tagged hatchery-reared lobsters were released at the surface (5,421 lobsters in total). Released lobsters weighed 1.5 g and had carapaces 15 mm long. Between 2000 and 2009, 488 of these were recaptured at least once, using lobster pots, traps, and divers. It is not known if the number of uncaught tagged lobsters was due to mortality, recapture effort, or migration outside the search zone. Recaptured lobsters were sexed, observed for signs of disease and presence of a crusher-claw, and their carapaces measured. Percentage survival was estimated from the mark-recapture programme data obtained between 2001 and 2005 for the 1,036 released in 2000 and 2001.

    Study and other actions tested
  5. A study in 2013–2016 of 36 sites in the Swan-Canning Estuary, south-western Australia (Crisp et al. 2018) found that during the three years after yearly releases of hatchery-reared western school prawn larvae Metapenaeus dalli the abundance and size of egg-bearing females, as well as the overall population egg production, increased. Abundance of egg-baring females increased from 0.1–0.6/500 m2 in 2013–2014 and 0.6–1.4 in 2014–2015 to 1.1–1.6 in 2015–2016. The carapace length of egg-bearing females increased from 17–20 mm in 2014–2015 to 23-24 mm in 2015–2016. Egg production (fecundity) increased from 16,000 egg/500 m2 in 2013–2014, to 34,000 in 2014–2015 and 163,000 in 2015–2016. However, authors indicate that wild and hatchery-reared prawns could not be discerned, and therefore that the results cannot be solely attributable to the restocking programme. Yearly between December 2012 and March 2016, hatchery-reared juvenile prawns were released into the estuary (15,000 in 2012–2013; 635,000 in 2014–2015; 2 million in 2015–2016) as part of a restocking programme. Monthly in October 2013–March 2016, prawns were collected using a mix of hand nets (9 mm mesh; 570 m2) and otter trawls (9 mm at the codend; 650 m2) at 36 sites (two samples/site/month). Prawns were counted, sized, sexed, and egg-bearing females recorded.

    Study and other actions tested
Please cite as:

Lemasson, A.J., Pettit, L.R., Smith, R.K. & Sutherland, W.J. (2020) Subtidal Benthic Invertebrate Conservation. Pages 635-732 in: W.J. Sutherland, L.V. Dicks, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2020. Open Book Publishers, Cambridge, UK.

Where has this evidence come from?

List of journals searched by synopsis

All the journals searched for all synopses

Subtidal Benthic Invertebrate Conservation

This Action forms part of the Action Synopsis:

Subtidal Benthic Invertebrate Conservation
Subtidal Benthic Invertebrate Conservation

Subtidal Benthic Invertebrate Conservation - Published 2020

What Works in Conservation

What Works in Conservation provides expert assessments of the effectiveness of actions, based on summarised evidence, in synopses. Subjects covered so far include amphibians, birds, terrestrial mammals, forests, peatland and control of freshwater invasive species. More are in progress.

More about What Works in Conservation

Download free PDF or purchase
The Conservation Evidence Journal

The Conservation Evidence Journal

An online, free to publish in, open-access journal publishing results from research and projects that test the effectiveness of conservation actions.

Read the latest volume: Volume 17

Go to the CE Journal

Subscribe to our newsletter

Please add your details if you are interested in receiving updates from the Conservation Evidence team about new papers, synopses and opportunities.

Who uses Conservation Evidence?

Meet some of the evidence champions

Endangered Landscape Programme Red List Champion - Arc Kent Wildlife Trust The Rufford Foundation Save the Frogs - Ghana Bern wood Supporting Conservation Leaders National Biodiversity Network Sustainability Dashboard Frog Life The international journey of Conservation - Oryx British trust for ornithology Cool Farm Alliance UNEP AWFA Butterfly Conservation People trust for endangered species Vincet Wildlife Trust