Likely to be beneficial

Translocate species - Translocate molluscs

1Nine studies examined the effects of translocating mollusc species on their wild populations. Two examined scallops in the North Atlantic Ocean (USA) and one examined scallops in the Tasman Sea and South Pacific Ocean (New Zealand). One study examined conch in the Florida Keys (USA). One examined clams in the North Atlantic Ocean (Portugal). One examined abalone in the North Pacific Ocean (USA). One examined mussels in Strangford Lough (UK). Two examined mussels in the Gulf of Corinth (Greece).

2COMMUNITY RESPONSE (0 STUDIES)

3POPULATION RESPONSE (8 STUDIES)

4Mollusc abundance (3 studies): One replicated, controlled, before-and-after study in the North Atlantic Ocean found that translocating bay scallops increased larval recruitment into the adult population compared to before translocation. One before-and-after study in the North Pacific Ocean found that following translocation of adult pink abalone to existing patchy populations, total abalone abundance (translocated and resident) decreased to similar levels as before translocation. One replicated, site comparison study in Strangford Lough found that after translocating horse mussels, the abundance of young mussels was higher in site with translocated mussels compared to both sites without translocated mussels and natural mussel reefs.

5Mollusc reproductive success (1 study): One replicated, controlled, before-and-after study in the North Atlantic Ocean found that translocating bay scallops did not increase larval production compared to before translocation. Mollusc survival (5 studies): Three replicated studies (one before-and-after and two site comparisons) in the North Atlantic Ocean and in the Tasman Sea and South Pacific Ocean, found that following translocation, scallops and clams survived. Survival of translocated New Zealand scallops was higher in areas closed to commercial fishing compared to fished areas. Two studies in the Gulf of Corinth found that Mediterranean fan mussels survived when translocated to a deep site, and had similar survival compared to naturally-occurring mussels, but did not survive when translocated to a shallow site. Mollusc condition (2 studies): One replicated, site comparison study in the North Atlantic Ocean found that following translocation, clams had similar condition indices to clams in the source site. One study in the Gulf of Corinth found that translocated Mediterranean fan mussels had similar size-specific growth-rates compared to naturally-occurring mussels.

6BEHAVIOUR (1 STUDY)

7Mollusc behaviour (1 study): One replicated study in the Florida Keys found that translocating non-reproductive adult queen conch to aggregations of reproductive conch did not have adverse effects on the movement patterns of non-translocated resident conch, and all conch displayed similar total distance travelled, movement rates, migration patterns, home-range sizes, and sociability.

8Assessment: likely to be beneficial (effectiveness 60 %; certainty 60 %; harms 10 %).

9https://www.conservationevidence.com/actions/2270

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

10Five 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).

11COMMUNITY RESPONSE (0 STUDIES)

12POPULATION RESPONSE (5 STUDIES)

13Crustacean 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.

14Crustacean 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.

15Crustacean 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.

16Crustacean 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.

17BEHAVIOUR (1 STUDY)

18Crustacean 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.

19Assessment: likely to be beneficial (effectiveness 70 %; certainty 45 %; harms 0 %).

20https://www.conservationevidence.com/actions/2266

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

21Eight studies examined the effects of transplanting or releasing hatchery-reared mollusc species on their wild populations. One examined abalone in the North Pacific Ocean (Canada), one examined clams off the Strait of Singapore (Singapore), one examined oysters in the North Atlantic Ocean (USA), and four examined scallops in the North Atlantic Ocean and Gulf of Mexico (USA).

22COMMUNITY RESPONSE (0 STUDIES)

23POPULATION RESPONSE (8 STUDIES)

24Mollusc abundance (2 studies): One replicated, before-and-after study in the North Atlantic Ocean found that after transplanting hatchery-reared scallops, abundance of juvenile scallops typically increased, but not that of adult scallops. Two replicated, randomized, controlled studies in the North Atlantic Ocean, found that after releasing hatchery-reared oyster larvae, more spat initially settled using a direct technique compared to a traditional remote technique, and equal number of spat settled on cleaned and natural oyster shells.

25Mollusc reproductive success (1 study): One replicated, before-and-after study in the North Atlantic Ocean found that after transplanting hatchery-reared scallops, larval recruitment increased across all areas studied.

26Mollusc survival (5 studies): One replicated study in the Strait of Singapore found that, after transplantation in the field, aquarium-reared clams had a high survival rate. One replicated, controlled study in the North Atlantic Ocean found that after transplanting hatchery-reared scallops, the number of transplanted scallops surviving decreased regardless of the methods used, and maximum mortalities was reported to be 0–1.5 %. One replicated, controlled study in the North Pacific Ocean found that transplanting hatchery-reared abalone into the wild reduced survivorship compared to non-transplanted hatchery-reared abalone kept in tanks. Two replicated, randomized, controlled studies in the North Atlantic Ocean found that after releasing hatchery-reared oyster larvae, 61 % of the settled spat survived the winter, and settled spat survived equally on cleaned and natural oyster shells.

27Mollusc condition (3 studies): Two replicated studies in the Strait of Singapore and the North Atlantic Ocean found after transplantation in the wild, aquarium-reared clams and hatchery-reared scallops increased in weight and/or grew. Scallops grew in both free-planted plots and suspended bags but grew more in free-planted plots. One replicated, before-and-after study in the Gulf of Mexico found that after transplanting hatchery-reared scallops, wild populations had not become genetically more similar to hatchery-reared scallops. One replicated, controlled study in the North Atlantic Ocean found that after transplanting hatchery-reared scallops, free-planted scallops developed less shell biofouling than suspended scallops.

28Assessment: likely to be beneficial (effectiveness 45 %; certainty 40 %; harms 15 %).

29https://www.conservationevidence.com/actions/2267

Unknown effectiveness

Cease or prohibit the harvesting of scallops

30Three studies examined the effects of ceasing or prohibiting the harvesting of scallops on their populations. One study was in the South Atlantic Ocean (Argentina), one in the English Channel (UK) and one in the Irish Sea (UK).

31COMMUNITY RESPONSE (0 STUDIES)

32POPULATION RESPONSE (3 STUDIES)

33Scallop abundance (3 studies): Two of three site comparison studies (one replicated, one before-and-after) in the South Atlantic Ocean, the English Channel, and the Irish Sea found that in areas where scallop harvesting had stopped scallop abundance was similar, and one found that scallop biomass was higher, compared to harvested areas.

34Assessment: unknown effectiveness (effectiveness 45 %; certainty 33 %; harms 0 %).

35https://www.conservationevidence.com/actions/2277

Tag species to prevent illegal fishing or harvesting

36One study examined the effects of tagging species to prevent illegal fishing or harvesting on subtidal benthic invertebrates. The study examined the effects on the Californian abalone fishery (USA).

37COMMUNITY RESPONSE (0 STUDIES)

38POPULATION RESPONSE (0 STUDIES)

39BEHAVIOURS (1 STUDY)

40Behaviour-change (1 study): One before-and-after study in California found no significant reduction in non-compliance with daily quotas of abalones after introducing tagging regulations.

41OTHER (1 STUDY)

42Illegal catch (1 study): One before-and-after study in California found no significant reduction in illegal takes of abalones after introducing tagging regulations.

43Assessment: unknown effectiveness (effectiveness 20 %; certainty 22 %; harms 0 %).

44https://www.conservationevidence.com/actions/2275

Translocate species - Translocate crustaceans

45One study examined the effects of translocating crustacean species on their wild populations. The study took place in the Tasman Sea (Australia).

46COMMUNITY RESPONSE (0 STUDIES)

47POPULATION RESPONSE (1 STUDY)

48Crustacean survival (1 study): One study in the Tasman Sea found that following translocation survival of southern rock lobsters was similar to that of resident lobsters.

49Assessment: unknown effectiveness (effectiveness 75 %; certainty 24 %; harms 0 %).

50https://www.conservationevidence.com/actions/2269

Translocate species - Translocate worms

51One study examined the effects of translocating worm species on their wild populations. The study was in Scottish Lochs (UK).

52COMMUNITY RESPONSE (0 STUDIES)

53POPULATION RESPONSE (1 STUDY)

54Worm survival (1 study): One replicated, controlled study in Scottish Lochs found that no reef-forming red tube worm survived when translocated to a new Loch, but survival was high when worms were translocated back to its source Loch.

55Worm condition (1 study): One replicated, controlled study in Scottish Lochs found that no reef-forming red tube worm survived and so no growth was recorded when translocated to a new loch, worms translocated back to its source Loch grew.

56Assessment: unknown effectiveness (effectiveness 10 %; certainty 25 %; harms 15 %).

57https://www.conservationevidence.com/actions/2271

Transplant/release captive-bred or hatchery-reared species in predator exclusion cages

58One study examined the effects of transplanting or releasing hatchery-reared species in predator exclusion cages on their wild populations. The study was in the North Pacific Ocean (Canada).

59COMMUNITY RESPONSE (0 STUDIES)

60POPULATION RESPONSE (1 STUDY)

61Survival (1 study): One replicated, controlled study the North Pacific Ocean found that hatchery-reared abalone transplanted in predator exclusion cages had similar survivorship following release compared to those transplanted directly onto the seabed.

62Assessment: unknown effectiveness (effectiveness 35 %; certainty 26 %; harms 0 %).

63https://www.conservationevidence.com/actions/2268

No evidence found (no assessment)

64We have captured no evidence for the following interventions:

• Cease or prohibit the harvest of conch
• Cease or prohibit the harvest of sea urchins
• Establish size limitations for the capture of recreational species
• Provide artificial shelters following release
• Remove and relocate invertebrate species before onset of impactful activities
• Set recreational catch quotas.