Modifying Fishing Gears to Achieve Ecosystem Objectives

John Willy Valdemarsen, FAO

&

Petri Suuronen, Finland

How fishing gears affect the ecosystem

How fishing gears affect the ecosystem

• Removal of organisms that, for various reasons should not been taken (e.g. juveniles, threaten species)

• Alteration of the habitat that may be negative to the organisms living there

> Injure benthic organisms

> Reduce habitat complexities

> Reduce biodiversity

• Removal of organisms that, for various reasons should not been taken (e.g. juveniles, threaten species)

• Alteration of the habitat that may be negative to the organisms living there

> Injure benthic organisms

> Reduce habitat complexities

> Reduce biodiversity

SSpawningpawning stock sizestock size

Too few Too few spawners!spawners!

Catch consisting mainly of Catch consisting mainly of small fishsmall fish and … and …

large part of them are large part of them are discardeddiscarded!!(estimated discard rate 12-20% in numbers)(estimated discard rate 12-20% in numbers)

Harvesting pattern of Baltic Cod today:Harvesting pattern of Baltic Cod today:

Mortality other thanMortality other thanfishery (M) fishery (M)

Examples of gear modifications that reduce unwanted by-catch

• Turtle Excluder Device (TED)

• Shrimp-fish separators

• Size selective grids

• Square mesh windows

• Medina panel/ “Backdown” principle to avoid dolphins in tuna purse seining

• Bird scaring lines in longline fishing

• Selective trap nets

• Turtle Excluder Device (TED)

• Shrimp-fish separators

• Size selective grids

• Square mesh windows

• Medina panel/ “Backdown” principle to avoid dolphins in tuna purse seining

• Bird scaring lines in longline fishing

• Selective trap nets

Turtle Excluder Device for Shrimp trawlsTurtle Excluder Device for Shrimp trawls

• Releases Turtles

• Retains target shrimps

• Debris blocking the grid can cause some loss of catch

• TEDs are mandatory in many tropical shrimp fisheries

• Further developments are directed to also avoid fish bycatch

• Releases Turtles

• Retains target shrimps

• Debris blocking the grid can cause some loss of catch

• TEDs are mandatory in many tropical shrimp fisheries

• Further developments are directed to also avoid fish bycatch

Nordmøre grid for separating shrimp and fish Nordmøre grid for separating shrimp and fish

• Retains shrimp

• Releases fish by-catch

• Improves quality of target catch

• Reduces sorting work onboard

• Increases yields of non-targets for other fisheries

• Mandatory in a number of fisheries

• Retains shrimp

• Releases fish by-catch

• Improves quality of target catch

• Reduces sorting work onboard

• Increases yields of non-targets for other fisheries

• Mandatory in a number of fisheries

Size sorting gridSize sorting grid• Small, juvenile fish are

released

• Size sorting with grids is less dependant on high catch rates than meshes

• Properly designed and used size sorting grids may allow fishing to continue in areas where the abundance of young fish is high

• Small, juvenile fish are released

• Size sorting with grids is less dependant on high catch rates than meshes

• Properly designed and used size sorting grids may allow fishing to continue in areas where the abundance of young fish is high

Square mesh window to release small fishSquare mesh window to release small fish

• Square meshes stay open during towing

• Square mesh panels are cheap and simple size selective devices

• Square mesh windows are mandatory in some fisheries

• Square meshes stay open during towing

• Square mesh panels are cheap and simple size selective devices

• Square mesh windows are mandatory in some fisheries

By-catch while purse seiningBy-catch while purse seining

• Incidental catch of dolphins while purse seining for tuna species (350 000 taken in the Pacific fisheries in the 60ies)

• Capture of juvenile tuna and other non-target fish while fishing with Fish Aggregating Devices (FADs)

• Incidental catch of dolphins while purse seining for tuna species (350 000 taken in the Pacific fisheries in the 60ies)

• Capture of juvenile tuna and other non-target fish while fishing with Fish Aggregating Devices (FADs)

Medina Panel and backdown principle to release dolphinsMedina Panel and backdown principle to release dolphins

Modified salmon trap to avoid seal captureModified salmon trap to avoid seal capture

• Grid in the entrance prevents seals from entering the trap

• Strong outside netting also prevents seals from breaking into the trap

• The captured salmon is safe from seal attack and seals are not trapped

• Grid in the entrance prevents seals from entering the trap

• Strong outside netting also prevents seals from breaking into the trap

• The captured salmon is safe from seal attack and seals are not trapped

Bird-Scaring line to reduce seabird capture during longline fishing

Bird-Scaring line to reduce seabird capture during longline fishing

• Seabirds try to take bait from hooks during setting of longlines and might self be hooked

• This is particularly a problem for albatrosses and petrels in Southern Oceans

• Mitigations tools such as scaring lines significantly reduce the problem

• Seabirds try to take bait from hooks during setting of longlines and might self be hooked

• This is particularly a problem for albatrosses and petrels in Southern Oceans

• Mitigations tools such as scaring lines significantly reduce the problem

How fishing gears impact the ecosystem

How fishing gears impact the ecosystem

• Alteration of the habitat that may be negative to the organisms living there

> Injure benthic organisms

> Reduce habitat complexities

> Reduce biodiversity

• Alteration of the habitat that may be negative to the organisms living there

> Injure benthic organisms

> Reduce habitat complexities

> Reduce biodiversity

Three examples of bottom habitats

Three examples of bottom habitats

Muddy bottom Sandy/stony bottom Coral bottom

Overall effect of various fishing gears on bottom habitats

Overall effect of various fishing gears on bottom habitats• Bottom otter trawls (---)

• Beam trawls (----)

• Dredges (-----)

• Demersal seines (--)

• Bottom-set gillnets (-)

• Demersal longlines (-)

• Traps and pots (-)

• Bottom otter trawls (---)

• Beam trawls (----)

• Dredges (-----)

• Demersal seines (--)

• Bottom-set gillnets (-)

• Demersal longlines (-)

• Traps and pots (-)

Possible technical gear modifications

Possible technical gear modifications

• Lifting gear parts off the bottom

• Use electrical stimuli to scare target objects off the bottom

• Lifting gear parts off the bottom

• Use electrical stimuli to scare target objects off the bottom

Trawldoor track on sandy/stony bottom

“Smart trawling technology” “Smart trawling technology”

• Reduced bottom impact of trawl gears can be achieved by;

– Lifting the trawl doors from bottom

– Using dropper chain instead of roller gear to keep bottom contact

– Other ground gear designs (size, material, and construction of rollers)

• Reduced bottom impact of trawl gears can be achieved by;

– Lifting the trawl doors from bottom

– Using dropper chain instead of roller gear to keep bottom contact

– Other ground gear designs (size, material, and construction of rollers)

Change of fishing practiseChange of fishing practise

• Close the most sensitive areas for fishing (Monitor activity with VMS)

• Concentrating fishing effort where density of fishing objects are highest (High CPUE)

• Replace harmful fishing gears with gears that are less harmful to the bottom habitat, like a fish pot!!!

• Close the most sensitive areas for fishing (Monitor activity with VMS)

• Concentrating fishing effort where density of fishing objects are highest (High CPUE)

• Replace harmful fishing gears with gears that are less harmful to the bottom habitat, like a fish pot!!!

Fish pot

Conclusions (1)Conclusions (1)

• Modifications of fishing gears has significantly helped to reduce by-catches

• Techniques that are not practical or increase costs will most likely fail

• Economic rewards should be offered for the creation and use of gear modifications that reduce by-catches and minimize impacts on habitats

• Co-operation between fishing industry, scientists and other stake holders is fundamental

• Modifications of fishing gears has significantly helped to reduce by-catches

• Techniques that are not practical or increase costs will most likely fail

• Economic rewards should be offered for the creation and use of gear modifications that reduce by-catches and minimize impacts on habitats

• Co-operation between fishing industry, scientists and other stake holders is fundamental

Conclusions (2)Conclusions (2)• Characteristics of various trawls grounds should be better

known to focus the development and implementation of proper technologies and practises

• Reduction of impact on grounds that has a “rich” biodiversity should be given highest priority

• Areas with a complex biodiversity, like corals, should be closed for sensitive fishing like trawling and dredging

• Fishing practice that has reduced bottom interaction should be promoted on grounds with an intermediate type of biodiversity

• Characteristics of various trawls grounds should be better known to focus the development and implementation of proper technologies and practises

• Reduction of impact on grounds that has a “rich” biodiversity should be given highest priority

• Areas with a complex biodiversity, like corals, should be closed for sensitive fishing like trawling and dredging

• Fishing practice that has reduced bottom interaction should be promoted on grounds with an intermediate type of biodiversity

THANK YOUTHANK YOU