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Threats to Marine Life: Unsustainable Fishing Practice. M.L. Anderson, 2009. Contents. The Problem Uses Destructive Practices Consequences of Overfishing Ways to Help Marine Laws, Parks & Zones Target Food Species Sea Sense – Sustainable Seafood Fish & Coral studies

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Threats to Marine Life: Unsustainable Fishing Practice

M.L. Anderson, 2009

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  • The Problem

  • Uses

  • Destructive Practices

  • Consequences of Overfishing

  • Ways to Help

  • Marine Laws, Parks & Zones

  • Target Food Species

  • Sea Sense – Sustainable Seafood

  • Fish & Coral studies

  • Abundance & Distribution

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What is Destructive Fishing?

  • Also known as exploitive fishing.

  • Refers to fishing practices that are unsustainable and damage the long-term health of fishery resources in order to profit from them.Occurs when people and/or companies are taking the easiest means possible to catch the most fish for a fast and easy profit. However, their careless actions are leading to pollution and damage the marine environment.

  • Because of the methods being used, many species of fish are in danger and their numbers are rapidly declining.

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Fisheries are threatened from human induced causes:

  • Overexploitation

  • Pollution

  • Habitat loss

  • Invasive species

  • Diseases

  • Habitat Degradation

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Fishing and Trade

  • Grouper and wrasse for live food fish trade.

  • Dead fish and invertebrates for food, medicinal products, ornamentals including sharks, sea cucumbers, sea stars, mollusks, sea horses.

  • Live fish, coral and other invertebrates for marine aquaria and hobby.

    = Selected removal of key species groups from coral reefs.

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Types of Destructive Fishing Practices

  • Bottom Trawling

  • Dynamite Fishing

  • Poison Fishing

  • Ghost Fishing

  • Over fishing

  • Anchoring

  • Muro-Ami

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Deep-water / Bottom Trawling

  • This fishing technique involves dragging giant bottom trawl nets along the sea floor. All marine life is caught in these nets and it also kills all habitats. Ultimately, everything in its path bets destroyed.

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Deep-water / Bottom Trawling

  • Its considered to be the most destructive fishing method used because it: removes species that live on the seafloor, reduces overall habitat complexity, can permanently change the types of species that live in areas of the seafloor, and homogenizes habitat, smoothing the sediment and breaking down complex structures.

  • They plunder seamounts, and are taking out many unknown worlds of the deep-sea before new species are even being found; it also decreases the available area for marine species to live and thrive in.

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Blast / Dynamite Fishing

  • Blast-fishing- Dynamite or other heavy explosives are detonated to startle fish out of hiding places. This practice kills other species and can crack and stress corals.

  • 40 countries affected by blast-fishing.

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Blast / Dynamite Fishing

Is a cheap method, using either dynamite or homemade bombs, which are easily made from available materials.The average 5 ounce beer bottle bomb leaves a crater of about 1- 2m in diameter, and kills 50-80% of coral in the area.

  • Shock waves from the explosion kill the fish, which either float on the water surface, or sink to the bottom. Then collected.

  • The underwater environment gets completely destroyed from the blast, leaving nothing but rubble behind.

  • Is illegal, but it is still practiced in up to 30 countries including SE Asia, Oceania, and is also very common in Eastern Africa.

  • The physical structure of coral reefs is at danger.

  • The re-growth of coral reef is a very slow process, and can take up to hundreds of years to regenerate.

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Poison / Cyanide Fishing

  • Cyanide fishing- Involves spraying or dumping cyanide onto reefs to stun and capture life fish, also kills coral polyps.

  • 15 countries have reported cyanide fishing.

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Poison / Cyanide Fishing

  • It is used to capture live fish for aquariums and food trades.

  • Fishers dive down to coral reefs and squirt cyanide or other poisons into the reef crevices. This stuns the fish, making them extremely easy to catch.

  • The most commonly used poisons are cyanide and bleach.

  • Impacts: range from coral bleaching to death.

  • Other species are also affected: It kills coral polyps (as well as killing their source food), symbiotic algae and other small reef organisms required for the upkeep of a healthy reef.

  • Ultimately, the entire reef ecosystem can collapse.

  • In addition, the stunned fish may hide or get caught in the coral crevices. As a result, the fisherman will physically rip the coral apart to get to the fish.

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What is Ghost Fishing?

Occurs when fishing gear or equipment is either abandoned or lost at sea.

  • The gear continues to catch marine life as it drops through the open water.

  • The gear is usually made of non-biodegradable material, making it very durable and will catching fish indefinitely.

  • The current scope of ghost fishing is unknown & almost impossible to study, but it is likely making a huge impact. In a survey conducted in the North Sea, it was estimated that 1/4 of the rubbish on the bottom of the sea floor is fishing nets.

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Ghost Fishing

  • There is a cycle of capture, decay, and attract.

  • When a net is first lost, catches decline as it gets weighed down & collapses.

  • As the fish stuck in this net decay, they attract scavenging organisms.

  • Once clear of this, the net will most like disentangle and return to the upright position, back to catching fish.

  • Storms can play a role in breaking the equipment up, resulting in less by catch.

  • In addition, birds, humans, and other organisms may be affected.

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What is Over Fishing?

  • When too much of one type of fish is being caught too fast.

  • The fish don’t have enough time to reproduce, therefore leading to a decline in numbers of that particular fish. If nothing is being done to protect them, ultimately they will become extinct.

  • If one type of fish becomes extinct, it can affect and ripple throughout the entire ecosystem. As a result, the overall ecology unit of our oceans are under stress and ultimately at risk of a collapse.

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Consequences of Overfishing

Grouper Spawning Aggregations

  • Fisheries collapse = impact on human communities

  • Local extinction of groupers (endangered in the U.S.)

  • Fisheries shift to less valuable species

  • Economic losses (decrease of exports)

  • Loss of ecotourism opportunities

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Anchors and Muro-ami

  • Muro-aminetting- Reefs are pounded with weighted bags to startle fish out of crevices.

  • Anchors- Dropped from fishing vessels onto reefs can break and destroy coral colonies.

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People can play a role too!

  • When fishing privately, fish only at designated areas and during the fishing seasons only.

  • Follow the regulations, such as catch limits

  • Keep your fishing location clean.

  • Practice ‘Catch & Release’

    • When releasing fish back into the water, remove the hook as safely as possible & return it back into the water as soon as possible.

  • Know what you’re eating; if it’s an endangered species, pass it up for something else.

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What Can You Do? Know your Marine Park Regulations and Marine Conservation Laws

  • Example: Cayman Islands Marine Seasons:

  • Lobster Season – Open season Dec 1st –Feb 28th; 3 pp, 6 per boat.

  • Groupers – 12” min. Dec 1st – Feb 28th open season. Grouper holes protected

  • Conch- Closed season May 1st – Oct 31st

  • Whelks - Closed season May 1st – Oct 31st

Photo: Diana Schmitt

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Marine Zones

Marine Park Zone

  • No taking fish, no anchoring, except with a license.

    Environmental zone

    No taking of any marine life.

    Replenishment Zone – No taking of conch or lobster by any means.

    Line fishing and anchoring permitted with a license.

    Anchor and chain must not touch coral.

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Marine Parks

Marine Parks are an important way to balance tourism and fisheries.

The design of marine parks has evolved from a philosophy of total protection of small areas to one allowing multiple uses of large areas with an integrated management system that takes account of all resources management goals, including total protection.

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Caribbean Targeted Food Species

Spiny lobster

Panulirus argus

Nassau grouper

Epinephelus striatus

Queen conch

Stombus gigas

Yellowtail snapper

Ocyurus chrysururs

West Indian whelk

Cittarium pica

Queen triggerfish

Balistes vetula

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Cayman Sea Sense

….is a sustainable seafood education program dedicated to helping restaurants and their customers make informed and environmentally positive seafood choices. The project will assist local chefs and restaurant owners reduce the number of non-sustainable seafood items on their menus.

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Cayman Sea Sense

The primary goals are:• to educate the general public about fisheries and aquaculture issues facing our oceans • to raise awareness about the impact that the choices we make have on sustainable fisheries management practices when we purchase seafood products • to lessen the impact of the Cayman Islands restaurant industry on the worlds fragile ocean resources.

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Sustainable Seafood

Defined as:• A species that is abundant and resilient to fishing pressures.• A species that is well managed with a comprehensive management plan based on current research.• A species that is harvested in a method that ensures limited bycatch on non-target and endangered species.• A species that has a method of catch which ensures there is limited habitat loss associated with the harvesting method.

Adopted from Vancouver Aquarium’s Ocean Wise program

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Cayman Sea Sense


  • National Trust for the Cayman Islands

  • Boatswain’s Beach

  • Department of Environment

  • Cayman Islands Tourism Association

  • Department of Tourism

  • Partnering Restaurants and Chefs

  • Progressive Distributors

  • The Sea Sense Logo:

  • Allows consumers to choose sustainable seafood options.

  • Allows partnering restaurants to be promoted as making a positive choice for the oceans.

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Sustainable Seafood

Defined as:• A species that is abundant and resilient to fishing pressures.• A species that is well managed with a comprehensive management plan based on current research.• A species that is harvested in a method that ensures limited bycatch on non-target and endangered species.• A species that has a method of catch which ensures there is limited habitat loss associated with the harvesting method.

Adopted from Vancouver Aquarium’s Ocean Wise program

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Sustainable Fishing

I love sustainable fishing practices!

“Providing for the needs of the present without jeopardizing the needs of the future.”

Sustainable development is a worthy goal of coral reef management because it accepts reality that humans have need for coral reef resources.

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Effects on Society

  • destroys habitats

  • inhibits the growth of new coral

  • reduces fish stock

  • disrupts the food web & ecosystem balance

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Fisheries data addresses:

Diversity of fish populations

Interactions between fish populations and reef health

Economic importance of select species

Population changes over time

Based on AGRRA protocol:

Fish identified by species and size estimate

10 30m belt transects per site

30 min. roving diver survey

CCMI Research: Fisheries Abundance and Distribution

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Fishery Abundance and Distribution of Key Species

Blue tang

Acanthurus coeruleus

Nassau grouper

Epinephelus striatus

Four-eyed butterflyfish

Chaetodon capistratus

Queen triggerfish

Balistes vetula

Queen parrotfish

Scarus vetula

Yellowtail snapper

Ocyurus chrysururs

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CCMI Fisheries and Coral Study Sites: LCI, BWI


Grape Tree Bay

Mixing Bowl

Coral City

Grundy’s Garden

Preston Bay

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CaribbeanMarine Life

It is important to maintain the amazing diversity of fish, turtles, invertebratesand rays in our coastal areas and to protect our coral reefs.

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Factors for fish and coral reef habitats…

  • Proximity to the coast.

  • Exposure to wave action.

  • Currents.

  • Light levels.

  • Amount of algae.

  • Plankton and other food.

  • Abundance/shape/varieties of coral and other shelter.


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Spawning (sperm and eggs released in open water).

Scattering eggs over substratum.

Preparing/defending nests on bottom.

Carrying fertilized eggs inside mouth or pouch.

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Life Cycle

3. After settlement, the fish establish relatively small home-ranges with the majority spending the rest of their lives on the same reef. This is the benthic stage.

  • Two stages, pelagic and benthic. Pelagic (oceanic) larval stage is when the fish float freely in the water.

  • In around 9 to 100 days, the fish find a place to live and settle. The pelagic stage determines geographical size of population units. This is the only period when fish disperse for long distances.

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Feed on algae located on the coral reefs.

Control algae abundance on the reef and keep the hard surfaces clean and allow new corals to grow or invertebrates to attach to the substrate.

There is some evidence that herbivorous fish have bacteria in their guts, much like cows, to allow them to digest more nutrients from the algae.

Surgeonfish, damselfish, parrotfish.

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Invertebrate Predators

They play an important role on composition of prey communities.

Butterfly fish, angelfish, wrasse.

This group includes the largest number of coral reef fish species.

They eat coral polyps, sessile inverts, and some mobile inverts.

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Omnivores / Carnivores

They influence the composition of prey communities.

Eat well-armored inverts, crustaceans, star-fish, some algae.

Filefish, triggerfish, puffers.

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Fragile Balance…

The disturbance of any of these feeding groups may directly affect another group or the entire reef community.

There is such a fragile balance holding the coral reef fish community together like links in a chain.