APES 3.8 - Fisheries

Lesson 3.8

Aquaculture

Fisheries

Commercial Fishing

LONGLINE

GILL NETTING

TRAWLING

PURSE SEINE

Bycatch vs. Target Species

Ways to Fish Sustainably

Ways to Make Commercial Fishing More Sustainable

the maximum amount of fish that can be caught from a stock while still allowing the population to replenish itself over time

• Limit the age or size of fish caught
• Modify fishing techniques to reduce bycatch
• Enact laws & treaties that protect critical species
• Set catch limits based on Maximum Sustainable Yield

Trawling

Trawling involves dragging a large, weighted net along the ocean floor (bottom trawling) or in the water column (midwater trawling) to catch fish and other marine life. Bottom trawling is typically used to target bottom-dwelling species like shrimp and cod.

ENVIRONMENTAL CONSEQUENCES

• Habitat Destruction: Bottom trawling causes significant damage to the seafloor, destroying habitats like coral reefs, sponge fields, and seagrass beds, which are essential for marine biodiversity.
• Bycatch: Trawling is indiscriminate and catches many non-target species, leading to waste and increased mortality among marine life.
• Sediment Disturbance: Bottom trawling stirs up sediment, releasing nutrients and pollutants, which can alter water quality and harm ecosystems far beyond the trawling location.

Commercial Fishing

Commercial Fishing refers to large scale fishing operations that are for profit. Commercial fishing contributes to overfishing through the tragedy of the commons, a situation where individuals, acting in their own self-interest, overuse a shared resource, ultimately depleting it. In fisheries, the ocean’s fish populations are a common resource accessible to all, and there’s little incentive for individual fishers to limit their catch. As each fisher aims to maximize their own profit, they collectively harvest fish at a rate faster than populations can naturally replenish. This excessive fishing pressure leads to declining fish stocks, ecosystem imbalances, and, if left unchecked, the collapse of entire fisheries, harming both the environment and future livelihoods.

Gill Netting

Gill netting uses a wall of netting that fish swim into and become entangled by their gills. Nets can be set at different depths and vary in mesh size depending on the targeted species.

ENVIRONMENTAL CONSEQUENCES

• Bycatch: Gill nets often entrap non-target species, including marine mammals, sea turtles, and seabirds, which can suffer injuries or die if entangled.
• Ghost Fishing: If nets are lost, they continue trapping animals, leading to ongoing harm to marine life and ecosystem imbalance.
• Habitat Destruction: Nets can damage sensitive habitats like coral reefs and seagrass beds when deployed in shallow waters.

Longline Fishing

Longline fishing uses a main fishing line with baited hooks attached at intervals, which can extend for miles. The line can be set near the surface or deeper in the water, targeting species like tuna and swordfish.

ENVIRONMENTAL CONSEQUENCES

• Bycatch: Longline fishing often catches unintended species, including seabirds, sea turtles, and sharks, which can lead to population declines in these vulnerable species.
• Overfishing: The efficiency of longlines can contribute to overfishing if regulations aren’t strictly enforced, putting pressure on targeted fish populations.
• Entanglement: Lost or abandoned longlines can continue to catch and kill marine life in a phenomenon known as "ghost fishing."

Purse Seine Fishing

Purse seine fishing involves encircling a school of fish with a large net that is then drawn tight at the bottom, like a drawstring purse. This method is commonly used for schooling fish, such as tuna and mackerel.

ENVIRONMENTAL CONSEQUENCES

• Bycatch: Although it can be somewhat selective, purse seine fishing still catches non-target species, particularly when schools of target fish are mixed with species like dolphins or sharks.
• Overfishing: The high efficiency of purse seines allows for the capture of large amounts of fish at once, which can contribute to overfishing and disrupt local ecosystems.
• Marine Mammal Harm: When dolphins and other mammals associate with schools of fish, they can be captured and harmed, even if efforts are made to release them.

Aquaculture = Fish Farming

Aquaculture is the practice of raising aquatic organisms, such as fish, shellfish, and algae, in controlled environments. It can take place in a variety of water environments, including ponds, rivers, lakes, the ocean, and man-made systems on land.