Fishing methods

underwater diver survey

• Method: Divers use transects or point counts to visually identify and count species.
  Key Idea: Provides non-invasive, high-quality data on fish behavior and habitat health.

Anesthetics

• Purpose: Chemical agents (like clove oil or MS-222) used to calm or sedate fish.

• Key Idea: Essential for safe handling, measuring, or tagging to reduce fish stress and injury.

Piscicides

• Method: Chemicals (like Rotenone) added to water to kill specific fish populations.

• Key Idea: Often used for invasive species eradication or total population sampling in closed systems.

Hook and Line: long line

• Setup: A main line with thousands of baited "snood" lines branching off.

• Key Idea: Can stretch for miles; used for pelagic fish (tuna, swordfish) or demersal fish (halibut).

Hook and line: drop line

• Setup: A single vertical line with multiple baited hooks, weighted at the bottom.

• Key Idea: Used primarily for deep-sea reef fish or "bottom-fishing" in specific spots.

Beach Seines

• Method: A net deployed from shore, looped out, and pulled back to the beach by hand or vehicle.

• Key Idea: Targets schooling fish in shallow, near-shore waters.

Haul seines

• Method: Similar to beach seines but often deployed further out and hauled into a boat or platform.

• Key Idea: Relies on "encircling" the fish and dragging them to a collection point.

Gill nets

• Mechanism: Invisible vertical mesh walls that snag fish by their gill covers (opercula).

• Key Idea: Highly size-selective based on mesh "stretch" size.

Trammel nets

• Setup: Three layers of netting (two outer large-mesh, one inner fine-mesh).

• Key Idea: Fish push the fine mesh through the large mesh, creating a "pocket" that traps them.

Otter trawls

• Mechanism: A large cone-shaped net kept open by "otter boards" (doors) that act as underwater kites.

• Key Idea: Dragged along the seafloor (demersal) to catch shrimp or groundfish.

Round haul nets

• Mechanism: A massive wall of net circles a school; the bottom is "pursed" shut like a drawstring bag.

• Key Idea: Targets massive schools of pelagic fish (sardines, tuna).

Maze gear/pot gear

• Mechanism: Enclosed cages with a one-way "funnel" entrance.

• Key Idea: Passive gear using bait to lure targets; primarily used for crustaceans (crabs/lobsters).

Fyke nets

• Setup: A series of hoop nets with internal funnels, often used with "wings" to guide fish in.

• Key Idea: Used in shallow or moving water for eels and migratory fish.

Electrofishing

• Mechanism: Emits an electric field into the water to induce "galvanotaxis" (forced swimming toward the anode).

• Key Idea: Stuns fish momentarily for easy capture, measurement, and release.

Hand fishing

• Method: Placing a hand inside underwater holes to provoke a fish (usually catfish) into biting.

• Key Idea: Highly selective but physically dangerous to the fisher.

Dredges

• Mechanism: Heavy metal frames with chain bags dragged across the ocean floor.

• Key Idea: Used to scrape up bottom-dwellers like scallops and clams.

Isaac Kidd Nets

• Design: A specialized midwater trawl with a V-shaped diving vane to keep it stable at high speeds.

• Key Idea: Used by researchers to catch deep-sea "macro-plankton" and small mesopelagic fish.

Cast Nets

• Method: A circular net with weights around the edge, thrown by hand to spread flat.

• Key Idea: Relies on the skill of the thrower to "pancake" the net over schooling baitfish.