Fisheries Technology
Fisheries Technology tests your ability to connect fish biology with the gear, sampling tools, and identification methods used in the field. Questions typically cover taxonomy, meristic and morphometric characters, ageing structures, gear classification, and the hydrographic measurements that explain fish distribution.
Identification: countable versus measurable
- Meristic characters are countable: fin rays and spines, lateral-line scales, gill rakers, vertebrae, branchiostegal rays.
- Morphometric characters are measurable: fork length, head length, body depth, eye diameter; they are usually expressed as ratios or percentages of standard length.
- Write fin formulas conventionally, separating spiny and soft rays (for example, D. XI, 12), and state whether counts include rudiments.
- Ageing uses otoliths, scales, or vertebrae; annual ring deposition must be validated for the species and locality before ages are assigned.
Gear classification and selectivity
FAO's standard groups include surrounding nets, seine nets, trawls, dredges, lift nets, falling gear, gillnets and entangling nets, traps, hooks and lines, scoop nets, pumps, and harpoons. Gillnets are passive entangling gears whose catch is governed by mesh size; trawls are active towed gears whose selection depends mainly on codend mesh and mesh shape.
Worked example
A fish has a fork length of 40 cm and a maximum girth of 20 cm. What stretched mesh would best retain it in a gillnet? A fish is gilled when its girth equals the mesh perimeter. For a diamond mesh, perimeter = 4 × bar length and stretched mesh = 2 × bar length, so mesh = girth ÷ 2 = 10 cm, or about 25% of fork length. This illustrates the common mesh ≈ 0.25 FL rule of thumb.
Traps that cost marks
Mixing meristic and morphometric counts; capitalizing the species epithet; treating every otolith ring as annual; confusing bar length with stretched mesh; and misclassifying gillnets as traps.