A quota is the allowable number or amount of fish that can be harvested in a commercial or recreational fishery. This is a regulatory strategy to limit harvest. They are set each fishing season based on allowance for sustainable harvest (e.g., see Maximum Sustainable Yield). In certain commercial fisheries, quotas are essentially equivalent to a “share” … [Read more…]
A trap or pound net is a type of fishing gear with a complex organization of nets anchored to the substrate that “lead” or funnel fish into a final compartment (i.e., trap or pound) from which they cannot escape. In the Laurentian Great Lakes, this type of fishing gear is called a trap net and … [Read more…]
A gill net is a simple type of fishing gear that is staked to a substrate to create a wall of mesh. Gill nets are often made of a material, such as monofilament nylon, which is practically invisible to fish attempting to swim by. As the name implies, fish are often caught by the gills because … [Read more…]
Tubercles are skin nodules made of keratin, the same materials as hair, hooves, and fingernails. They are present on species representing at least 15 families of fishes, including even pet goldfish. In many species, tubercles are found only on males during the breeding season and are shed shortly there after. They are often called breeding … [Read more…]
BRD is an acronym for bycatch reduction device. Bycatch is non-target catch within any fishery. For certain fisheries, these modifications to the gear (i.e., BRDs) can help lower the amount of bycatch. For example, a turtle excluder device (TED) is a specific type of BRD designed to help turtles escape trawl nets. Especially in cases where fisheries have bycatch … [Read more…]
Fish population dynamics is the study of change in a fish population over time. Fundamentally, a population size after some time interval equates to the population size before that interval plus births (i.e., recruitment) and immigration and minus mortality and emigration. Many fish populations follow a logistic pattern of density-dependent growth. Beginning with a population … [Read more…]
An Exclusive Economic Zone (EEZ), as defined by the United Nations Convention on the Law of the Sea, is a 200 nautical mile jurisdiction granted to coastal nations for “sovereign rights for the purpose of exploring and exploiting, conserving and managing the natural resources, whether living or non-living, of the waters superjacent to the seabed and of … [Read more…]
Maximum sustainable yield (MSY) is a classic concept from fish population dynamics. It operates under the assumption that populations have a carrying capacity, or equilibrium size, where the the resources available match the population requirements and if individuals are removed from the population, they will be replaced (i.e., are renewable). When harvest removes a portion … [Read more…]
While gill rakers have no role in gas exchange, the predominant function of gills, they do perform an equally important function for filter-feeding fish – food acquisition. These bony projections serve as a sieve to trap food particles. They vary greatly in length and number and these characteristic differences have evolved with different feeding strategies … [Read more…]
Escapement is a term used in salmon management to mean, quite simply, how many salmon are able to “escape” premature death and complete their full life cycle. These escapees have run the gauntlet of natural mortality, recreational fishing, commercial fishing, and other life-threatening episodes for the opportunity to spawn in freshwater. Escapement is estimated by … [Read more…]