The terms overfishing and overfished are confusing because they address a similar subject. The difference between the two terms is subtle but significant. Overfishing refers to the current fishing rate which results in a higher harvest, or fishing mortality rate, than maximum sustainable yield (the maximum harvest level without negatively impacting the sustainability of the … [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…]
Bycatch is non-target catch within any fishery. Bycatch can be either different species from the target of the fishery or individuals from the target species, generally juveniles, which are not of a marketable size. Most bycatch is tossed back because it is illegal to possess or it has no commercial value. In certain fisheries, however, … [Read more…]
Promiscuous is a mating system where both sexes have multiple partners during the breeding system. In fishes, this is the most common mating system. Breeders make little or no mate choice and spawn with multiple partners, either sequentially or at the same time. Breeding aggregations of promiscuous spawners can make some fish species particularly vulnerable to fishing. The fish … [Read more…]