Fishionary

A blog about fish words!

By Abigail Lynch

A blog about fish words!

MSY

TAC

Posted by abby on September 28, 2018

TAC is an abbreviation for Total Allowable Catch (image credit: mimiculture.com; icon design: Scott de Jonge from Flatiron).

TAC is Total Allowable Catch.  This is the upper limit in the amount of fish, either by weight or number, that a fishery is allocated in a given season or year.  TACs can apply to the targeted fish and/or bycatch, where once the limit is reached the fishery is closed for the remainder of the applicable time frame.  Often, the TAC is set based on an assessment of the stock status for the fishery, such as maximum sustainable yield (MSY).

In open-access or “derby” style fisheries, there is a free-for-all competition until the TAC is exhausted.  This can lead to risky or unsafe behavior, where vessels may continue to operate in hazardous conditions in order to harvest a larger proportion of the TAC.  In order to avoid accidents from such situations, some fisheries have opted for quota-based management systems where the TAC can be divided into catch shares, such as Individual Transferable Quotas (ITQs).

Posted in: T | Tagged: bycatch, fishing regulation, ITQ, MSY, quota, sustainable harvest, TAC

Population dynamics

Posted by abby on March 30, 2018

Fish population dynamics (image credit: Katherine Nicholson, slideplayer.com)

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 size where space and food are not limiting, the population grows rapidly in an exponential pattern; at a certain population density, population growth slows and stabilizes at a given carrying capacity.

Density-dependent factors governing fish population dynamics include competition, predation, disease, and parasitism.  Fish population dynamics can also be driven by density-independent abiotic factors such as temperature, dissolved oxygen, and water chemistry.

In fisheries, these basic population dynamics principles can be applied to harvest strategies to estimate maximum sustainable yield (MSY) with the goal to prevent overfishing.

Posted in: P | Tagged: maximum sustainable yield, MSY, overfishing

Maxium sustainable yield (MSY)

Posted by abby on January 26, 2018

Optimizing fishing effort (Diagram credit: http://ib.bioninja.com.au).

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 of the population, it  lowers pressures on the population’s associated resources, such as food and habitat, allowing the remainder of the population to benefit from less competition and balance the population back to the carrying capacity.  By this theory, the surplus biomass can be harvested sustainably, without long-term impacts to the population.

MSY is a commonly applied fisheries management tool, and even a guiding principle of the Magnuson-Stevens Fishery Conservation and Management Act, the primary legislation governing marine fisheries management in United States federal waters.  However, it is important to note that there are many situations in which the assumptions of MSY are not met which result in overfishing and unsustainable practices.

Posted in: M | Tagged: carrying capacity, Magnuson-Stevens Act, MSY, overfished, overfishing, population dynamics, renewable resources, sustainable harvest

Fishionary Alphabet

  • Home
  • A
  • B
  • C
  • D
  • E
  • F
  • G
  • H
  • I
  • J
  • K
  • L
  • M
  • N
  • O
  • P
  • Q
  • R
  • S
  • T
  • U
  • V
  • W
  • X
  • Y
  • Z

Recent Posts

  • Kype
  • Fish conservation zones (FCZs)
  • Amphidromous
  • Cartilaginous
  • Cetí (Español – English)
The views expressed in these posts are solely the views of the AFS member who wrote them and do not necessarily reflect the views of the American Fisheries Society (AFS), its officers, or the U.S. Geological Survey. Both organizations make no representation on the accuracy of opinions expressed in this blog. AFS merely hosts voluntary blogs as a place for members to share their personal views with other AFS members and to engage in friendly exchanges on fish topics.

Copyright © 2022 Fishionary.

Theme by themehall.com.