Abundance index (U) - A characteristic preferably proportional to the available biomass of the resource. The catch per unit effort, cpue (especially when the effort is expressed in appropriate units) is an important index..
Biological Limit Reference Point (LRP) - Biological reference point indicating limits of the fishery exploitation with regard to stock self-reproduction, aiming at conservation of the resource.
Biological Precautionary Reference Point (PaRP) - biomass levels (Bpa) and fishing levels (Fpa), established under the precautionary principle, concerning the reproduction of the stock, aiming at conservation of the resources. The assumptions and methods used to determine the PaRPs should be mentioned.
Biological Reference Point (BRP) - Values of F and B, taking into consideration the best possible catch and/or ensuring the conservation of the fishery resource. There are BRPs based on long term projections (LP), BRPs based on values observed during a certain period of years and BRPs based on the two previous criteria. The BRPs can be Target-Points (TRP), Limit-Points (LRP), and Precautionary Points (PaRP). In this manual the following biological reference points are referred to: Fmax, F0.1, Fhigh, Fmed, FMSY, Floss, Fcrash, Bmax, B0.1, Bmed, BMSY, Bloss, MBAL. Other biological reference points, used in management, like F30%SPR, are not mentioned in this manual.
Biological Target Reference Point (TRP) - Biological reference point indicating long term objectives (or targets), for the management of a fishery, taking into consideration the best possible catch and ensuring the conservation of the stock.
Biomass (B) - Weight of an individual or a group of individuals contemporaneous of a stock.
Capturability Coefficient (q) - Fraction of the biomass that is caught by unit of fishing effort.
Carrying capacity (k) - Capacity of the environment to maintain the stock living in it. It is, theoretically, the limit of the non exploited biomass (see intrinsic gross rate of the biomass, r).
Catch in number (C) - Number of individuals caught.
Catch in weight or Yield (Y) - Biomass of the stock taken by fishing. Yield does not necessarily correspond to landed weight. The difference between the two values, yield and landings, is mainly due to rejections to the sea of part of the catch which, for some reason (price, quality, space problems or even legal reasons), is not landed.
Cohort - Set of individuals of a fishery resource born from the same spawning.
Exploitation pattern of a gear (s) - Fraction of the individuals of a given size, available to the gear, which is caught. Also designated by Selectivity or partial recruitment.
Individual growth coefficient (K) - Instantaneous relative rate of change of a function of the individual weight, w, that is, H(w∞)-H(w), where w∞ is the asymptotic individual weight and H(w) is a function of w (frequently a power function, including the logarithmic function). The adopted models for the function H(w) have two constants, w∞ and K. Some models introduce one more parameter, b, which is used to obtain a general relation to include the most common individual growth relations. The constant K has the physical dimension of time -1.
Individual Quota (IQ) - Quota attributed to a vessel.
Individual Transferable Quotas (ITQ) - System of fisheries management characterized by the sale, at auctions, of the fishing annual vessel quotas.
Minimum Biomass Acceptable Level (MBAL) - Biological reference limit point that indicates a spawning biomass level under which the observed biomasses during a period of years, are small and the associated recruitments are smaller than the mean or median recruitment.
Number of individuals of a cohort or of a stock (N) - Number of survivals of a cohort (or a stock) at a certain instant or over an interval of time.
Partial recruitment - (see exploitation pattern)
Precautionary principle - This principle establishes that a lack of information does not justify the absence of management measures. On the contrary, management measures should be established in order to maintain the conservation of the resources. The assumptions and methods used for the determination of the scientific basis of the management should be presented.
Production models - Models that consider the biomass of the stock as a whole, that is, they do not take into consideration the age or size structure of the stock. These models are only applied in analyses that consider fishing level changes, as they do not allow the analysis of the effects of changes in the exploitation pattern, on catches and biomasses.
Quota (Q) - Each of the fractions in which the TAC was divided.
Absolute Instantaneous Rate of y, air(y) - Velocity of the variation of the function y(x), at the instant x.
Absolute Mean Rate of y, amr(y) - Mean velocity of the variation of the function y(x), during a certain interval of x.
Annual Survival Rate (S) - Mean rate of survivals of a cohort during one year, relative to the initial number.
Exploitation Rate (E) - Ratio between the number of individuals caught and the total number of individuals dead, over a certain period of time, that is, E = C/D.
Fishing mortality instantaneous rate (F) (Fishing mortality coefficient) - Relative instantaneous rate of the mortality of the number of individuals that die due to fishing.
Intrinsic rate of the biomass growth ® - Constant of the Production models that represents the instantaneous rate of the decreasing of the function H(K)-H(B), where B is the biomass, H(B) is a function of the total biomass, usually a power-function, (including the logarithmic function that can be considered a limit power function) and k is the carrying capacity of the environment. Some models introduce one more parameter, p, which is used to obtain a more general relation.
Natural mortality instantaneous rate (M) (Natural mortality Coefficient) - Instantaneous relative rate of the mortality of the number of individuals that die due to all causes other than fishing.
Relative instantaneous rate of y, rir(y) - Velocity of the variation of the function y(x), relative to the value of y, at the instant x.
Relative mean rate of y, rmr(y) - Mean velocity of the variation of the function y(x) relative to a value of y, during a certain interval of x.
Total mortality instantaneous rate (Z) (Total mortality coefficient) - Relative instantaneous rate of the mortality of the number of individuals that die due to all causes. Z, F and M are related by the following expression: Z=F+M.
Recruitment to the exploitable phase (R) - Number of individuals of a stock that enter the fishery area for the first time each year.
Selectivity - (see exploitation pattern)
Spawning or adult biomassa (SP) - Biomasss of the stock (or of a cohort) which has already spawned at least once.
Stock - Set of survivals of the cohorts of a fishery resource, at a certain instant or period of time. It may concern the biomass or the number of individuals.
Stock-Recruitment (S-R) relation - Relation between the parental stock (spawning biomass) and the resulting recruitment (usually the number of recruits to the exploitable phase). The models have two constants, α and k. The constant k has the physical dimension of weight and α has the dimension of weight-1. Some models introduce one more parameter, c, which is used to obtain a general relation that includes the most common relations.
Structural models - Models that consider the structure of the stock by ages or sizes. These models allow one to analyse the effects on catches and biomasses, due to changes in the fishing level and exploitation pattern.
Total Allowable Catch (TAC) - Management measure that limits the total annual catch of a fishery resource, aiming to indirectly limit the fishing mortality. The TAC can be divided into Quotas (Q) using different criteria, like countries, regions, fleets or vessels.
Total number of deaths (D) - Total number of individuals that die during a certain period of time..
Virgin biomass (VB) - Biomass of the stock not yet exploited.