Stock assessment
These include details on the age structure of the stock, age at first spawning, fecundity, ratio of males to females in the stock, natural mortality (M), fishing mortality (F), growth rate of the fish, spawning behavior, critical habitats, migratory habits, food preferences, and an estimate of either the total population or total biomass of the stock.
Stocks can be composed of multiple species due to their being harvested together or as a form of convenience for managers.
Landings are a record of the amount of fish sold and the numbers are typically reported in total weight.
Another common mode for acquiring fishery-dependent data is through portside sampling of the catch of both recreational and commercial fisherman to obtain age and length information on the stock.
A wide variety of methods and gear types are used to acquire fishery-independent data.
Overfishing describes the rate of removal from a stock and can be categorized as two different types: recruitment and economic.
Benchmarks that regulate fishing mortality include Fcurr, Fmsy, Emsy, and MFMT.
When MFMT is exceeded or the spawning stock size dips below MSST the fishery is shut down.
A benchmark that is currently gaining in popularity is SPR, spawning potential ratio.
[2] These reference points are meant to be more conservative than BMSY which is typically around 40-50% of unfished biomass, depending on the model and parameter values.
However recent work has suggested that more conservative reference points might be warranted for slow growing species depending on the model used.
A catch curve illustrates the proportions that different age and size classes are harvested by a fishery.
This model describes the stock solely in regards of biomass and the only used total catch and effort data.
In virtual population analysis models, catch-at-age data is used to estimate historical stock abundance.
Modern stock assessment methods use statistical approaches to "integrate" multiple sources of information to estimate management quantities and their associated uncertainty.
After a stock assessment is completed, the findings are provided to regional fishery management councils.
