Where does stock collide?

A stock is an amount that exists at a single moment, such as the wealth or capital held on a given date, as opposed to a flow, which is an amount that accrues over an interval of time, such as income earned during a year. Fisher's 1896 What is Capital? drew this distinction sharply, defining capital as a stock of wealth at an instant and income as the flow of services it yields over time. The referent is a level measured at a point in time, whose units carry no time dimension, and it is a different idea entirely from a share of company ownership, a breeding fish population, or a savory cooking base.[1]

Unit

An accumulated level at one instant, with no time dimension

Recovery means

Not applicable

Measured by

Read off as a balance or level at a date, and distinguished from flows by whether time appears in its units

In fisheries a stock is a distinct group of a species, self-sustaining through its own breeding, that is treated as one unit for assessment and management, and whose future depends on how many young it produces relative to its size. Ricker's 1954 Stock and Recruitment gave the classic account of how the number of new recruits depends on the size of the spawning stock, a relationship at the heart of judging sustainable catch. The referent is a living, reproducing population managed for yield, counted in fish or biomass, and it bears no relation to an ownership share, a level at an instant, or a culinary liquid.[2]

Unit

A breeding population of a species, in numbers or biomass

Recovery means

The stock rebuilds through recruitment as survivors spawn, so its abundance can recover after fishing eases

Measured by

Estimated by stock assessment from catch, survey, and age data, and modelled through stock-recruitment relationships