I do not know whether he was the first, nor whether others copied him or some later person, but Huntsman used the term "stock assessment" in a fisheries context in 1947. That term has been invoked many times through the following 77 years but I don't think that it has ever been defined. Perhaps I should say, never adequately defined. If I had to try now, I would say that a "stock assessment" is a science-based, quantitative evaluation of a specified fishery resource -- but not just any science-based evaluation. An assessment differs from scientific research in that its purpose is to yield the advice needed by management of the fishery for the resource in question. That advice might be some sort of allowable catch, a number of licences to be issued, a minimum size limit, a combination of those or something else entirely. However, it is always the purpose of the evaluation (that is: provision of management advice) that distinguishes a stock assessment from other analyses of a fish population.

It follows that example assessments will not be helpful unless they were prepared to meet the needs of a management situation similar to the one you face. Nor is it worthwhile for anyone to suggest an example until you can outline the management system that needs your scientific advice.

Next, there are a very great many approaches that have been used in stock assessments and probably many more that could be used. Some require huge quantities of data, vast prior knowledge of the resource and the ecosystem in which it is embedded, massive computing power and a lot of very advanced expertise. Others rely on very simple equations and a few guessed parameter values. Again: It is the specifics that matter and generalizations would be misleading.

I will offer a general warning regardless:

Most of the approaches that have been used in stock assessments in the last three-quarters of a century have been dangerous in unskilled hands. Most can be useful, when applied in appropriate circumstances by analysts who understand the limitations. Yet, whether superficially simple or massively complex, all assessment approaches are capable of generating wildly wrong answers, which mislead the unwary, confusing management decisions and ruining both fish and fisheries.

You will need deep understanding of the resource, the fishery, the management system and the available assessment approaches.

I know that that is not what anyone wants to be told but it is the reality.

Trevor Kenchington

Excellent answer from Trevor. I'll just add that stock assessments typically are based on mathematical modeling of the dynamics of the fish population(s) in question, i.e. growth, reproduction, mortality, etc. For examples of stock assessments, there are the North American Journal of Fisheries Management and Marine and Coastal Fisheries (links below) among many other sources.

https://afspubs.onlinelibrary.wiley.com/journal/15488675?journalRedirectCheck=true

https://afspubs.onlinelibrary.wiley.com/journal/19425120?journalRedirectCheck=true

A number of recent developments have made assessment methodologies more readily accessible and less data-hungry. Rainer Froese has been spearheading some particularly successful ones with a group of international scientists. See e.g. Article New developments in the analysis of catch time series as the...

Assessment in support of management should be particularly alert to listening to the experiences of practitioners, particularly small-scale fishers, out on the water every day, and be in line with a few rather simple principles. See Article Taking stock of global fisheries

Some initial elements can be derived even from length-weight relationships - support parameters and routines are regularly added in www.fishbase.org