Methods of Fisheries Science
1. Introduction


Fishing boats
Don's Introduction
Welcome to this expedition on the science of assessing the current status of fish stocks in the ocean and the interplay between the scientific assessment and effective management of these fish stocks, meaning the management of the commercial fishing industry and fishing pressure. We will first look at the management practice of a moratorium, a complete halt in fishing for an indefinite period of time, and how research surveying is used to monitor the recovery or lack thereof of the fish stock. Next we will examine the scientific analysis of the management practice of throwing the small ones back and how it leads to unintended consequences through evolution. We will then look at tracking fish though the entire ocean to learn about migrations and habitat as well as the use of sound to follow stocks. We will look at the recent practice of aquaculture, or fish farming, including new methods. We will end by looking at the ecosystems in which the fish live, and how monitoring and managing the entire ecosystem and habitat in ecosystem management.


This expedition should take about 75 minutes to complete. Listen to the news reports and move quickly through material.
This expedition has a total of about 50 minutes of audio and video segments. You should only need 1-2 minutes to answer each question in the worksheet.
It is one thing to identify the problem, but a completely different task to address it in an effective manner.
Objective: To learn about the ways that scientists attempt to assess the current status of marine fish stocks in order to address the decline in marine fisheries.

What is fisheries science?
The overall aim of fisheries science is to provide information to managers on the state and life history of the stocks. This information feeds into the decision making process. Fisheries science, economic, social and political considerations all have an impact on the final management decision.
What is a stock?
A "stock" is a population of a species living in a defined geographical area with similar biological parameters (e.g. growth, size at maturity, fecundity etc.) and a shared mortality rate.
What is the aim of stock assessment?
Stock assessment involves using mathematical and statistical models to examine the retrospective development of the stock and to make quantitative predictions to address the following fisheries management questions:

1) What is the current state of the stock?
2) What has happened to the stock in the past?
3) What will happen to the stock in the future under alternative management choices?
Excerpt from the Marine Insitute of Ireland -
Stock assessment can then lead to management of fish stock:
“We talk about managing fisheries, but we actually manage people’s behavior,” observes Dr. Jeff Cross, who is the Chief of Ecosystem Process Division of the Northeast Fisheries Science Center, National Marine Fisheries Service. “To do a good job of that we need to know a heck of a lot about what’s going on in the ocean.” Past legislation has seldom reflected the biology and life history of the species being managed. Most of what we know about fish stocks concerns species that have already been exploited, so there’s an urgent need for more habitat studies in particular and more information about marine ecosystems in general. So little is known about the habitat needs of most fish that in defining “essential fish habitat” managers are starting mostly from scratch. Cross, who provides essential fish habitat data to the New England Fishery Management Council says “Right now, we have to be very conservative because we just don’t have the information. We don’t know a lot about the functional relationship between fish and the habitat they occupy. My hope is that as we get the information, we won’t have to be quite so conservative in our designation of essential fish habitat.”
Excerpt from the American Museum of Natural History -
Created By:
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Don Reed
Dept. of Geology
San Jose State University
©Copyright 2008
Last Updated on 
August 31, 2009


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