Fisheries technology and stock assessment

Semester 1

Semester 2

Semester 3

Semester 4



University of Algarve


This course consists of two parts: 1) Fisheries Technology, and 2) Stock Assessment. In the first part the student will learn about fishing gear, methods and technology and the impacts of fishing. In the second, the student will learn how to use different types of data, methods and models to evaluate the impact of fishing and the state of the resource.


Module 1. Fisheries technology. Introduction to the different types of fishing gear, classification of fishing gear, gear characteristics, methods of capture, and species and size selectivity. Static gear and active gear: gillnets and trammel nets, longlines, traps, pots, octopus pots, trawls, dredges and purse seine. Selectivity: species and size selectivity; selectivity models, parameter estimation, impacts of fishing gear: ghost fishing. The impacts of fishing: species and size selectivity, by-catch and discards, dynamics of mean size, degradation of habitats, population, community and ecosystem level effects of fishing. Mitigation of impacts: technological solutions (BRDs). Fish behavior in relation to fishing gear; “Fish Aggregating Devices” (FADs). Acoustic methods (fish detection).

Module 2. Stock assessment. Introduction to stock assessment and historical perspective .Roles and objectives of stock assessment and management. Management units. Sampling and data for stock assessment. Population dynamics: growth, mortality, and stock and recruitment. Parameter estimation. Stock assessment: surplus production models, yield per recruit models, virtual population analysis, cohort analysis, multi-species models. Indicators and reference points.


Fundamentals of population dynamics - basic knowledge of biology and ecology of marine organisms, in particular those that are harvested - some knowledge of fisheries and fishing gear types.


The objective of this course is to give an overview of fishing technology and fishing gears and methods. The impact of different fishing gears will be presented. The course will also provide the students with training in stock assessment and the provision of scientific advice for management of exploited living resources.


By the end of the course, students should have a good understanding of the different fishing gears, how they are used and their impact on living resources and the environment. They will also understand the concepts and methodologies that form/provide the basis of fisheries assessment , the philosophy behind the different types of models, their data requirements, and their limitations. The students should be capable of choosing the right model / methodology for stock assessment and management , and have the ability to interpret model outputs and formulate management advice.

Key skills acquired

Part 1: Fisheries Technology.

Know the main gear: characteristics, métiers, capture mechanisms, selectivity, impacts on species and in terms of by-catch and discards, impacts on the marine environment, and methods for mitigating the negative impacts of fishing. Knowledge about the most important aspects of the behavior of exploited species in relation to fishing gear. Knowledge of the basics of fish detection using sonar and other equipment.

Part 2: Stock Assessment.

Estimation of parameters, data analysis, application of diferente models (growth, recruitment, surplus production, yield per recruit),and methods for stock assessment (cohort analysis, VPA). Multi-specific models (surplus production, yield per recruit, cohort analysis). Capacity to use specialized software (for example FiSAT).


Bjordal, A. and S. Lokeborg. 1996. Longlining. Fishing News Books, University Press, Cambridge.
Caddy, J.F. and R. Mahon. 1995. Reference points for fisheries management. FAO Fish. Tech. Pap. No. 347. Rome, FAO 83 p.
Fernö, A. & S. Olsen (Eds), 1994. Marine fish behaviour in capture and abundance estimation. Fishing News Books Ltd
Garner, J. 1979. Pelagic and Semi Pelagic Trawling Gear. Iowa State Press.
Garner, J. 1989. Modern Deep Sea Trawling Gear. Iowa State Press.
Haddon, M. 2001. Modelling and quantitative methods in fisheries. Chapman & Hall/CRC
Gabriel, O., Lange, K., Dahm, E. and T. Wendt (eds.) 2005. Fish Catching Methods of the World. Blackwell Publishing, 536p.
Hilborn, R. and C. J. Walters. 1992. Quantitative fisheries stock assessment: choice, dynamics & uncertainty. Routledge, Chapman & Hall, Inc., New York, NY. 570pp.
Hoggarth, D.D.; Abeyasekera, S.; Arthur, R.I.; Beddington, J.R.; Burn, R.W.;Halls, A.S.; Kirkwood, G.P.; McAllister, M.; Medley, P.; Mees, C.C.; Parkes, G.B.;Pilling, G.M.; Wakeford, R.C.; Welcomme, R.L.2006.Stock assessment for fishery management – A framework guide to the stock assessmenttools of the Fisheries Management Science Programme (FMSP).FAO Fisheries Technical Paper. No. 487. Rome, FAO. 2006. 261p.
Hovgård, H. and H. Lassen. 2000. Manual on estimation of selectivity for gillnet and longline gears in abundance surveys. FAO Fisheries Technical Paper. No. 397. Rome, FAO. 2000. 84p.
Nédélec, C. and J. Prado. 1999. Definition and classification of fishing gear categories. FAO Fisheries Technical Paper No. 222 Rev. 1


2 exams (60%); written reports (40%)

Involved teachers

Karim Erzini

Contact hours