1.1 Origin
The European Inland Fisheries Advisory Commission (EIFAC) agreed, during its Sixth Session (Krakow, Poland, 18–22 May 1970), that a start should be made with the study of evaluation of fish stocks in large water bodies with the purpose of establishing practicable parameters for their assessment. Attention was at the same time drawn to the serious effects of sustained discharges of effluents on fish populations and also to the fact that the early detection of such effects is difficult, necessitating the development of methods whereby changes in fish populations can be assessed rapidly and inexpensively. It was pointed out that quantitative measurements of such changes are at present easily made only for small streams. It was, therefore, recommended (Recommendation 70/201 that EIFAC Sub-Commission I - Fisheries Biology and Management should be asked to consider the problem of developing methods whereby quantitative measurements of fish populations could also be obtained in lakes and large rivers. It was also suggested that estimates of the size of entire populations might not be necessary to evaluate the effects of pollution.
In partial fulfilment of these recommendations a working paper “Appraisal of Fishing Waters and their Fish Populations” (FI:EIFAC 72/SC 1–4) was presented at the Seventh Session2. The information contained in this document was, however, mainly qualitative in nature and insufficient to answer the questions as posed. The importance of making quantitative estimates of fish populations, both as indicators of pollution and as a basis for rational management policies was again emphasized. It was apparent during the sessional discussions that the main difficulties for quantitative estimates of fish populations in lakes and large rivers arose from problems of sampling and the interpretation of sampling results. It was decided, therefore, that the activities of EIFAC Sub-Commission I in this field be continued and expanded, and, in order to be able to formulate a long-term programme of research on these problems, it was recommended (Recommendation 72/22)3 “that a Symposium be held on the Methodology for the Survey, Monitoring and Appraisal of Fishery Resources in Lakes and Large Rivers, in conjunction with the Eighth Session of EIFAC”.
To aid in the preparation of this Symposium it was further recommended (Recommendation 72/23a) “that a working party be convened to establish a programme and prospectus with the minimum delay”.
Preparations for the Symposium were therefore organized by FAO/EIFAC. An organizational meeting was held in Rome in May 1972 with the following participation: Dr. T. Backiel (Poland), Prof. K. Tiews (Germany, Fed.Rep. of), Mr. P. Lamarque (France), Prof. H. Regier (Canada), Dr. J. Schärfe (Fish Production and Marketing Service, Fishery Industries Division, FAO), Mr. H.F. Henderson (Aquatic Resources Survey and Evaluation Service, Fishery Resources and Environment Division, FAO), and Mr. J.-L. Gaudet and Dr. R.L. Welcomme (EIFAC Secretariat).
It was decided that the Symposium should be focused on the methodology of sampling in deep waters, as opposed to those of small streams and ponds. Such waters were defined as those having a depth greater than 1.5 m over the major part of their area, and include lakes, rivers and canals that show little variation in depth or have seasonal deep water phases. It was also decided that the Symposium should cover subjects within the general scope of quantitative and qualitative aspects of such appraisal. Attention was drawn to the objectives of sampling fish, which should be performed in such a way that it enables interpretation of changes in characteristics of fish populations (e.g., population size, composition by age, length or sex, age at maturity, proportion of fish showing a specific feature or symptom, growth of individuals, distribution in space, etc.).
A detailed programme and prospectus for the Symposium were prepared and circulated in May 1972 for comments by selected experts. A definitive prospectus EIFAC: 74/Inf. 1 was issued mid-December 1972.
1 EIFAC Report, Sixth Session, Krakow, Poland, 18–22 May 1970, 71 p.
2 Amsterdam, Netherlands, 24–28 April 1972
3 EIFAC Report, Seventh Session, Amsterdam, Netherlands, 24–28 April 1972, 76 p.
1.2 Objectives
The objectives of the Symposium were to:
review the present methods used in sampling the fish populations of lakes and large rivers;
define the terms relative to methodology for the survey, monitoring and appraisal of fishery resources;
discuss the analysis of catches for the assessment of the properties of gear in sampling, and the interpretation of sampling data to establish characteristics of, and changes in, fish populations;
discuss new or improved methods to be used for such sampling;
formulate a long-term programme of research on such problems for the Member Nations of EIFAC as well as other countries concerned.
1.3 Organization
The Prospectus of the Symposium was distributed widely with invitations to scientists from EIFAC Member Nations and other European, American and African countries to prepare experience papers. The Symposium was held on 2–4 May 1974 in Aviemore, Scotland, at the Aviemore Conference Centre at the invitation of the Government of the United Kingdom, immediately preceding the Eighth Session of EIFAC, 6–10 May 1974.
Scientists and observers from twentyone countries participated (see Annex I). Simultaneous interpretation was provided in English, French and German, the latter by courtesy of the Government of the Federal Republic of Germany.
The documents (see Annex II) which formed the basis for the Symposium discussions were grouped as follows:
Panel review papers (8) - Summaries of existing knowledge and submitted experience papers prepared by the Panel Conveners.
Experience Papers (70) - Contributions by volunteering scientists, primarily on the use of specific types of gear including considerations of design, conditions of use, fish species or groups caught, selection characteristics, cost of operations, etc.
A Background Paper - “To Survey, Monitor or Appraise Fishery Resources: Some general concepts”.
At the opening meeting on 2 May 1974, Mr. A.V. Holden, of the United Kingdom, Chairman of EIFAC, welcomed the participants. Prof. K. Tiews of the Federal Republic of Germany, Chairman of Sub-Commission I - Fishery Biology and Management, reviewed the events and recommendations which led to the convening of the Symposium and outlined its general objectives. Symposium Chairman Mr. E.D. Le Cren (U.K.) then introduced the topic of the Symposium.
The Symposium was organized into consecutive meetings which were handled by panels of experts under the leadership of Panel Conveners. In Panel 1 the Convener and the various members briefly discussed various aspects of sampling theory as applied to the needs of various disciplines. In Panels 2 to 7 each Panel Convener summarized information available on his panel topic based on his own knowledge, a review of the literature and the papers submitted for the Symposium. The subject was then referred to each panel member in turn to bring out additional points or highlight aspects of the subject. Following each panel presentation, the other participants were invited to contribute information or ask questions of the panel. Following the panel meeting each Panel Convener prepared a summary report on the method under consideration. Section 5, Panel Reviews and Reports is based on these. Panel 8 considered the information presented to the Symposium and led a general discussion on methods for sampling. The conclusions reached during this panel formed the basis for the general conclusions of the Symposium (see Section 3).
At the close of the Symposium, the Chairman thanked the participants for their contributions, and, acting for the participants, expressed gratitude to the Host Government, and to the Secretariat for arranging the session.