ASSESSMENT AND MONITORING OF THE FISHERY RESOURCES AND THE ECOSYSTEMS IN THE STRAITS OF SICILY

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Workshop on the Standardization of trawl surveys protocol in the MedSudMed project area
(05-09 May 2003, Mazara del Vallo - Italy)

Background
Organization
Participation
Agenda
 
Background

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The seminar is a follow-up of the Expert Consultation on Spatial distribution of demersal resources in the Straits of Sicily and the influence of environmental factors and fishery characteristics, held in Malta from 10 to 12 December 2002. The agreed work-plan includes processing of trawl surveys data; however, in order to allow data comparison between participating countries, it was been decided to adopt the same sampling and processing protocol. The scope of this seminar was to present existing sampling designs and data processing procedures adopted in on-going monitoring trawl surveys, compare them and agree on common methodologies based on existing ones.

Some of the research institutions of the MedSudMed participating countries already participate in international and/or national programs and conduct annual trawl surveys. Important georeferenced databases have been produced on abundance indices of several species, and biological information. In line with the priorities of the GFCM-SAC of providing information on demersal resources, MedSudMed Project's activities concentrate on improving the knowledge on the spatial distribution and description of fisheries resources.

Organization

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The organization is detailed in the provisional agenda. Each participating country (Tunisia, Malta, Libya, Italy) presented the status and aim of its fisheries research activities, addressing each one of the points detailed below. The protocol used for the different steps of bottom trawl surveys were presented in plenary session; thereafter, three working groups met in separate sessions to examine, add and agree on specific and detailed methodologies for each one of the issues. The working groups then presented their documents to further discussion and approval of a common protocol in plenary session.
Planning of activities at sea and fishing gears
Processing of the catches - biological sampling
Biological information on target species
Identification and discussion of further data sampling and measurements
Data management and processing
 
Planning of activities at sea and fishing gears

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This topic concentrated on the operations at sea and fishing procedures. The protocol adopted by national programs for the allocation of the hauls was presented. This regards the sampling area, the equipment, the sampling design, and the fishing operations themselves. The following issues were addressed:

a.    study areas;

b.    sampling periods and frequency;

c.    sampling design presently used by the participating Institutes: stratification criteria and spatial allocation to   strata;

d.    haul characteristics (number, coding, day timing, boat speed duration, direction, validity criteria, ...);

e.    available boats and navigational devices;

f.     plan and characteristics of the gear (setting and using the scanmar if any,rigging, mesh, net design, etc.).

Processing of the catches - biological sampling

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This topic dealt with the processing methods of the catches. General information was given on the target and by-catch species, and on the methodology used to process, measure and preserve the samples. The following issues summarize the type of information that was presented and discussed:

a.      sub‑sampling;

b.      target species;

c.      other representative species;

d.      by‑catch species;

e.      grouping level of the above species;

f.       methodology of basic measurements (total length, carapace/mantle length, etc.);

g.      material preservation at sea and/or in laboratory;

h.      otolith (or other hard parts such as vertebrae or scales) collection and preservation.

Biological information on target species

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More specific biological sampling procedures done on the target species were also discussed. This topic included more detailed processing, such as organ identification and measurement, biological sampling and analysis. The issues listed below include mainly activities related to determination of sexual maturity:

a.     sex determination;

b.     macroscopic maturity;

c.    other morphometric measurements (e.g. girth, pterigopod length, etc.);

d.     organ weights (gonads, liver, nidamental glands, etc.).

Identification and discussion of further data sampling and measurements

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 These include:

a.       measurement of bottom water temperature;

b.       eggs and larvae collection using bongo nets;

c.       dredging or grabbing for associated biocenosis;

d.       analysis of discards;

e.       tagging and mark-recapture studies;

f.        diet (stomach content analysis).

Data management and processing

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The structure of some of the databases used in the different research institutions were presented, including procedures used to input and control the data in order to avoid erroneous information. In addition, examples of data representation were given, in particular GIS outputs. Therefore, the issues that were addressed are:

a.       structure of the data‑base;

b.       input of the data and relative control;

c.       management of data;

d.       GIS representations.

Participation

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The seminar was open to technicians and researchers belonging to Institutes and/or organizations from countries involved in MedSudMed Project. Invitation was also made to National programs coordinators, and to other regional Projects who were interested in the issue.

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