Medits Meeting report
Kavala, the 18-20th November 1998

The Medits group met in Kavala (Greece) at the Fishery Research Institute (FRI), the 19th and 20th November 1998. This meeting was preceded by a Medits steering committee the 18th November 1998. This report presents the conclusions of the two above mentioned meetings.

The following scientists have taken part in the general meeting:

 The chairman has opened the meeting and made the apologies for some colleagues who intended to participate but were unable to join the meeting. Particularly, Prof. Relini, held back, was appointed by Prof. G. Ardizzone.

1. General information

The general co-ordinator has indicated that, despite its usefulness and its global interest, the proposal presented on the development of methodological approaches linked with the Medits programme in answer to the last FCP call of proposals will be not subject to support from the EC. A new PCP call of proposals should be published during the first quarter 1999. The steering committee has decided to prepare two new proposals. One of these projects would be devoted to the continuation of the Medits surveys with one survey in 2000 (only one year survey would be proposed to take into account the European project for a restructuring of the incitement on the fishery data collection since 2001). The other project should be turned towards the development of data analyses (cf. below).

As J. Bertrand has explained that he will not be able to continue the co-ordination of the Medits programme after 1999 due to his new position in Ifremer, the steering committee has agreed A. Souplet as general co-ordinator since 2000.

2. Preparation of the annual report 1998

The regional teams have been invited to strictly respect the schedule presented in the CC report (Rome, 03-04/07/1998) for the preparation of their contribution to the annual report 1998. Furthermore, the following conventions have been adopted to be applied in these reports. The term ‘’abundance’’ will be used as a generic one, without reference to a specific unit. In return, the expressions ‘‘index of density’’ (or density index) and ‘’biomass index’’ will be respectively reserved for the following indices:

Index of density (DI) = N/km²

Biomass index (BI) = kg/km²

So, when a value follows one of these two expressions, the unit (N/km² or kg/km²) is implicit and it may be leaved out from the text.

A common analysis of the data has been carried on by three sub-groups which worked simultaneously during this meeting. The reports of those groups will be included in the project reports. Those groups were constituted by the following scientists :

Fish group

Nicola UNGARO, Luis GIL de Sola, Andrea BELLUSCIO, Kastriot OSMANI, Giuseppe STRIPPOLI, Fabio FIORENTINO, Argyris KALLIANIOTIS, Kosmas SOFRONIDIS and Angelini ADAMIDOU.

Cephalopods group

Eugenia LEFKADITOU, Matteo MURENU, Angelique JADAUD, Maria GONZALEZ, Vidoris PAVLOS, Arnauld SOUPLET and George TSERPES.

Crustaceans group

Maria Teresa SPEDICATO, Chrissi-Yianna POLITOU, Sergio RAGONESE, Paola RINELLI, Gianfranco D'ONGHIA, Loris FIORENTINI, Pere ABELLO and Silvestro GRECO.

The deadlines for the submission of the regional reports are reminded at the end of the present one.

3. Preparation of a working group for a common analysis of the temporal variations of the Medits results (series 1994-1998)

The co-ordination committee has decided the organization of a working group during the next spring to produce a common analysis of the series 1994-1998 of the Medits data.

1. Nursery areas

The Medits data should help to answer the following question: what are the areas where the recruits are concentrated and how abondant are these recruits? From this question, the definition of length-size groups has been discussed.

Two threshold sizes have been considered: the first maturity size and the recruitment size. The recruitment size may be related to an area or to a gear (in our case the Medits gear and/or professionnal gears). A definition of cut-off values for management purpose with reference to the crustaceans is proposed below.

Cut-off values of length frequency distributions for Crustaceans, by M.T. Spedicato

Cut off sizes, as threshold values for discriminating juveniles from adults in order to evaluate the possibility of defining nursery areas for management purposes, were established for Crustaceans.

First of all, the knowledge level about the commercial activities was considered as well as the performance of the Medits gear. Then, the different biological aspects of growth and maturation patterns of the four target Crustaceans, A. antennatus, A. foliacea, N. norvegicus and P. longirostris were taken into account. The adopted criterion consisted in estimating the rightmost length class of the recruits (defined as the first age class partially or completely retained by the commercial fisheries) when the peak of recruitment occurs (discrete recruitment). In case of continuous recruitment, an average of the rightmost length classes of the recruits in different seasons was considered. Males and females were considered combined.

The resulting cut-off lengths, which represent a compromise between biological and technological aspects, are as follows:

A. antennatus 25 mm, carapace length (CL)

A. foliacea 25 mm, carapace length (CL)

N. norvegicus 25 mm, carapace length (CL)

P. longirostris 20 mm, carapace length (CL)

2. Presentation of the data

For the preparation of the graphs, the following suggestions were given:

• Length-distribution:
• Different scales (maximum length) for fish, crustaceans and cephalopods
• Grouping in one graph the data from 0 to 100 m for Loligo vulgaris, Octopus vulgaris and Sepia officinalis
• Abundance indices:
• Grouping of the data by basin in the same figure (ex. west; central and eastern Mediterranean)
• Inclusion of a straight line at the mean value level.

1. Further analysis

It has been recommanded to introduce analyses implying GLM models.

1. Progress on the project MEDITS Data Management System, by Chrissi-Yianna Politou

1. General information

The interim report of the project was accepted by the EC and the second payment arrived at the beginning of November 1998.

A presentation of the progress of the project was made by the coordinator during the visit of A. Cervantes (DG XIV delegate) to NCMR in October 1998.

The 3^rd MDMS meeting was held in Athens in October 1998.

2. Progress on the construction of the MEDITS DMS software

The construction of the DMS structure (Task 1.1) and the development of the user interface system (Task 1.2) are complete. The development of statistical analysis (Task 1.3) is also almost complete. All the density, CPUE calculations and the length distributions are complete and the user can get the results either in a file or on a printer. A query was also introduced to calculate density and CPUE separately for juveniles and adults. The implementation of length distribution charts, which was asked by the MEDITS general coordinator during the meeting of Pisa, is under development. Finally, concerning Task 1.4 (development of utilities subroutines) the addition of personnel data to the database is constructed, whereas the part of environmental data is under construction.

An important point is the need of correction and validation, inside MEDITS, of the MEDITS coding system in order to include it in its last version in the MDMS.

3. Progress on the presentation of MEDITS and MDMS site in internet

The MEDITS site has been restructured by the Italian group and new features were added. The list of scientists was completed according to the most recent printed version of the list. The reserved part of the web site currently contains only the releases of the software produced by A. Souplet and the "Background document for DGXIV Services", which the international coordinator of MEDITS asked to be added to the reserved area waiting for further decision by the Steering Committee. The reserved area became operational after the 3^rd MDMS meeting, during which the participants received their personal usernames and password. A username and password was also given for each participating institute. The opening of the reserved area required the implementation of an interactive dialog form which will enable other users (not pertaining to the MEDITS group) to submit an account request to the Steering Committee.

The following documents are needed to complete the site:

• Annual reports
• Agenda and last meeting report
• List of publications
• Papers presented by participants

The first two items are part of the reserved area, whereas the other two will complete the public area.

The inclusion of the list of scientists in the public area of the web site has given rise to some questions regarding the European Directive (95/46/EC) on the infringement on the personal data dissemination. The MDMS group has discussed this matter and concluded that in the MEDITS case the data processed are not "capable by their nature of infringing fundamental freedoms or privacy", that they are acquired with "specific, explicit and legitimate scope" and finally that the availability of the scientists list is "necessary for the legitimate scope of the responsible of the processing" (the MEDITS project). Consequently, the group decided to leave the list in its present location, and during this MEDITS meeting, to ask the MEDITS national coordinators to undertake the correction of the information given in the list and to ensure the consent of the interested persons to be in the list.

Furthermore, the group decided to ask the MEDITS international coordinator to circulate the agenda and the minutes of the general meeting of Kavala through the MEDITS web site so that the participants will check the site. Finally, the participants are asked to forward any papers concerning MEDITS in Word format (including tables and figures) in order to include them in the site.

Concerning the MDMS web site, the MDMS logo (approved in the meeting of Pisa) was included in the opening window. Moreover, the area "Presentation of the project" contains the proposal of the MDMS project to the EC, the "Download area" (restricted area) permits the download of the latest version of the database, the area "Meetings" includes the reports of the MDMS group meetings and finally, in the area "Services" a demonstration of the database forms is given. A link with the MEDITS web site is also provided.

1. Interface MEDITS – FIGIS

The Spanish group was met with the Greek group for this purpose in Athens just before the meeting of Kavala. E. Ferrandis presented the work done on this matter. His software (GIS component) can read from TA, TB, TC files and extract these to a common GIS format, which can be imported and elaborated in the GIS. This software will be developed in order to process the results of the statistical analysis. The interface will be complete after the end of January 1999.

1. Efficacy and selectivity of the Medits gear

In two presentations, L. Fiorentini, P.Y. Dremiere have given the final results of the ESMED project (cf. annex). Furthermore, P. Lembo has presented the first results from a study on the intercalibration between the Medits gear and gears used during the Italian surveys (GRUND programme). For some species, these experiments have shown differences in the efficacy between the different gears. It is expected that more consistant results from the last project should be available by the end of March 1999.

The ESMED experiments have shown new information on the selectivity of the trawl, particularly from the escapement through the first part of the net. Another important result from this project is the difference observed in the length distribution slopes for some species between the samples obtained with the Medits and the Italian professionnal gears. These results suggest variation in the gears efficacy in respect to the length of the species caught. In some cases, the number of individuals in each length class is low. In these situations, the results have to be considered mainly as a warning. Generally, this question will need to be very carefully studied further, taking into account the importance of this parameter to estimate the total mortality parameters.

Sampling trawl geometry and performance (P.Y. Dremiere)

Some transparencies have been shown to point out the possible variations in trawl geometry, which is sensitive to a number of factors among which we can emphasize:

- Influence of strong water curents on the trawl doors and net,

- Composition of the bottom which may have a significant effect on the door spread (soft bottoms give higher spreading forces to the doors than hard bottom conditions),

- Actual trawling speed, according to the measurement system used: speed on surface or speed over the ground1.

Such variations in trawl geometry can affect catching efficacy. They are taken into account in the calculations of fish density when sensors (like Scanmar) are regularly used, giving the actual swept area and trawl vertical opening, but are unfortunately only assumed if not.

2. New project on data analyses

The steering committee has considered the different queries asked to the Medits partners and the availability of the teams involved in the programme to work on the related questions. From this analysis, it has decided to push on the preparation of a new proposal aiming to analyse the Medits data able to produce knowledge on the demersal resources directly transferable to the managers. It has been underlined that the way of analyse should strongly take into account the present management schemes and their potential evolution in short term. The approaches should include a critical review of the existing stock assessment methods in view of the definition of a package of the most appropriate ones for the characterization of the demersal resources and their exploitation level in the Mediterranean sea.

The duration of this project is foreseen for one year. The partners of the Medits programme have been invited to send to the general co-ordinator by the 31/12/1998 their suggestions for a contribution in this project.

3. Following the Pisa symposium

The general co-ordinator has indicated that the preparation of the proceedings of the symposium in Pisa is in progress. The authors has been reminded to answer as soon as possible the request for a formal agreement in view of the publication of their paper in this document.

4. Miscelleaneous

The group has been informed that R. Robles, director of Fao-Copemed, intends to support a potential enlargment of the Medits programme in the Moroccan area. He will organize during the next December a meeting between the Moroccan officials and some Medits co-ordinators to assess this possibility.

The general co-ordinator has informed the assembly that a set of Medits ‘94 basic data on three species (Merluccius merluccius, Mullus barbatus and Trisopterus minutus capelanus) has been given to the FIGIS team who intends to test the crossing between biological indicators on the distribution of living resources (from the Medits data) and spatial regulation rules on fisheries along the coasts of the four European Mediterranean countries.

5. Acknowledgements

The co-ordinator has warmly thanked A. Kallianotis and the FRI team for their support and for the quality of accommodation provided to the group during the meeting. He had thanked all the participants for their very effective contribution in the meeting.

6. Summary agenda

The efficacy and selectivity of the standard trawl used for the MEDITS project was assessed by means of a series of visual observations and fishing trips.

Visual observations were done during two trips respectively realised in the Tyrrhenian and Adriatic Sea. A towed operating vehicle, equipped with a high sensitivity video camera, was used. Due to both the small dimensions of most species present in the study area and the towing speed, it was practically impossible to observe the behaviour of fish in front of the trawl. On the contrary, fish behaviour was easy to observe inside the net, especially upstream or inside the codend. Some species (e.g. Trachurus spp) showed a higher swimming resistance in comparison with others like Diplodus annularis.

Four fishing trips were done in 1996 and 1997 in different areas of the Adriatic Sea and in different seasons as to obtain results on different target species. Each trip consisted of a series of hauls, partially done with the MEDITS trawl and partially done with a typical Italian commercial trawl.

A cover codend was used on the commercial trawl in order to have the same mesh opening in the codends of the two nets. Some small net bags were mounted outside of the body of the MEDITS and the commercial trawls in order to quantify the possible escapement through the trawl bellies.

During each trip the two trawls were daily alternate, but the fishing area was kept the same. Net geometry (horizontal and vertical net opening) was measured during all the hauls. The catch data were converted to abundance per swept area before compare them among the trawls.

Efficacy comparisons were done on ten fish species, one crustacean and four molluscs belonging to the main MEDITS target species list. The MEDITS trawl showed a significant lower efficacy, both in weight and in number of individuals, than the commercial trawl on Merluccius merluccius, Solea vulgaris and Nephrops norvegicus. A highly significant difference was found in the weight, but not in the number, of Pagellus erythrinus. The two trawls showed the same efficacy on Mullus barbatus, while the MEDITS trawl resulted significantly more efficient than the commercial trawl on the number of individuals caught of Trachurus trachurus. All the other differences on main MEDITS target species resulted not significant. The comparison results confirm the general idea that the MEDITS trawl efficacy on the benthic species is low when compared with the commercial Italian one, while it seems better on the species released from the bottom.

For many species, a significant escapement occurred in the near-bottom part of the side panels of the MEDITS trawl. N. norvegicus had the highest rate of escapement (64%) which was mainly due to small size individuals. This size selection was confirmed by the catch comparison with the commercial trawl. Selectivity curves were computed for this species with a L_50% of about 21-22 mm in carapace length. The escapement of M. merluccius was not so consistent (13%), but a comparison between the size frequency distributions obtained by the two trawls showed that the MEDITS trawl was less efficient in the 30-38 cm size range. For other species (Micromesistius poutassou, P. erythrinus and Loligo vulgaris) the efficacy of the MEDITS trawl significantly decreased at large size classes. This could be explained by the ability of medium-large size individuals to escape through the belly sections of the MEDITS trawl.

The escapement of M. barbatus was very low, even though there was a great abundance of this species during the tests. M. poutassou were shown to escape mainly through the mid-height side part of the MEDITS trawl.

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