REGIONAL RESEARCH
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ACTIVITIES
REGIONAL RESEARCH |
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| Updated on 31/05/2005 |
This summarizes the work carried out by the program "CORY" in the framework of the FAO - COPEMED regional project to study dolphinfish fishery in Central-Western Mediterranean during 2000-2001 fishing seasons. It is the first joint analysis for the Mediterranean dolphinfish. The tasks carried out under the program were directed towards the collection of data for studies on the biology and fleet dynamics, on effort and catch levels, the estimation of the catch length composition and catch-at-age data. A considerable improvement on the knowledge of the biology of the species and the characterization of the fishing activity and exploitation was achieved. A preliminary assessment was carried out as an attempt to provide guidance on the management of dolphinfish in Mediterranean waters. In March 2004, a document with the last revision of our last year results and SCSA assessment sheets were presented to the SAC Subcommittee on Stock Assessment meeting. It was very welcome and all the group recommended to continue with the study of this very specific and peculiar fishery. Encouraged by the welcome received at the Subcommittee meting, COPEMED decided to set a new activity. A new Pilot Study is presently running to deepen the analysis of this fishery which has significant features such as: being mono-specific, targeted by a well defined type of fleet in a specific area of western-central Mediterranean. This pilot study is focused on the application of Operational Units concept. Its first goal is the identification and characterization of the Operational Units involved in three countries (Spain, Tunisia an Italy) sharing the species, and on the long term, to test alternative management measures based on effort control by Operational Unit . The work started at the beginning of the fishing season in August 2004 and was finished in March 2005. A workshop was held in Malta in July 2004 to draft the sampling schemes and the data management system.
Table of Contents:
The proposed objectives were:
Participants:
During the three years of life of this program, several training activities have been organized: three of them as part of the workshops held to coordinate and to analyse on going work and one more specific only for training. 1 - Sampling scheme During the first workshop held in Majorca in July 2000, an important part of the time was employed in organising sampling scheme. The sampling strata were chosen, and the protocols for biological sampling, length frequency elaboration and effort estimation were settled. Standard forms to try to more accurately estimate effort was distributed among the participants. This training was completed with a field visit to Malta and Tunisia by Dr.Cannizzaro and Dr.B.Morales-Nin, during the 2000’fishing season.
2 - Fish ageing: otholith reading In January-February 2001, a specific practical course on ageing
methodology was
First step of the workshop was to discuss current methodologies and
to consult the
bibliography related to dolphinfish ageing. A protocol was prepared
and distributed to
facilitate the transfer of methodologies. Arrangements were made to
organise the
work and the rest of the time (one and a half weeks) was devoted to
practical
exercises in the laboratory.
The report of the
workshop and the manual are available in the
Documents section of this page. 3 - Stock Assessment Data gathered were analysed during a second workshop (Barcelona - Spain, July 2002). This workshop included an important training component: a revision of main concepts and assumptions of populations dynamics models was done, in particular the different variants of Virtual Population Analysis models, with emphasis on their methodological features. Some gaps in the information were still found and it was agreed that these data would be collected in the 2002-2003 fishing season. In the final workshop (Mazara del Vallo - Italy, April 2003) practical hands on exercise was carried out in preparing the data files and running the programmes. An in deep discussion of results was also carried out to obtain the final conclusions of the study. The preliminary population analysis was carried out and completed by Dra.M.Azevedo.
Fishing technique The fishing operation consists on detection of fish under Fishing Attracting Devices (FADs) by means of visualization or using a hand line, followed by the net deployment around the FAD. The FADs consist of a float with some palm grounds or bush branches tied on top for location and below to increase their surface. The composition and form of the FAD differ, from the traditional of palms or cork to a group of tires. The material is selected for its capability to float at some centimetres below the surface. They are moored using a lime stone for anchorage. The FADs are placed in lines, in some areas there are more than one line by boat. The number of FADs moored by each boat depends of the country and also of the location of the mooring line. The net used is a special surrounding net without a purse-line, which is not very deep and almost rectangular. The particular design of this net, with a central codend in the form of a spoon and two lateral wings, made it possible to retain the shoal of fish when the two wings were hauled up from the boat at the same time. For instance, the Majorcan net in average has a 180 m length and a height of 16 m, and enclosed a maximum amount of seawater of around 46·103 m3.The net characteristics require calm weather, being the operation impossible when there are currents or rough seas. Generally the fishing operations are carried out at sunrise or sundown. Regarding the boat dimensions they are small to medium size small scale fleet, with no clear tendencies on the variation of sizes by area although there is diversity in sizes depending of the considered stratum. Some of the smaller boats are engaged in fisheries close to the coast, while others off dolphinfish season carry out fisheries such as longline and drifting net that require bigger more powerful boats. The available data showed that the fleet is relatively old with boats older than 10 years. Each boat has a mooring area that generally is sorted at the beginning of the season. The mooring areas of each boat can cover a much extended surface going from shallow waters to the slope. For instance in Majorca they are placed off 70m depth and can reach the 1200m isobath. After fishing in the mooring areas the fishermen might look for drifting floating objects and if dolphinfish are located they are captured. It could be a common practice to fish in FADs not belonging to the fishermen. The number of visited FADs each day depends of weather conditions and of the abundance of fish. From data available on Majorca it is known that an important number of FADs is lost during the fishing season (up to 70%), replacement takes place indicating that the number of FADs deployed at a given moment could be quite variable.
The catches started by regulation on the second half of August ending in December with the bulk of the catch on September and October. However, in Tunisia and Sicily there are catches in July and in this zone the fishing period might last until January. The best measure of effort in this fishery should be the number of FADs visited/day. This is very difficult to assess with the available data. The number of FAs visited each trip depends on the catch, the fishing operation stopping when the amount is sufficient. Thus, depending of the success of the first fishing operations, most FADs are visited or part of them are not inspected. The fishermen can choose a part of the mooring area for fishing considering wind and current conditions and pre-estimating the place with best capture probability. Always the hauls are carried out after the fish has been detected using a trolling line. Thus, the number of hauls is dependent of the biomass of dolphin-fish present beneath the FADs. However, there is some information about effort considering the number of boats licensed and observations of days fished.
There were catch data series for three areas but not for Sicily where only data for 3 years were available.
The measures of effort were very scarce; being only available a time series of number of boats for Malta and another for Majorca. The final report of the program is available in the Documents section of this page.
Structure: genetic analysis The study was initiated by a genetic analysis of the homogeneity of the species in the four areas carried out by the University of Girona (UG). Malta and Tunisia biologists obtained flesh samples following a protocol prepared by the UG, frozen them and these were later send to Girona to be analysed. The results showed that there is a single population in the area, thus allowing analysing globally this highly migratory species. The report of the analysis is available in the Documents section of this page.
Virtual Population Analysis (VPA) models have been used in order to assess the stock, but the results from this preliminary assessment should be interpreted with caution, because of the lack of data. These results indicate that in 2001 mortality rates might have been too high between August and October. This stock is highly dependent on the recruitment strength and little is known about the dynamics of large size and older individuals. The stock assessment forms presented in 2004 to sub-committee on Stock Assessment (SCSA) of the GFCM Scientific committee (SAC) are available in the Documents section of this page.
Regulations in force Majorca: The fishing season is regulated by the time of FADs mooring (15th August) and by the obligation of the registered boats to fish only for dolphinfish during the fishing season. The mooring areas must be off the 70 m isobath.There is a time closure around 14 h during weekends. Tunisia: no regulation in force. Currently some legislative measures are under survey to rationalize the management of this resource Sicily: no regulation in force Malta: The fishing season
extends from September to November. In May, fishermen apply for
allocation of a fishing site and obtain a license. The sites start
from 7 miles offshore at intervals of one half or three quarters of
a mile depending on the district. Management objectives This fishery is based on age 0 (between 2 and 8 months of life fish), thus depending of the annual recruitment which can be very variable. This highly migratory middle size pelagic fish seems to be a single stock in the central-western Mediterranean and should be managed together. The measure of effort is difficult because the number of FADs and their permanence on the mooring places is very important, as it is related to the number of boats both measures have to be taken into account. Sicily and Tunisia have the less regulated fishery starting the catches very soon on small fishes. A postponing of their fishery opening should be envisaged.
Management recommendations Temporal closures: the fishery should not be open before middle August. Effort limitation: the number of FADS by boat should be regulated. Minimum size The fish landed have a high price but opening the fishery in July causes that 15 cm fish are caught. Technical steps concerning gear: the pelagic long lines capture reproductive adults of the species. Quotas Market This is a seasonal fishery, efforts should be dedicated to avoid very big catches causing prices to drop. Moreover, some processing to stabilise the market should be envisaged.
In March 2004, assessment sheets were presented to the GFCM - SAC Subcommittee on Stock Assessment meeting (see documents section on this page). Encouraged by the welcome received, COPEMED decided to finance a new activity. The first objective of this pilot study the identification and characterization of the Fishery Operational Units targeting dolphin Fish in Malta, Italy, Spain and Tunisia. On the long term, the objective is to test alternative management measures based on effort control by Operational Unit. The work started at the beginning of the fishing season in August 2004 and is planned to finish in March 2005. A workshop was held in Malta in July 2004 to draft the sampling schemes and the data management system. A specific page will be added to COPEMED WEB site in order to present this new activity.
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FAO - FIGIS Species Fact Sheets - Coryphaena hippurus | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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