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REGIONAL RESEARCH 		Project CGP/REM/057/SPA
Updated on 31/05/2005
 

Exploitation models of the red lobster Palinurus elephas in the Mediterranean fisheries of Spain and Tunisia

Table of Contents:

 

Objectives

General objective

The objective of the Spanish-Tunisian project was to carry out comparative study of the red lobster (Palinurus elephas) fisheries in the Western Mediterranean (Baleares) and the Central Mediterranean (Tunisia), with special attention to the exploitation models in the fisheries of the two countries. The biology of the species has been also contemplated in the study as an important objective, in particular of the biological parameters relevant for management.  

The study kept on running during 2004 in five fishing areas off Tunisia (see the map in the document). Three experimental surveys were carried out to test differential selectivity indices between entangling nets and traps. Aiming at proposing eventual management options.

Specific objectives

  • Gathering of information on the fisheries: catch, effort, gears used, main harbors, etc.
     

  • Estimating yields and size structure of the populations.



 

Teams involved
   

Spanish team :

Tunisian team : 

                                        
   
 1 Instituto Español de Oceanografia (IEO)
Muelle de Poniente s/n
Apdo. 291
07080 Palma de Mallorca
España
Tel: +34 (971) 401 561 /401 877
Fax: +34 (971) 404 945
2 Institut National Agronomique de Tunisie (INAT)
Département des Pêches
43, Avenue Charles Nicolle
1082 Tunis
Tunisie
Tel: +216 (1) 336 998
Fax: +216 (1) 799 391
3 Institut National des Sciences et Technologies de la Mer (INSTM)
28, Rue 2 Mars 1934
2025 Salammbo
Tunisie
Tel: +216 (1) 735 848
Fax: +216 (1) 732 622     

 

 

Material and methods

 

The experience of the Spanish team, involved in a project on the biology and fisheries of the red lobster in the Spanish Mediterranean since 1997, as well as the financial support of the COPEMED project, contributed to the standardization of the sampling methodology and a joint comparative analysis of the results. 

Work plan

  • April 2001: workshop in Baleares, including organization of the project and demonstration of sampling methods  to the Tunisian team (field sampling, laboratory analysis and visit of fish market).

  • May 2001: workshop in Tunisia, including presentation of the project to the fishermen and on board data collection.

  • October 2001: experimental fishing survey with trammel-nets and traps in Tunisia.

  • November 2001: experimental fishing with trammel-nets in the Balearic Islands.

  • November 2002: meeting to elaborate the final report.

 

Two study areas are considered in this study: 

  1. the fishing grounds off islands in the Spanish western Mediterranean (Balearics and Columbretes),
  2. the fishing grounds off islands in northern Tunisia (La Galite and the Esquerquis). The Columbretes and La Galite Islands are marine reserves where lobster fishing is forbidden and fisheries occur in the boundaries and nearby areas.

 


Click within A or B rectangles to zoom on the fishing areas  

Data collected

Sampling program on commercial boats: a total of 130 hauls (87 from Spain, 43 from Tunisia) were sampled in 2001, during the spring and fall seasons.  Data collected were:

  • hauls characteristics,

  • catches (including bycatch),

  • sex and size from all lobsters caught,  individual size of the non-lobster catch.

Due to the impossibility of having precise individual weights on board commercial boats, length-weight relationships were calculated from research surveys conducted in the Columbretes Islands (for the Spanish data) and from Tunisian lobster pond (for the Tunisian data).

Laboratory sampling: In the laboratory, the following biological data/samples were collected: length, weight, maturity stage, gonad weight and color, gonad samples, diet information, moult stage, and samples for genetic analysis.

Logbook data covering the 2002 fishing season: 1149 hauls (468 from Spain, 681 from Tunisia) were registered. Data collected were:

  • haul characteristics (as above),

  • lobster catch (number and weight) for each fishing set.

Lobster landings from 1990 to 2002 were also collected from official Spanish and Tunisian fishery statistics.

 

Methods for data analysis

Statistical tests were used for a spatio-temporal analysis of the 2 fisheries. Non-lobster catches were used to estimate by-catch and discards.

 

Results
 

Fleets Characteristics and Fishing Grounds

The fleets from Spain and Tunisia are composed of artisanal boats with technical characteristics closely related to the distance from their homeports to the fishing ground. While in Tunisia some 60 fishing units of medium to large size (14-16 mt) engage in lobster fishing during the season, in the Spanish Mediterranean a much larger number (> 250) of small artisanal vessels fish for lobster during the main part of the fishing season. The reason for this is that in Tunisia most of the productive fishing grounds are at distances from the coast over 60 nm while in Spain fishing for lobster takes place mostly within 30 nm from the coast.  The landing strategies also differ. While in Tunisia most of the catches are landed in two harbours – Bizert and Tabarka – and are bought by “viveros” to be exported to European markets, in Spain lobster is landed in a myriad of small harbours where it is partially sold directly for fresh consumption locally.

 

Spain Tunisia
Balearic Islands Columbretes Islands La Galite & Esquerquis Islands.
Number of ports  16  4  2
Number of boats 257 5 56
Gross tonnage (GT)  2.0 ± 1.5 (0.2–11.2) 10.7 ± 3.4 (7.6–15.1) 18.9 ± 8.6 (6.8–47.0)
Horse power (HP)  37.5 ± 31.8 (3–261)  119.0 ± 35.1 (85–170)  149.4 ± 73.1 (45–330)
Boat length (m) 7.2 ± 1.7 (3.2–12.8)  12.9 ± 1.3 (11.2–14.6) 14.0 ± 2.1 (10.6–18.8)
Boat age (years) 34.8 ± 21.1 (1–98)  16.8 ± 14.1 (3–37) 13.4 ± 5.0 (2–28)
Nº fishermen/boat  2.0 ± 0.8 (1–3)  3.2 ± 0.4 (3–4)  6.1 ± 0.9 (4–7)
Soak time (days) 2.3 ± 0.9 (2–5)  4.5 ± 2.6 (2–14)  2.5±2.4 (2–10)
Trammel net length (m)  662 ± 147 (450–1250)  726 ± 234 (350–1900)  653±99 (300–850)
Mesh size (mm)  71 ± 11 (40–100)  69 ± 12 (40–80)  79 ± 3 (70–80)
Depth (m)  74.3 ± 26.9 (15.0–170.0)  79.3 ± 19.0 (26.0–172.0)  78.1±37.2 (23.0–185.0)

Table 1 -

Characteristics of the fleets and fishing operations in Spanish and Tunisian P. elephas fisheries studied. Values are means, standard deviations and ranges.


 

Spain Tunisia
Balearic Islands Columbretes Islands La Galite & Esquerquis Islands.
Distance from homeport   2-3nm     30-40nm between 40 and 60 nm
Trip duration daily 2-3 days 5-6 days
       

Table 2 - Fishing ground location of the Spanish an Tunisian fisheries

 

Regulation

Lobster fisheries are regulated in the two countries by minimum landing sizes (80 mm CL) and closed seasons (September to February). However, in Tunisia there is the possibility of closing certain areas to fishing before the end of the season if there is evidence that the stock abundance is low. It is unclear whether this measure is applied.
  

Habitat

Maërl substrates (free living cralline algae and associated zoobenthos) often associated with the brown algae Laminaria rodriguezii.

 

Catches   

Spain

Tunisia

Student´s t-test

Total

 

 

 

 

 F

94.2

72.1

N

749

172

 

W

408431.9

161312.9

%N total catch

47.75 ± 2.50

41.44 ± 5.34

NS (p=0.230)

%W total catch

41.32 ± 2.63

47.44 ± 5.80

NS (p=0.277)

Commercial catch

 

 

 

N / haul

5.87 ± 0.67

2.84 ± 0.49

**(p=0.003)

W / haul

3873.7 ± 422.9

2846.6 ± 625.7

NS (p=0.149)

%N lobster catch

70.93 ± 2.87

69.71 ± 4.80

NS (p=0.846)

%W lobster catch

81.40 ± 2.39

72.89 ± 4.95

NS (p=0.560)

‘Rotten’

 

N / haul

0.77 ± 0.15

1.02 ± 0.19

NS (p=0.313)

W / haul

400.4 ± 83.2

879.6 ± 209.2

**(p=0.006)

%N lobster catch

7.53 ± 1.43

24.18 ± 4.29 **(p<0.001)

%W lobster catch

7.15 ± 1.41

23.29 ± 4.42

**(p<0.001)

Undersized

N / haul 1.97 ± 0.29 0.14 ± 0.05

**(p<0.001)

W / haul

420.5 ± 65.4

26.6 ± 12.21

**(p<0.001)

%N lobster catch

21.54 ± 2.47 6.11 ± 3.35 **(p<0.001)
%W lobster catch

11.45 ± 1.81

3.82 ± 3.22

* (p=0.030)

Table 3 -   

Summary statistics of P. elephas catches (total and by categories) from fishing sets sampled during May and August-October 2001 in Spanish (N=87 hauls) and Tunisian (N=43 hauls) fisheries. F: frequency of appearance (%); N, W: total number and weight; %N, %W: percentage in number and in weight referred to the total catch or to the total lobster catch; N/haul, W/haul: number and weight per standardised haul.

 

Size and Sex structure of lobster catch

Tunisian exploited populations have a greater proportion of large lobsters than populations exploited by the Spanish fleets. This could indicates higher levels of exploitation in the Spanish fishery than in the Tunisian fishery.

Figure 1a - P. elephas size-frequency distributions (males and females) of the catches from the Spanish and Tunisian fisheries
    

   

Figure 1b - P. elephas size-frequency distributions (total) of the catches from the Spanis and Tunisian fisheries

 

Lobster Yields

  • Seasonal evolution

The seasonal evolution of lobster yields showed opposite trends in the two fisheries. The reason is that while Spanish vessels fish on the same ground the entire season, the Tunisian fleet fish close to the homeports at the beginning of the season and moves offshore as the weather improves. 
Figure 3a - Monthly P.elephas yields (weight) from the Spanish (black dots) and Tunisian (white dots) fisheries
   

 

Figure 3b - Monthly P.elephas yields (number) from the Spanish (black dots) and Tunisian (white dots) fisheries

 

  • Time series

Tunisian total landings showed an abrupt increase from 1990 to 1993, due to several factors, such as the growth of the fleet and unusually good weather conditions, but mainly to the discovery of new fishing grounds like the Esquerquis Islands.

Figure  4 - Evolution of the number of boats (solid line) and number of days at sea (broken line) for the lobster fleet in Tunisia

 

The depletion of both Spanish and Tunisian fisheries over the 1999-2000 period would reflect an intense exploitation.


Double-click on the graph for 100% view

Figure 5a - Monthly (solid line) and annual landings (broken line) of P.Elephas for the Tunisian fishery during 1990-2002
  


Double-click on the graph for 100% view

Figure 5b - Monthly (solid line) and annual landings (broken line) of P.Elephas in the Columbretes Islands (Spain)  fishery during 1990-2002

Figure 6a - Mean monthly evolution (mean and standard error) of P.elephas landings for the Tunisian fishery during 1990-2002

Figure 6b - Mean monthly evolution (mean and standard error) of P. elephas landings in the Columbretes Islands ( Spain ) during 1990–2002.

 

  

Documents

    

  • Rapport préliminaire des campagnes de pêche expérimentale réalisées à la Galite dans le cadre du projet Tunisio-Espagnol sur la Langouste Rouge Palinurus elephas (2001) - A. Gaamour, H. Missaoui, A. Quetglas, O. Reñones Pérez, R. Goñi Beltrán De Garizurieta, T. Zarrouk

  

Document file(s)
 190Kb

  

  • Spiny lobster (Palinurus elephas Fabricius 1787) fishery in the western Mediterranean: A comparison of Spanish and Tunisian fisheries - Submitted to the Journal Aquatic Living Resources (May 2003) - A. Quetglas, A. Gaamour, O,. Reñones, H. Missaoui, T. Zarrouk, A, Elabed, and R. Goñi.

Report
 137Kb

  • Rapport Final du projet: Les Pêcheries de la langouste rouge Palinurus elephas de la Région Nord de la Tunisie : Engin de pêche , Eléments biologiques et gestion. - Gaamour Adel, Rjeibi Okbi, Bdioui Marouène, Missaoui Hechmi, Youssef Zaraa et Jaziri Sabri.

Report
137Kb

 

 

 

 

Photos


Click on each picture that you want to see at full size.

Palinurus elephas (Marine Reserve of Columbretes Islands, western Mediterranean Tagging P. elephas for mark-recapture experiments Tagging P. elephas for mark-recapture experiments
Full size 110 k Full size 31 k Full size 28 k
Commercial artisanal vessels fishing P. elephas with trammel-nets in the Columbretes (western Mediterranean) fishing grounds. Commercial artisanal vessels fishing P. elephas with trammel-nets in the Columbretes (western Mediterranean) fishing grounds. Trap used in assessment surveys of P. elephas in the Marine Reserve of Columbretes Islands (western Mediterranean)
Full size 58 k Full size 47 k Full size 40 k

Source: EDFAM project

 

  

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