ICES CM 2008/K:15 Statistical Species Characterization of Gurnard

Home , Grey gurnard, Lepidotrigla, Piper gurnard, Red gurnard, Triglidae, Tub gurnard

Not to be cited without prior reference to the author ICES CM 2008/K:15

Statistical Species characterization of Gurnard Landings in North of Portugal

Feijó, D. (1), Rocha A. (2), Santos, P. (2), Saborido-Rey, F (3)

(1) Fisheries Laboratory, INRB / IPIMAR Matosinhos, Matosinhos, Portugal. [email protected] (corresponding author) (2) Science Faculty of Oporto University, Porto, Portugal (3) Spanish National Research Council, Institute of Marine Research, CSIC, Vigo, Spain

Available ICES statistics concerning gurnards are not accurate because they are often not sorted by species when they are landed, usually ending up classified under one generic category of “gurnards”. For example, France has only reported “tub gurnard” (Chelidonichthys lucernus) since 1983 and Denmark, the Netherlands and Portugal since 2000. It is obvious that statistics are incomplete for most years, in ICES Divisions and when statistic exists, they are mainly available for all species of gurnards combined and not for a specific gurnard. Concerning this problem, gurnard landings were observed in Trawler (2007) and in Artisanal Fleets (March-July 2007) in Matosinhos, Portugal. The correspondence between the common designations given at the auction market (“Ruivo” and “Cabra-Cabaço”) and the scientific name of the various species is one more problem regarding the landing statistics. The proportion, in which the various gurnard species occurred in landings, was calculated and these results compared with the official data and available bibliography. In both Fleets, the most abundant species were Chelidonichthys lucernus, Aspitrigla cuculus and C. obscurus. Other commercial species, like Eutrigla gurnardus, Trigla lyra and C. lastoviza occurred in residual amounts. Also the common designation of these species were given, at the auction market, reflects the average size of the individuals in the box sampled rather than the scientific names. Therefore, data based on the official classification does not seem to be of much scientific or statistic use for fishery assessment of these species and further studies are required for gurnards.

Keywords: Gurnards, Fishery Assessment, Fish Stocks, Sampling and Statistics.

Contact author Diana Feijó: Fisheries Laboratory, INRB/IPIMAR Matosinhos, Av. General Norton de Matos, 4; 4450-208 Matosinhos, Portugal. (Tel: +351 22 939 69 40; Fax: +351 22 937 56 49; e-mail: [email protected]).

Not to be cited without prior reference to the author ICES CM 2008/K:15

INTRODUTION

Gurnards are fishes belonging to the Triglidæ family (order: Scorpaeniformes). There are over 100 species (FISHBASE, 2007), 8 occurring in portuguese waters (Borges & Olim, 2006). They occur in all temperate and tropical seas, in depths up to 700 m (FISHBASE, 2007). They are benthonic, in rocky, muddy or sandy bottoms and their diet consists of small fish, crustaceans, gastropods and molluscs (Fischer, 1981; Bauchot, 1987; Campos, 1982). Their heads are bony and casquelike. The pectoral fins have their lower 2 or 3 rays enlarged for food detection and locomotion (Fischer, 1981).

Gurnards are considered by-catch in bottom trawl and in Artisanal gears, like beam trawl and trammel nets (Borges & Olim, 2006), although due to decrease of traditionally targeted species their interest and value has increased (Fischer, 1981, Boudaya et al., 2007).

In portuguese official data from Directorate-General Fisheries and Aquaculture (Rocha, 2007), all gurnards are classified under these designations: Tub gurnard (Trigla lucerna or C. lucernus), Gurnard nep. (Trigla spp.) and Large-scaled gurnard (Lepidotrigla cavillone) (Table 1).

In Portugal and especially in Matosinhos, landings are a mix of the 6 species found in Portuguese waters: Tub gurnard (C. lucernus), Red gurnard (Aspitrigla cuculus or Chelidonichthys cululus), Longfin gurnard (Chelidonichthys obscurus or Aspitrigla Not to be cited without prior reference to the author ICES CM 2008/K:15

obscura), Grey gurnard (Eutrigla gurnardus), Piper gurnard (Trigla lyra) and Streaked gurnard (Chelidonichthys lastoviza or Trigloporus lastoviza) (Rocha, 2007). L. cavillone (like L. dieuzeidei, also caught in the Portuguese waters) is too small to be of any commercial value and is discarded in sea. Official data does not reflect any of these facts.

Table 1. Gurnard’s official landings in fish auction market, in Matosinhos, Portugal, between the periods of 2000-2006, from Directorate-General Fisheries and Aquaculture (in Rocha, 2007). GEAR TYPE COMMON NAME CIENTIFIC NAME 2001 2002 2003 2004 2005 2006 Cabra cabaço Trigla lucerna 47 Bottom trawl Cabras nep Trigla spp. 56.030 33.079 19.443 22.998 14.281 12.117 Ruivo Lepidotrigla cavillone 24.009 14.950 13.796 11.275 7.217 5.072 Total (in kg) 80.039 48.029 33.239 34.273 21.546 17.188 Cabra cabaço Trigla lucerna 19 616 Artisanal Cabras nep Trigla spp. 12.357 13.505 11.444 10.286 9.723 10.282 gears Ruivo Lepidotrigla cavillone 60.661 84.162 64.206 55.339 63.970 59.282 Total (in kg) 73.018 97.667 75.649 65.626 73.711 70.180 Total (in kg) 153.056 145.703 109.236 99.898 95.257 87.369

This study was carried out because IPIMAR has the responsibility for fish stock assessment and there is a lack of studies concerning gurnards in Portugal. The various gurnard species are classified, in the official portuguese statistics, only under one common designation (“Ruivo”). However, in a fish auction market, they can receive various other designations (being, in Matosinhos, “Ruivo”, “Cabra-Cabaço” and, in the bottom trawl landings, “Cabra” as well). The purpose of those designations is in acquiring different and higher prices in auction. Therefore, total gurnard captures are not accounted in the official statistics and there is no information on each species’ captures.

MATERIAL AND METHODS

Sampling took place in Matosinhos Fish auction market and IPIMAR’s Fisheries Lab. Between March to July of 2007, from the Artisanal Fleet, 3 vessels were chosen each week. Among their landings, Gurnard boxes identified as “Ruivo” or “Cabra-Cabaço” was selected. Monthy, 2 samples identified as “Cabras” were collect from 1 vessel in Not to be cited without prior reference to the author ICES CM 2008/K:15

Bottom Trawl Fleet, during 2007. The commercial designation is responsibility of Fish Auction Market, regardless of boxes content. The gurnard box content was separated by species. Species identification was done with IPIMAR keys (Campos, 2002; Martins et al., 2005). Each individual was measured to the nearest lowest cm (TL) and the total weight per species (precision = 10g), on each sampled box. Statistical analyses have been made, comparing results with official data.

RESULTS and DISCUTION

In Bottom Trawl Fleet, 24 samples of Gurnards boxes (“Cabras”) were made, from 10 vessels of Bottom Trawl Fleet. In this Fleet, in general, is observed 2 commercial designations: “Cabras” and “Ruivo”, this last has a residual presence, therefore not sampled. A total of 1965 individuals were sampled with a total weight of 223,991 kg. A. cuculus (43%), C. lucernus (35%) and C. obscurus (18%) were the most abundant species. E. gurnardus, C. lastoviza and T. lyra were also present, in residual quantities (table 2). No Lepidotriglas spp. was observed.

Table 2. Species composition, in gurnard’s samples, from Bottom trawl Fleet in Matosinhos, Portugal

(Species, Percentage, N = number of individuals; W = total weight/specie (kg); Lmin = minimum length,

Lmax = maximum length; Lmed= average length).

Species % N W Lmin Lmax Lmed A. cuculus 43% 842 90,438 32,3 16,7 22,8 C. obscurus 18% 359 40,752 30,0 18,6 23,3 C. lastoviza 0% 3 0,451 24,5 21,7 23,4 E. gurnardus 3% 56 7,197 37,0 10,6 24,0 C. lastoviza 0% 5 0,601 24,7 19,3 21,9 T.lyra 1% 22 4,503 35,1 24,0 28,4 C. lucernus 35% 678 80,048 36,3 7,2 22,8 Total 100% 1965 223,991 24,5 24,0 23,8

In sampling period, the smallest sample had 4,174 kg (October) and the biggest 13,219 kg (August). Concerning species composition, we observed throughout all year the presence of Red gurnard (A. cuculus). Tub gurnard and Longfin gurnard (C. obscurus) Not to be cited without prior reference to the author ICES CM 2008/K:15

were the next most important presences (Fig .1). Individual average size is 23,8 cm, yet there were observed fish with 37 cm length.

Species Composition

25 C. lucernus T.lyra 20 C. lastoviza E. gurnardus 15 C. lastoviza C. obscurus 10 A. cuculus Total weight (kg) weight Total

0 Jan Fev Mar Abr Mai Jun Jul Ago Set Out Nov Dez

Date

Figure 1. Gurnard species composition observed in bottow trawl fleet, in Matosinhos, Portugal, during the sampling period (2007).

Still, in opposition to official data that refers C. lucernus and L. cavillone as gurnard species landed in Matosinhos (2000), we can observe that Tub gurnard (C. lucernus) is not a usual presence in the samplings in this fleet. This could be explained either by the fact that bigger individuals are separated in boxes which attain better prices and haven’t been sampled, by the crew’s use (for meals) or the direct sales to restaurants.

Sample Composition

Dez Nov Out A. cuculus Set C. obscurus Ago C. lastoviza Jul E. gurnardus Jun C. lastoviza Mai T.lyra Date (2007) Date Abr C. lucernus Mar Fev Jan

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Percentage

Figure 2. Gurnard species composition (%) observed each month, in the bottom trawl fleet, in Matosinhos, Portugal (2007).

Not to be cited without prior reference to the author ICES CM 2008/K:15

As we can observe in Figure 2, A. cuculus is present all year in the samples made. Only in October, its presence is residual when compared to C. lucernus (95%). C. lucernus, in general, is present like C. obscurus. Again, these 3 species are the most abundant in this sampling period. E. gurnardus, C. lastoviza and T. lyra were also present, in residual quantities except in January, when their abundance matched that of A. cuculus and C. lucernus.

51 samples were made in Artisanal Fleet, spanning 27 vessels (beam trawl and/or trammel nets). 98 boxes of Gurnards (W = 441,2 kg) were sampled, in a total of 1962 individuals (Table 3).

Table 3. Species composition, in gurnard’s samples, from Artisanal Fleet in Matosinhos, Portugal (Species,

Percentage, N = number of individuals; W = total weight/specie (kg); Lmin = minimum length, Lmax = maximum length; Lmed= average length (all L in cm)). Species % N W Lmin Lmax Lmed C. lucernus 39% 781 289,6 14 81 30,94 A. cuculus 29% 576 69,8 17 35 22,9 C. obscurus 30% 598 80.95 18 32 24,31 E. gurnardus 1% 24 2,5 20 29 22,09 C. lastoviza 0% 2 0,6 29 31 30 T. lyra 0% 1 0,25 - - 31 Total 100% 1982 362,75 14 81 26,87

C. lucernus, C. obscurus and A. cuculus were the most abundant species. In residual quantities, E. gurnardus, C. lastoviza and T. lyra were also present, much like as in the bottow trawl Fleet (Table 3). Individual average size is 26,9 cm, yet there were observed fish with 81 cm length (C. lucernus). This fact is important! The Artisanal fleet operates near coast and with the use of “more selective gears”, the catch have bigger individuals than the capture observed in Bottom Trawl Fleet.

We observed C. lucernus and C. obscurus mostly as "Ruivo". They were the largest species. A. cuculus was smaller and mostly classified as "Cabra-Cabaço". This common designation was given, at the auction market, to separate species and individual size - a size category from T1, the largest individuals, to T4, the smaller ones (Rocha, 2007). Not to be cited without prior reference to the author ICES CM 2008/K:15

On “Ruivo” boxes T1 and T2, C. lucernus is the only specie present. Boxes T3 contained a mixture of C. lucernus (43,59%), A. cuculus (11,47%) and C. obscurus (44,93%). C. obscurus is the most abundant on sizes T4 (79,08%). “Cabra-Cabaço” boxes of the larger sizes (T1 and T2) were rare, and therefore, only a T2 box was sampled, containing A. cuculus (95,65%) and C. lucernus (4,35%). On sizes T3 and T4, A. cuculus was the most abundant species (around 60% in both sizes), followed by C. lucernus (T3 = 10,78%; T4 = 15,94%) and C. obscurus (T3 = 24,03%; T4 = 23,90%). Other gurnard species, like E. gurnardus, T. lyra and C. lastoviza occurred in “Cabra-Cabaço” boxes, in residual amounts (Figure 4).

Figure 4. Composition of the Artisanal boxes of each designation, “Ruivo” and “Cabra-Cabaço” according to the size (T1 for bigger fish to T4 for smaller fish).

There was little difference in “Ruivo” T3/T4 and “Cabra-Cabaço” T3/T4 as far as sizes were concerned. C. obscurus and A. cuculus seemed to receive this classification randomly, based on their sizes rather than their scientific name. This confirms that primary objective is acquiring higher prices, in auction, in the time of given a specific common name to landings (table 4).

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Table 4. Average lengths (cm) in each designation, per size categories and per species for Triglidae sold in the Matosinhos auction market, in Portugal.

T1 T2 T3 T4 C. lucernus. A. cuculus C. obscurus "Ruivo" 50.37 33.44 25.22 23.35 32.17 22.83 23.89 "Cabra-Cabaço" - 23.36 24.13 22.06 23.20 22.91 25.24

C. lucernus average length is bigger than C. obscurus and A. cuculus, the 2 other species most capture species. This fact is related with the Trammel net’s use and C. lucernus maximum biological size is significant bigger.

CONCLUSION

In both Fleets, the most abundant gurnards were Chelidonichthys lucernus, Aspitrigla cuculus and Chelidonichthys obscurus.

Other commercial species, like Eutrigla gurnardus, Trigla lyra and Chelidonichthys lastoviza occurred only in residual amounts.

No individual of the genus Lepidotrigla was found, during the sampling period, in spite of official data mentioning them as the dominant gurnard landing.

Also the common designation of these species were given, at the fish auction market, reflects the mean size of the individuals rather than the scientific names. Species who reach larger sizes, such as C. lucernus and C. obscurus, are usually classified, in Artisanal landings, in the Fish Auction Market as “Ruivo” and the mixture of smaller individuals is tagged as “Cabra-Cabaço”. This fact demonstrates the recognized preference in the gastronomic use of C. lucernus and therefore, its place as the most valuable gurnard in Portugal.

The Artisanal fleet operates near coast and especially with the use of Trammel nets, them catch have bigger individuals than in Bottom Trawl Fleet’s capture. This fact is important Not to be cited without prior reference to the author ICES CM 2008/K:15

because the species and length composition will depend where the sampling is done in Artisanal or Trawl Fleet.

Also this study proves that, in the fish auction market, there’s not only C. lucernus but also a mix of 6 species designated all like one – “Ruivo”. However, the official statistics for gurnard captures are based only on the former designation and, therefore, they do not represent the total captures of Gurnards and provide incomplete information on captures for each species.

Therefore, data based on the official classification does not seem to be of any scientific or statistic use for fishery assessment of these species and further studies are required for gurnards.

ACKNOWLEGMENTS

This work was only possible with the financial and technical support of the Biological Sampling National Plan (“Plano Nacional de Amostragem Biológica” - PNAB), co- financed by Data Collection Regulation (DCR/EU DG Fish).

To Dr. Graça Pestana, responsible for PNAB in IPIMAR and Dr. Fernanda Castilho, responsible for IPIMAR Matosinhos, without their support it wouldn’t be possible to accomplish this work.

Thank you for the all help given by IPIMAR Matosinhos personnel and in special to Georgina Correia (Lab Support), Paulo Castro and Emanuel Pombal (in Fish Auction Market), without themit wouldn’t be humanly possible to finish this work!

Also to Directorate-General Fisheries and Aquaculture for all statists data supplied. Not to be cited without prior reference to the author ICES CM 2008/K:15

BIBLIOGRAPHY

Bauchot, M.-L. (1987) Poissons osseux (p. 891-1421) in W. Fischer, M.L. Bauchot and M. Schneider (eds.) Fiches FAO d'identification pour les besoins de la pêche. (rev. 1). Méditerranée et mer Noire. Zone de pêche 37. Vol. II. Commission des Communautés Européennes and FAO, Rome.

Boudaya, L., Neifar, L., Taktak, A., Ghorbel, M. e Bouian, A. (2007). Diet of Chelidonichthys obscurus and Chelidonichthys lastoviza (Pisces: Triglidae) from the Gulf of Gabes (Tunisia). Journal of Applied Ichthyology, 1-8.

Campos, J. C. V. B. (2002). Estudo do Crescimento e da Ecologia Alimentar do Cabra-Cabaço (Trigla lucerna LINNAEUS, 1758) no Estuário do Rio Mondego (Portugal). Tese de Mestrado em Ecologia Aplicada, Faculdade de Ciências da Universidade do Porto, Porto. 141 pp.

Fischer, W., Bianchi, G. e Scotts, W.B. (1981) FAO species identification sheets for fishery purposes. Eastern Central Atlantic; fishing areas 34 and 47 (in part). Canada Funds-in-Trust. Ottawa, Department of Fisheries and Oceans, Canada by arrangement with the Food and Agricultural Organization of the United Nations, Vol. 4, pp. 244-245.

FAO Fisheries and Aquaculture Department (2007). The State Of World Fisheries and Aquaculture 2006. FAO. Rome. 162 pp.

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Martins, R., Morgado, C. e Chaves, C. (2005). Principais características diagnosticantes da família Triglidae. IPIMAR.

Papaconstantinou, C. (1986) The life history of rock gurnard (Trigloporus lastoviza Brunn. 1768) in the Saronikos Gulf. J. Applied Ichthyology, 2 (2):75-86.

Rocha, R. (2007) Gestão de Stocks Pesqueiros com Especial Incidência no Estudo de capturas de Ruivo e Cabras (Triglídeos). Tese de Licenciatura em Ciências e Tecnologia do Ambiente. Faculdade de Ciências da Universidade do Porto. pp. 42.

Olim, S. e Borges, T.C. (2006) Weight-Length relationships for eight species of the familie Triglidae discarded on the south coast of Portugal. Journal of Applied Ichthyology, 22:257-259.