Not to be cited without prior reference to the author

International Council for CM 2004/CC: 19 the exploration of the

Theme Session on Cephalopod Stocks: Review, Analyses, Assessment, and Sustainable Management

The cephalopods in the small-scale fishery in the eastern Thracian Sea (NE Mediterranean)

E. Lefkaditou1, J. Haralabous1, D. Sarikas2, S. Karamelidou2 and S. Kavadas1

1 National Centre for Marine Research, Aghios Kosmas, Helliniko, 16604 Athens, . E-mail: teuthis @hcmr.gr 2 Fisheries Co-operative of "Evros", Fishing Port, 68100 Alexandroupolis, Greece. E-mail: [email protected]

Abstract Landings data of the Fisheries Co-operative of Alexandroupolis “Evros” for the period 1998-2002 indicate that cuttlefish (Sepia officinalis) and octopus (Octopus vulgaris) consist an important resource for the small scale fishery in the coastal zone of the eastern Thracian Sea. Cuttlefish is targeted by specific trammel nets (32-36 mm mesh size) during late winter and spring, whereas it is fished as by-catch by trammel nets targeting shrimp (Penaeus kerathurus) and sole (Solea vulgaris) in summer and autumn. Octopus is the target species of pots used mainly in autumn and by catch of trammel nets. Variation of total landings and LPUE are examined considering vessel- day as the common unit of fishing effort for all fishing gears. LPUE for gears fishing octopus and cuttlefish as by-catches is generally very low. Octopus LPUE for pots shows a seasonal peak in June, whereas the cuttlefish LPUE for specific trammel nets in March-April, both reflecting the availability of the species in the coastal fishing grounds and probably depending on the size composition of the catches. Monthly variation of total landings by gear is clearly dependent on the fishing strategy followed, as well as, on the LPUE variation of the targeted species.

Keywords: Cephalopoda, small-scale fisheries, Mediterranean.

Introduction The most commercially important cephalopod species in Greece, Octopus vulgaris, Loligo vulgaris and Sepia officinalis, are mainly targeted by inshore small-scale fisheries, which in certain areas like the Thracian Sea may contribute the major part of their total landings (Lefkaditou & Adamidou, 1997; Lefkaditou & Papaconstantinou, 1999). The artisanal fishing gears targeting cephalopods are trammel-nets of 32-36 mm mesh size for cuttlefish, beach seine for calamari, where as, for octopus pots and fyke-nets are used in different localities depending on the bottom kind. The trammel- nets are traditional gears for coastal fishery in Greek waters, different types of which are used alternatively during the gear to catch cuttlefish, shrimp and sole. The Greek beach-seine, a seine net hauled by a special winch on board of small vessels anchored within 70 m from the shore, is also a traditional fishing method exploiting large quantities of L. vulgaris especially in the western Thracian Sea (Lefkaditou & Adamidou, 1997, Lefkaditou et al., 2001). The use of plastic pots and fyke-nets for fishing octopus, on the other hand, is comparatively new having only been initiated during the last decade mainly in the Thracian Sea and is the most probable reason for the increase of octopus landings in this area (Lefkaditou & Papaconstantinou, 1999; Lefkaditou et al., 2002) According to official fisheries statistics, cephalopod landings from coastal fisheries consist an important part of total cephalopod landings (Stergiou, 1988; Lefkaditou et al., 2002) and especially those of cuttlefish and octopus. However there are no specific statistical data showing contribution of the various artisanal fishing gears. Recent investigations carried out in the Thracian Sea during the fishing period 1997- 1999 in the framework of EU research projects (COASTAL: DG XIV 96/54, DG XIV 97/54) have shown a great variability of coastal fishing activities between the different ports (Kallianiotis & Koutrakis, 1999; Lefkaditou et al., 2001). The analysis of (LPUE) data on cephalopod landings per unit of fishing effort sampled on a monthly basis for trammel-nets, beach seine and fyke-nets, indicated the necessity for long term monitoring in order to understand the dynamics of these short-living species and associated fisheries (Belcari et al., 2002; Tsangridis et al., 2002; Lefkaditou et al., 2003; Kallianiotis et al., 2004). This is an analysis of daily cephalopod landings by the fishing vessels of the Fisheries Co-operative of Alexandroupolis “Evros”, operating in the eastern Thracian Sea (Figure I), over six years. Cephalopod species landings by gears targeting them, as well as, cephalopod by-catches by trammel-nets targeting shrimp and sole, are described on a monthly basis and factors affecting variability of species landings per vessel-day are discussed.

Materials and Methods Daily landings of cephalopod species, as well as, of two more species consisting main targets of trammel-net fishery (Solea vulgaris and Penaeus kerathurus) were extracted from the sales data base of the Fisheries Co-operative of Alexandroupolis “Evros”, for the period April 1998 – December 2003. Fishing gear for each vessel and day was assigned taking into account the targeted species showing the highest catch in each vessel-day. Contribution of cephalopod species in the total landings by year was calculated from the annual data on species sales held by the Fisheries Cooperative. For cuttlefish and octopus consisting over 99% of cephalopod landings, fishing effort was estimated by month and fishing gear, as the total of vessel-days recorded. For the gears that these species were secondary catches, only vessel-days with cephalopod landings were counted. The average monthly LPUE was estimated by gear from the total weight in kilograms of cuttlefish or octopus landed per month divided by the monthly effort deployed by gear for each of the species respectively. To investigate factors affecting variation of species landings by vessel day (LPUE) recorded during the period studied, the GLM ANOVA using the SPSS version II software program for Windows, was applied for each gear and species. As main factors in the present ANOVA were considered year and months as strata within year. In case of the fishing gears catching octopus and/or cuttlefish as secondary species, the effect of the target species landings was examined as a covariate. Possible interactions between factors and covariates were also examined. The type IV for Sums of Squares was selected in the GLM analysis because the following two conditions were met: a) the design of the data sets used was not balanced, since there was not the same number of cases in each combination of the factors (unbalanced cells) and b) at certain combinations of months and years there were no records (missing cells). (Levins test for equality of variances was used)

Results The main gears catching cephalopods in the eastern Thracian Sea are trammel-nets with 32-36 mm mesh size from knot to knot targeting cuttlefish (so-called Sepia- Nets), plastic pots with opening diameter 14cm targeting octopus, as well as, trammel-nets targeting soles (so-called Sole-Nets) and shrimps (so-called Shrimp- Nets) with mesh sizes 34-40 mm and 21-23 mm from knot to knot respectively. Fyke-nets targeting octopus or cuttlefish are used by a limited number of vessels and are excluded from the present analyses due to the very low number of records.

Table I. Annual landings of S.officinalis, O.vulgaris, L. vulgaris, E. moschata and total fish from small-scale marine fisheries, transacted through the Fisheries Co-operative of Alexandroupolis “Evros”, during the period April 1998 – December 2003. Sepia Octopus Loligo Eledone Cephalopod Total Year officinalis vulgaris vulgaris moschata landings landings 1998 45.46 47.06 0.05 0.02 92.58 231.54 1999 70.64 25.35 0.07 0.02 96.08 272.75 2000 60.52 17.27 0.09 0.23 78.11 210.86 2001 73.86 19.10 0.05 0.08 93.08 244.10 2002 53.45 19.87 0.11 0.01 73.43 179.96 2003 23.66 34.47 0.06 0.09 57.28

Table II. Percentage contribution of fishing gears operating in the Thracian Sea in cuttlefish and octopus landings for the years 1998-2003.

S. officinalis landings % O. vulgaris landings % Year Sepia- Shrimp- Sole- Other Pots Sepia- Shrimp- Sole- Other Nets Nets Nets gears Nets Nets Nets gears

1998 82.17 12.41 4.55 0.87 97.12 0.81 0.60 1.19 0.29 1999 91.35 8.28 0.26 0.11 96.42 2.21 0.44 0.50 0.44 2000 95.35 3.98 0.45 0.22 91.60 5.09 0.82 1.30 1.19 2001 96.25 3.01 0.51 0.23 90.18 7.47 1.08 0.90 0.38 2002 92.05 7.09 0.49 0.38 88.49 7.60 1.84 1.52 0.54 2003 96.65 2.69 0.48 0.18 96.30 1.27 0.50 1.65 0.29 A total of 99 fishing vessels sold their fish through the Fisheries Co-operative of Alexandroupolis “Evros”, during the period April 1998 – December 2003. All vessels practised trammel-net fishery but only 66 used pots. The cephalopod species landed included Sepia officinalis, Octopus vulgaris, Loligo vulgaris and Eledone moschata, the latter two of which did not exceeded 0.5 % of the cephalopod landings in any of the years examined (Table I). So further analyses concern only cuttlefish and octopus. The contribution of the different fishing gears in the annual landings of cuttlefish and octopus are presented in Table II. Pots and Sepia-Nets targeting correspondingly octopus and cuttlefish contribute the major part (>80%) of their landings. Among trammel nets catching cephalopods as secondary species, Shrimp-Nets catch highest quantities of cuttlefish, where as, octopus is mostly caught by Sepia-Nets. Plotting of the number of vessels-days by species and fishing gear for every month during the period examined (Figure 2) shows clearly the seasonal character of trammel-net fisheries targeting different species. Trammel-nets targeting cuttlefish are used from February to early June with peak in March-April. Shrimp-Nets begin in late April, peak in May-June and are used till mid of autumn. Sole-Nets are used during all the year round but by the highest number of vessels in September - October when the availability of the other two species targeted by trammel-nets is decreasing in the coastal fishing grounds. Octopus is caught quite frequently (~1/3 of vessel-days) by Sepia-nets, but less frequently than cuttlefish by Shrimp-Nets and Sole-Nets. Cuttlefish by-caches are met more frequently in Shrimp-Nets (~35% of vessel-days) than in Sole-Nets (~20% of vessel-days). Average landings per vessel-day (Figure 3) are apparently higher for the gears targeting octopus or cuttlefish, for which higher annual oscillation is also noted. The monthly evolution of average cuttlefish LPUE for Sepia-Nets seems to follow the same pattern with fishing effort, showing that the seasonal abundance of the species in the coastal fishing grounds is designating strategy of the trammel-neters. Cuttlefish by catches of Shrimp-Nets are decreasing from April to September. During late summer and autumn lower cuttlefish by-catches are also observed in Sole-Nets. Octopus average landings per vessel-day from pots increase during summer, revealing remarkably higher values in the years 1999-2001. Octopus by-catches landed by trammel-net fisheries are generally quite low and no clear trend is evident except in case of Shrimp-Net by-catches that show clearly a seasonal trend with lower values from July to September.

Table III. Results of GLM ANOVA performed on octopus LPUE (kg/vessel-day) by pots, recorded in the eastern Thracian Sea from April 1998 to December 2003.

Tests of Between-Subjects Effects Dependent Variable: O.vulgaris Type IV Sum Source of Squares df Mean Square F Sig. Model 11710708.080a 70 167295.830 29.791 .000 YEAR 5535518.051 6 922586.342 164.286 .000 MONTH(YEAR) 3688757.690 64 57636.839 10.263 .000 Error 13741678.170 2447 5615.725 Total 25452386.250 2517 a. R Squared = .460 (Adjusted R Squared = .445)

The GLM ANOVA fitted on LPUE from fishing gears targeting octopus and cuttlefish confirmed the importance of year and month within each year, accounting for 46% and 55% of the corresponding variability (Tables III and IV). In cases of octopus by-catches the fitted models explained better the observed variability (r2: 0.68-0.77) revealing the significance of covariant target species landings in addition to the effects of year and month (Tables V, VI, VII) for all three types of trammel-nets. The variability of Shrimp-Nets by-catches of cuttlefish seems to depend mainly on year and month within years not affected by shrimp LPUE (Table VIII), whereas, in case of Sole-Nets by-catches month within year was significant only in interaction with sole LPUE (Table IX).

Table IV. Results of GLM ANOVA performed on cuttlefish LPUE (kg/vessel-day ) by Sepia-Nets, recorded in the eastern Thracian Sea from April 1998 to December 2003.

Tests of Between-Subjects Effects Dependent Variable: S.officinalis Type IV Sum Source of Squares df Mean Square F Sig. Model 11919183.700a 34 350564.226 250.771 .000 YEAR 1395693.970 6 232615.662 166.398 .000 MONTH(YEAR) 535634.774 28 19129.813 13.684 .000 Error 9724095.710 6956 1397.944 Total 21643279.410 6990 a. R Squared = .551 (Adjusted R Squared = .549)

Table V. Results of GLM ANOVA performed on octopus LPUE (kg/vessel-day) by Sepia-Nets, recorded in the eastern Thracian Sea from April 1998 to December 2003. Tests of Between-Subjects Effects Dependent Variable: O.vulgaris Type IV Sum Source of Squares df Mean Square F Sig. Model 16640.143a 55 302.548 53.958 .000 YEAR 885.067 6 147.511 26.308 .000 MONTH(YEAR) 199.018 21 9.477 1.690 .026 CUTTLE 31.504 1 31.504 5.619 .018 YEAR * CUTTLE 10.447 5 2.089 .373 .868 MONTH * CUTTLE(YEAR) 453.263 21 21.584 3.849 .000 Error 7911.677 1411 5.607 Total 24551.820 1466 a. R Squared = .678 (Adjusted R Squared = .665)

Table VI. Results of GLM ANOVA performed on octopus LPUE (kg/vessel-day) by Shrimp-Nets, recorded in the eastern Thracian Sea from April 1998 to December 2003.

Tests of Between-Subjects Effects Dependent Variable: O.vulgaris Type IV Sum Source of Squares df Mean Square F Sig. Model 2150.027a 58 37.069 28.693 .000 YEAR 148.686 6 24.781 19.182 .000 MONTH(YEAR) 27.411 23 1.192 .922 .568 SHRIMPS .689 1 .689 .533 .466 YEAR * SHRIMPS 4.084 5 .817 .632 .675 MONTH * SHRIMPS(YEAR) 15.905 23 .692 .535 .964 Error 758.353 587 1.292 Total 2908.380 645 a. R Squared = .739 (Adjusted R Squared = .713)

Table VII. Results of GLM ANOVA performed on octopus LPUE (kg/vessel-day) by Sole-Nets, recorded in the eastern Thracian Sea from April 1998 to December 2003.

Tests of Between-Subjects Effects Dependent Variable: O.vulgaris Type IV Sum Source of Squares df Mean Square F Sig. Model 4192.879a 104 40.316 22.583 .000 YEAR 199.319 6 33.220 18.608 .000 MONTH(YEAR) 85.415 44 1.941 1.087 .326 SOLES 3.318 1 3.318 1.859 .173 YEAR * SOLES 9.967 5 1.993 1.117 .350 MONTH * SOLES(YEAR) 109.666 44 2.492 1.396 .049 Error 1253.261 702 1.785 Total 5446.140 806 a. R Squared = .770 (Adjusted R Squared = .736)

Table VIII. Results of GLM ANOVA performed on cuttlefish LPUE (kg/vessel-day) by Shrimp-Nets, recorded in the eastern Thracian Sea from April 1998 to December 2003. Tests of Between-Subjects Effects Dependent Variable: S.officinalis Type IV Sum Source of Squares df Mean Square F Sig. Model 65852.624a 51 1291.228 145.298 .000 YEAR 2139.428 6 356.571 40.124 .000 MONTH(YEAR) 438.529 19 23.080 2.597 .000 SHRIMPS 2.858 1 2.858 .322 .571 YEAR * SHRIMPS 12.108 5 2.422 .273 .928 MONTH * SHRIMPS(YEAR) 213.222 19 11.222 1.263 .197 Error 40096.966 4512 8.887 Total 105949.590 4563 a. R Squared = .622 (Adjusted R Squared = .617)

Table IX. Results of GLM ANOVA performed on octopus LPUE (kg/vessel-day) by Shrimp-Nets, recorded in the eastern Thracian Sea from April 1998 to December 2003.

Tests of Between-Subjects Effects Dependent Variable: S.officinalis Type IV Sum Source of Squares df Mean Square F Sig. Model 8894.723a 117 76.023 16.697 .000 YEAR 324.193 6 54.032 11.867 .000 MONTH(YEAR) 220.268 50 4.405 .968 .539 SOLES .323 1 .323 .071 .790 YEAR * SOLES 10.370 5 2.074 .456 .809 MONTH * SOLES(YEAR) 348.272 50 6.965 1.530 .013 Error 2918.497 641 4.553 Total 11813.220 758 a. R Squared = .753 (Adjusted R Squared = .708)

Discussion Cephalopods contribution in the coastal fishery practised by the Fisheries Co- operative of Alexandroupolis “Evros” in the Eastern Thracian Sea ranges between 35- 41 % in landings, percentage considerably higher than that given by National Statistical Service of Greece (NSSG) for artisanal fishery in Greek waters (7-15%). This could be attributed to the higher abundance of cephalopods in the Thracian Sea as indicated by the generally high annual production of cephalopods observed in this (Lefkaditou et al., 2002) during the last decade, as well as, to the development of new more effective fishing methods for octopus exploitation. Octopus and cuttlefish, targeted by specific gears, represent the major part of cephalopod landings revealing the relatively high abundance of these species in coastal shallow waters. However the quite lower landings of calamary are most probably due to the lack of beach-seine which mainly exploits it in the western Thracian Sea (Lefkaditou & Adamidou 1997; Lefkaditou et al., 2001) but cannot operate in the eastern region because of the very low bottom inclination (Lefkaditou et al., 1998). The seasonal pattern observed in cuttlefish LPUE by Sepia-Nets is common in different areas of the (Belcari et al., 2002) related to the seasonal inshore migration of this species during early spring for reproduction. This seems to be the reason also for the decreasing trend of Shrimp-Net and Sole-Net by-catches of cuttlefish per vessel-day from April to September. Effort deployed by the different types of trammel-nets seems to follow the targeting species abundance in the coastal zone reflected by the trend of relevant LPUE. On the contrary, trend of octopus pots fishing effort does not coincide with LPUE trend. The peak of octopus LPUE by pots in early summer and the following decline, is in accordance with results for fyke-nets used in the western Thracian Sea (Kallianiotis et al., 2004). Octopus fishery with clay-pots in the western Mediterranean (Sanchez & Obarti), as well as, trap fishery in the SE Atlantic coasts (Hernandez-Garcia et al., 1998) have revealed two seasonal peaks of CPUE, in spring and autumn. The absence of a second peak in autumn in the studied area could be probably related to the highly increased effort in autumn, or to a different reproductive pattern of the species in the Eastern Mediterranean Sea. Availability of octopus in the fishing grounds is reduced during spawning season due probably to migration to deeper waters as suggested by Mangold (1983) or just to the avoidance of frequently removed pots during the spawning season (Kallianiotis et al., 2001). The variation of octopus and cuttlefish LPUE by respective specific gears targeting these species, is not explained quite satisfactory by the GLM ANOVA, that may be attributed to the lack of more detailed effort data referring to the length of Sepia-Nets and the number of pots used. In case of octopus and cuttlefish by-catches the results of the fitted models were better due most probably to the inclusion of the target species landings covariate reflecting in a way the effort deployed. Conflicts among fishermen for the use of different and especially the recently expanded fishing gears in the coastal zone make urgent the need for a systematic study of the effectiveness of each gear, as well as, of their effect on stocks and their contribution in the total fishery landings and sales at a regional level, so that a management scheme for an harmonic combination of the different coastal fishing activities and sustainability of the resource to be achieved.

References Belcari P., Sartor P., Sanchez P., Demestre M., Tsangridis A., Leondarakis P., Lefkaditou E. & C. Papaconstantinou, 2002. Exploitation patterns of the cuttlefish, Sepia officinalis (Sepioidea: Sepiidae), in the Mediterranean Sea. Bull. Mar.Sci., 71: 187-196. Hernández-García V., Hernández-López J.L. & J.J. Castro, 1998. The octopus (Octopus vulgaris) in the small-scale trap fishery off the Canary Islands (Central-East Atlantic). Fish. Res., 35: 183-189. Kallianiotis A. & E. Koutrakis, 1999. Structure of coastal fisheries in the Thracian Sea. Meeting of the Geotechnical Chamber of Greece - Branch of on “Fish stock management in the Thracian Sea”, May 1999, Proceedings volume: 4-12. Kallianiotis A., P. Vidoris & A. Kokkinakis, 2001. Common octopus (Octopus vulgaris, Cuvier, 1797) coastal fishery, during the peak of species reproduction. Rapp. Comm. int. Mer Medit. 36, p. 279. Kallianiotis A., Argyri A. & P. Vidoris, 2004. Catch and effort data of some target species of the artisanal fishery in the Thracian Sea- Greece. Mediterranean Marine Science (in press) Lefkaditou E. & A. Adamidou, 1997. Beach-Seine Fisheries in the Thracia Sea. Preliminary results. Proceedings of the 5th Panhellenic Symposium of Oceanography and Fisheries, , Greece, 1997- Vol. II : 21-24 (in Greek). Lefkaditou E., Sanchez P., Tsangidis A. & A. Adamidou, 1998. A preliminary investigation on how meteorological changes may affect beach-seine catches of Loligo vulgaris in the Thracian Sea (Eastern Mediterranean). In Payne A.I.L., Lipinski M.R., Clarke M.R. & M.A.C. Roeleveld (eds) Cephalopod Biodiversity, Ecology and Evolution , S. Afr. J. mar. Sci. 20 : 453-461. Lefkaditou E. and C. Papaconstantinou, 1999. Cephalopod distribution and fisheries in the Thracian Sea. Meeting of the Geotechnical Chamber of Greece - Branch of Thrace on “Fish stock management in the Thracian Sea”, May 1999, Proceedings volume: 15-32. Lefkaditou Ε., Papaconstantinou C., Tsangridis A. & P. Leondarakis, 2001. Contribution of cephalopods to the artisanal and trawl fisheries in the Thracian Sea. Proceedings of the 10th Panhellenic Ichthyological Congress on “Management and sustainable development of water resources and nearby ”, , Greece, October 2001(in Greek, Abstract in English): 45-48. Lefkaditou E., Kavadas S. & C. Papaconstantinou, 2002. Cephalopod fisheries statistics in Greek waters (NE Mediterranean). ICES Living Resources Committee, ICES CM 1999/G:4, Working Group on Cephalopod Fisheries and Life History, Lisbon, Portugal, 4-6 December 2002, 6pp. Lefkaditou E., Adamidou A., Leondarakis P., Tsangridis A. & C. Papaconstantinou, 2003. Fyke net fishery of the common octopus, Octopus vulgaris, in the Thracian Sea. Proceedings of the 11th Panhellenic Ichthyological Congress on “Advances and Development of science and technology in Fisheries- Aquaculture and Management of Water Resources”, , Greece, April 2003 (in Greek, Abstract in English): 295-298. National Statistical Service of Greece, Results of the Sea Fishery Survey by motor vessels for the years 1998 – 2002. Section C, 5 issues. Sanchez P. & R. Obarti, 1993. The biology and fishery of Octopus vulgaris caught with clay pots on the Spanish Mediterranean coast. In Recent Advances in Fisheries Biology-Contributed Paperas to 1991 CIAC International Symposium and Proceedings of the Workshop on Age, Growth and Population Strusture. Okutani T., O’ Dor R.K. & T. Kubodera (eds).Tokai University Press. pp: 477- 487. Stergiou K.I., 1988. Allocation, assessment and management of the cephalopod resources in Greek waters, 1964-1985. Rapp. Comm. int. Mer Médit. 31: 253. Tsangridis A., Sánchez, P. & Ioannidou, D., 2002. Exploitation patterns of Octopus vulgaris in two Mediterranean areas. Scientia Marina, 66:59-68. 25°30' 26°00'

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0 0 0 1234567891011 1234567891011 123456789101112 months months months Figure 2. Monthly evolution of fishing effort (vessel-days) for Octopus vulgaris and Sepia officinalis by pots and trammel-nets targeting cuttlefish (SepiaNets), shrimps (ShrimpNets) and sole (SoleNets) in the eastern Thracian Sea, during the period April 1998 - December 2003. 500 Octopus-Pots 1998 400

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Figure 3. Monthly evolution of average LPUE (kg/vessel-day) of Octopus vulgaris and Sepia officinalis from pots and trammel-nets targeting cuttlefish (SepiaNets), shrimps (ShrimpNets) and sole (SoleNets) in the eastern Thracian Sea, during the period April 1998 - December 2003.