Trawling for cephalopods off the Portuguese coast —Fleet dynamics and landings composition

1. Trawling for cephalopods off the Portuguese coast—Fleet dynamics and landings composition Fisheries Research 92 (2008) 180–188 Tereza Fonseca a, Aida Camposa,∗, Manuel Afonso-Dias b, Paulo Fonseca a, Jo˜ao Pereira a Reporter：林信宏

2. 1. Introduction finfish (Remaining marine resources) crustacean Cephalopod

3. 1. Introduction targeting cephalopods • 2002 14% • 2003 10% • 2004 13 % Cephalopod • good index ofabundance

4. Objective Management • Analyses of the landings were restricted to the fish trawling fleet operating within the depth range of distribution of these cephalopods, extending up to 200m Fishing ground Species composition related Study Distribution

5. Objective HCA GLM VMS 1. Monthly landings Year Season Vessel GT 、HP Spatial Tempora Estimation and Management

6. 2. Materials and methods • 2.1. Data sources • 2.2. Data analysis

7. Landing matrix 2.1. Data sources 1618observations (rows) • Time ：2002-2004 • Region ： Portuguese coast • Specimen ：48vessels • Number ：1618monthly • landings • fisheries ：fish trawl fisheries 31 species(columns) 15m (VMS) 65mm mesh size cod-ends 98.3% of the total landings 1618 48 X 3 X 12 = 1728 Hierarchical clustering analyses landed at least 9 months

8. squid Select of cephalopod octopus • Loligo spp. • Loligo forbesi • Loligo vulgaris • Octopodidae • Octopus vulgaris • Eledone cirrhosa • Sepia officinalis • Ommastrephidae cuttlefish

9. VMS Fleet spatial dynamics logbook GeoCrust landings data 10 min ----------- -----------   GPS Speed VMS Inspeccao-Geral das Pescas (IGP)

10. 2.2. Data analysis • Hierarchical clustering analyses • Generalized linear models • GeoCrust

11. Hierarchical clustering analyses (HCA) • landing profiles(LP) • Ward’s minimum variance • Euclidean distances HCA species (1618 X 31)

12. squid Generalized linear models (GLM) octopus season year vessel cuttlefish GT HP The statistical analyses ----- S-Plus 2000

13. 3.Results • 3.1. Landing profiles • 3.2. GLM • 3.3. Spatial patterns of fishing activity

14. octopus cuttlefish horse mackerel horse mackerel squid

15. Fig. 1. Results from HCA undertaken in a matrix of 1618 rows (monthly landings)×31 columns (species) comprising the period 2002–2004 for the 48 vessels selected from the fish trawling fleet. The number of cases in the xx axis was grouped by landing profiles (LP) defined in Table 1. The horizontal line at linkage distance 2 allowed the identification of 12 separate clusters corresponding to different LP. Four of the identified clusters correspond to LPs (3, 8, 10 and 12) associated with cephalopods.

16. octopus pouting horse mackerel

17. octopus demersal

18. cuttlefish soles octopus

19. horse mackerel pouting octopus squid

20. horse mackerel

21. 13 species

22. Regarding the landings of cephalopods LP12 ： cuttlefish (about 52%) LP3 ： squid (about 46%) LP2 ： squid (about 27%)

23. octopus landings were scattered throughout the different LPs LP2 ： octopus ( 19.8% ) LP8 ： octopus ( 18.5% )

24. Vessels related to LP4 also landed considerable amount of cephalopods octopus ： 16.3% squid ： 11.5% cuttlefish ： 6.1%

25. south：octopus (LP10 ) cuttlefish (LP12) • west：octopus (LP3) squid (LP8) other species 50 nautical miles Fig. 6. Visual display of trawling operation associated with cephalopod landings (effort distribution) from 2002 to 2004 obtained by using GeoCrust 2.0 software. (a) LP10-Octopus and (b) LP12-cuttlefish, associated with fish trawlers targeting octopus and cuttlefish off the southern coast; (c) LP3-Squid and (d) LP8-Octopus,associated with trawlers targeting octopus and squid off the west coast. Each map presents VMS data individually filtered by trawler after excluding the navigation routes. Trawling intensity (10 classes) is represented as the number of points by square (in this case 0.3 nm×0.3 nm) where the minimum corresponds to white colour and the maximum to black colour (grey scale). Maximum number of points per square (0.3 nm×0.3 nm) differs from (a) to (d).

26. 6% 16% production value

27. Fig. 2. Mean monthly landings of octopus, squid and cuttlefish associated to the selected 48 vessels of the fish trawl fleet from 2002 to 2004.

30. suggesting a seasonal alternation between octopus and cuttlefish

31. LP12 • cuttlefish： autumn winter • octopus ： spring summer LP10 Fig. 4. Cuttlefish and octopus monthly landings made by the small group of vessels permanently targeting cephalopods, from 2002 to 2004.

32. LP 3 • landing squid instead of octopus between July and December LP 8 Fig. 5. Monthly landings of squid and octopus from 2002 to 2004, made by the group of fish trawlers associated with LP3 (squid) and LP8 (octopus).

33. octopus seasonally LP 3 LP12 LP 8 LP10 LP12 LP10 LP 8 LP 3 non-cephalopod targeting LP Fig. 3. Patterns of monthly fishing activity (landing profiles’ temporal distribution) displayed by the 48 vessels (rows) selected from the fish trawling fleet from 2002 to 2004. Light grey: LP12; Dark grey, LP10; Black, LP8; Dotted, LP3; White, non-cephalopod targeting LPs.

34. 3.2. GLM

35. 3.3. Spatial patterns of fishing activity 48 fish trawlers LP3 、 LP8 、 LP10 、 LP12 Fig. 7. Visual display of trawling operations (effort distribution) by (a) the 48 selected fish trawlers and (b) excluding the trawlers associated with the four cephalopods landings profiles, from 2002 to 2004, obtained by using GeoCrust 2.0 software. Maximum number of points per square (0.3 nm×0.3 nm) differs between (a) and (b)

37. Discussion

38. Alternation species south seasonal alternation (cuttlefish、octopus) exclusively target these species abundance cycles and matches their life-cycles The landings of octopus in the Algarve increased substantially during the second quarter of the year 5.Likewise the increase in the landings of cuttlefish is also probably related to its reproductive strategy

39. patterns of vessel operation vessel south • reproductive strategy • available to the fishery after the spawning peak period • (Coelho and Martins, 1991) • These vessels are old and technologically less advanced • operating almost at all times in sheltered areas • limiting factor target species

40. Alternation species west inter-annual shifts (squid、octopus) 2. Seasonal shifts (cephalopods、fish) 3 caused by environmental change (e.g. Sobri˜no et al., 2002; Erzini,2005) 4. high levels of mortality in the life-cycle takes place at pre-recruitment life-stages (e.g. Boyle and Rodhouse, 2005; Mangold, 1983; Roberts, 2005; Worms, 1983) 5. octopus abundance is positively correlated to temperature (Lourenc¸o and Pereira, unpublished data)

41. patterns of vessel operation vessel winter (horse mackerel) west fishing strategy depending on the yearly recruitment of these species These vessels are larger trawlers and technologically more advanced spring/summer (octopus) autumn (squid)

42. fishing grounds effect on landing GT HP skipper fishing techniques advanced tracking devices lower towing speeds

43. observe the alternation from the market fishing season price amount of fish

44. Thanks for your attention