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

1. Introduction crustacean finfish (Remaining marine resources) Cephalopod

% % % 1. Introduction targeting cephalopods good index of abundance

Objective related Study Management Fishing ground Species composition Distribution 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

1. Monthly landings HCA 1.Year 2.Season 3.Vessel 4.GT 、 HP 1.Year 2.Season 3.Vessel 4.GT 、 HP GLM 1.Spatial 2.Tempora 1.Spatial 2.Tempora VMS Objective Estimation and Management Estimation and Management

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

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

Select of cephalopod Loligo spp. Loligo forbesi Loligo vulgaris Octopodidae Octopus vulgaris Eledone cirrhosa Sepia officinalis Ommastrephidae squidoctopuscuttlefish

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

2.2. Data analysis Hierarchical clustering analyses Generalized linear models GeoCrust

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

Generalized linear models (GLM) squidoctopuscuttlefish The statistical analyses S-Plus 2000 GT HP GT HP year vessel season

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

octopus cuttlefish horse mackerel squid horse mackerel

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.

octopus pouting horse mackerel

octopus demersal

cuttlefish soles octopus

squid horse mackerel pouting octopus

horse mackerel

13 species

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

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

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

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).

6% 16% productionvalue

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.

suggesting a seasonal alternation between octopus and cuttlefish

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

landing squid instead of octopus between July and December 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). LP 3 LP 8

octopus seasonally LP12 LP10 LP 3 LP 8 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 Light grey: LP12; Dark grey, LP10; Black, LP8; Dotted, LP3; White, non-cephalopod targeting LPs. LP12 LP10 LP 8 LP 3 non-cephalopod targeting LP

3.2. GLM

3.3. Spatial patterns of fishing activity 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) LP3 、 LP8 、 LP10 、 LP12 48 fish trawlers

Discussion

south 1.seasonal alternation (cuttlefish 、 octopus) 2.exclusively target these species 3.abundance cycles and matches their life-cycles 4.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 Alternation species

1.reproductive strategy 2.available to the fishery after the spawning peak period 3. (Coelho and Martins, 1991) 1.These vessels are old and technologically less advanced 2. operating almost at all times in sheltered areas 3.limiting factor target species patterns of vessel operation south vessel

west Alternation species 1.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)

west 1.fishing strategy 2. depending on the yearly recruitment of these species 1.These vessels are larger trawlers and technologically more advanced patterns of vessel operationvessel winter (horse mackerel) autumn (squid) spring/summer (octopus)

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

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