12. Annex II. Scientific Report Supporting the MPBS from Marine Sciences Institute of Barcelona (ICM) of the Spanish National Research Council (CSIC))

Home , Crystal goby

12. Annex II. Scientific report supporting the MPBS from Marine Sciences Institute of Barcelona (ICM) of the Spanish National Research Council (CSIC))

(with CORRIGENDUM I, pages. 37, 40 and 54)

Management Plan for Artisanal Fishing with Boat Seines (Sonseras) of Catalonia (Spain)

SCIENTIFIC REPORT

supporting the MPBS

(Management Plan for Boat Seine)

Scientists

Pilar Sánchez (team leader) Montserrat Demestre Jordi Lleonart Paloma Martin

Technicians

Ana Isabel Colmenero Alfredo Garcia de Vinuesa Elia Vallejo

Institute of Marine Sciences (ICM) Spanish National Research Council (CSIC)

Barcelona 2013

TABLE OF CONTENTS

1 INTRODUCTION AND OBJECTIVES...... 1 2 DATA COLLECTION...... 2 PART I: SAND EEL ...... 5 3 BIOLOGY ...... 5 3.1 Taxonomy...... 5 3.2 Length-weight relationship and length frequency...... 6 3.3 Maturity and reproduction...... 9 4 SAND EEL FISHERY...... 12 4.1 Structure of the gear and fishing techniques ...... 12 4.2 Boat seine fleet and landings...... 18 4.3 Fishing areas...... 19 4.4 By-catch composition...... 32 4.5 Assessment ...... 36 PART II: GOBIDS ...... 55 5 BIOLOGY OF GOBIDS...... 55 5.1 Taxonomy...... 55 5.2 Length-weight relationship and length frequency...... 57 5.3 Reproduction ...... 59 6 GOBIDS FISHERY...... 60 6.1 Structure of the gear and fishing techniques ...... 60 6.2 Boat seine fleet and landings...... 62 6.3 Fishing areas...... 64 6.4 By-catch composition...... 67 6.5 Assessment ...... 69 7 CONCLUSIONS ...... 73 8 REFERENCES ...... 76 1 INTRODUCTION AND OBJECTIVES

This document is meant as a scientific basis for an adequate management of the boat seine fishing gear, called “sonsera”, in the Catalan Coast.The boat seining fishery is carried out traditionally by 25 artisanal boats scattered around 6 fishing ports in the northern coast of Catalonia (NW Mediterranean). Fishing boats operate on a daily basis and landings are entirely devoted to direct human consumption, as the targeted species are highly appreciated in the region. The “sonsera” is used to catch mainly Gymnammodytes cicerelus and some very small amounts of G. semisquamatus (known both as “sonso” in Catalan) as well as some small gobids (transparent goby Aphia minuta, crystal goby Crystallogobius linearis) and occasionally very low quantities of Ferrer's goby (Pseudoaphia ferreri). Unlike the North Sea industrial sand eel fishery harvesting hundreds of thousands of tons for reduction to fishmeal, the Catalan fishery is based on small-scale boat seines yielding less than one thousand tons of catch per year. The catchs of small gobids Crystallogbius. linearis and Aphia minuta are much lower, around 4 tones per year. The scientific study is based on the historical data of the fishery over 2000- 2013, and on the data collected during the period August-2012 July-2013. Data collected during this period include i) close monitoring of catches per boat and day under a special fishing plan based on a precautionary approach (each haul is geo-referenced, and includes data on depth, time and by-catch; information provided by the fishermen though log books specially designed to this aim); and ii) a sampling campaign carried out on board boat seiners (monthly, four fishing days), to obtain data on the specific composition of the total catch, length frequency distributions of target and by- catch species, length-weight measurements, and when possible, target species sex and maturity. The scientific study has dealt with different aspects of target species biology, boat seine fishing, impact on the ecosystem and population dynamics and the results include the following topics: o Target species identification o Biological parameters: length-weight relationships, growth, maturity stages. o Size distributions by area and time o Description of the gear and the fishing operation. o Fleet composition and characteristics. o Geographical distribution of hauls and comparison with the available information on spots of marine phanerogams. o Selectivity of the fishing gear o By-catch, species identification, sizes, amounts and release of alive specimens o Stock assessment

The present document refers to the “sonsera” gear, however since this gear has two different strategies targeting sand eels and small gobies, it is organized in two parts, Part I deals with the boat seine fishery targeting sand eel; and Part II regards the boat seine fishery targeting gobid species. The study on the boat seine fishery in the Catalan Coast has been done upon request of the fishing sector and funded by them, and with agreement and close communication

1 with the Co-management committee. The study started on April 2012, with the creation of the Co-management committee. The collaboration with the fishing sector, the Administration and NGOs has been excellent and it is acknowledged.

2 DATA COLLECTION

Different sources of data were used for the scientific study 1) Official statistics. Fishing statistics from Fisheries Department of the Generalitat de Catalunya, over the period 2000-20013, until July. Data are available on a daily basis, and include the catch and income from the sale at the auction, by species and vessel, and the fishing port where the catch was landed. These data provided information on the evolution of landings and fishing effort, the unit of effort being fishing days. In the case of sand eel, information is available for the category Gymnammodytes cicerelus (which includes the 2% of the Gymnammodytes semisquamatus). As for the gobid species, information is available for Aphia minuta, Crystallogobius linearis and Pseudaphya ferreri, although the landings of this last species are very low. 2) Statistics specific of the scientific study. Daily information from fishermen logbooks. Every day they must fill in a form with the position of the hauls, depth, catch and by-catch species and time at sea. This information allowed us to know the daily catches, effort and fishing ground as well as composition of the by-catch. The fishing grounds were mapped and compared with the distribution of Posidonia beds along the Catalan Coast. 3) Characteristics of the fishing gear. At the same time gears of ten different boats were measured on the pier on five fishing ports. The dimension of the gear and the different net used on it were noted in order to establish the new regulation of the gear. 4) Sand eel sampling. Monthly sampling on board “sonsera” boats from August 2012 to July 2013 was carried out off the five ports with "sonsera" fleet (Arenys, Blanes, Sant Feliu de Guíxols, Palamós and L’Estartit). Four times a month one observer on board professional boats recorded the information on specific composition of the catches and by-catch, data on the fishing grounds where the boat seine operated and data on the description of the gear, vessel and the fishing operation. In the closed season (January and February) only one sampling per month in two ports (Arenys and Blanes) was carried out in order to obtain samples for the biological study. Samples of every haul, were collected and examined in the laboratory to identify the species, obtain length frequency distributions, individual length-weight, sex, and maturation, in order to study the life cycle of the target species (determination of at least growth parameters, duration of the reproduction period and size-at-first-maturity). All by-catch was also examined in the lab, including species identification, lengths and weights. On the laboratory specimens were measured (total length TL) to the nearest half centimetre (cm), and weighed (total weight TW) to the nearest gram (g) and with a precision of 0.01 g in gonad weight (GNW) when gonad was conspicuous.

Table 2.1. Number of different boats used in the sampling on board and crew of all these boats. Port Number of vessels Crew number L'Estartit 2 4 Palamós 2 5 Sant Feliu 3 9 Blanes 5 14 Arenys 8 22 Barcelona 2 4 Total 22 58

Table 2.2. Summary of sand eel sampling day on board with scientific observer carried out on board of sonsera boat by month and port during the scientific study. Are.= Arenys; Bla.= Blanes; S.Fe.= Sant Feliu de Guíxols; Pal.= Palamós; L’Es.= L’Estartit. Number in brackets= number of hauls. Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Are. 2(6) 2(10) 1(2) 2(8) 2(7) 1(1) 1(1) 2(5) 2(8) 2(4) 2(4) 2(5) Bla. 1(2) 1(3) 1(2) 2(7) 1(1) 1(1) 1(2) 1(1) 1(1) 1(1) 1(2) S.Fe 1(2) 1(5) 1(3) 1(3) 1(1) Pal. 1(2) 1(4) L’Es. 1(4) 1(3) 1(1) Total 4(10) 4(15) 4(13) 4(15) 3(11) 2(2) 2(2) 4(10) 4(12) 4(8) 4(6) 4(8)

2.3 Number of individuals of Gymnammodytes cicerelus and G. semisquamatus measured during the study period (August 2012-July 2013). G. cicerelus were subsampled for measurement when necessary, while all specimens of G. semisquamatus were measured. PORT G. cicerelus G. semisquamatus Arenys 16899 2660 Blanes 8746 693 S.F.+Pal+L’Es* 8519 952 TOTAL 34164 4305 *S.F.+Pal+L’Es= Sant Feliu de Guíxols +Palamós + L’Estartit

5) Gobids sampling. Monthly sampling on board “sonsera” boats from December 2012 to May 2013 was carried out off the 2 ports with sonsera fleet (Barcelona and Blanes). Twice a month one observer embarked on a commercial boat to noted the information on specific composition of the catches and by-catch, data on the fishing grounds where the boat seine operates and data for the description of the gear, vessel and the fishing operation. In close season (March to May) one embark a month in the two ports was carried out in order to obtain samples for the biological study. Samples of every haul, were collected and examined in the laboratory to identify the species, obtain length frequency distributions, individual length-weight and when possible sex, and maturation, in order to study the life cycle of the target species and

3 special distribution of the target species). All by catch was also examined in the lab, including species identification, lengths and weights. On the laboratory specimens were measured (total length TL) to the nearest half centimetre (cm), and weighed (total weight TW) to the nearest gram (g).

Table 2.4 Summary of gobids sampling with scientific observer carried out on board of sonsera boat by month and port during the scientific study. Number on bracket= number of hauls. Port Dec Jan Feb Mar Apr May Total Barcelona 1(2) 1(5) 1(1) 1(1) 1(1) 5(10) Blanes 2(7) 1(5) 1(1) 1(1) 1(1) 6(15) Total 1(2) 2(7) 2(10) 2(2) 2(2) 2(2) 11(25)

Table 2.5 Number of individuals of Aphia minuta and G. Crystallogobius linearis measured during the study period (December 2012-May 2013). PORT A. minuta C. linearis Barcelona 1408 Blanes 1434

4 PART I: SAND EEL

3 BIOLOGY

3.1 Taxonomy Gymnammodytes cicerelus Rafinesque-Schmaltz, 1810

Figure 3.1. Adult of Gymnammodytes cicerelus from the Catalan coast (from Sabates et al, 1990) Diagnosis: ventro-lateral skin-folds extending well beyond pectoral fins to anus. Dorsal rays 56-59; anal rays 27-31; pectoral fin ray 12-15. Lateral line branched. Vertebrae 66- 67 (mode 66). Colour: iridescent silver, while the back is bluish-grey and the flanks and belly whitish. In this species it is possible to observe a strip of quit marked dark pigmentation along the top part of the flanks and over the head (Sabates et al, 1990. Size: to 17 cm SL. Habitat: inshore to 15 m depth. Food: probably plankton. Reproduction: winter spawner. Distribution: Mediterranean and Black Sea, overlapping with G. semisquamatus in the western Mediterranean. Larvae: Sabates et al (2003) working on the North of the study area found larvae of G. cicerelus in winter (January-March).

Gymnammodytes semisquamatus Jourdain, 1879

Figure 3.2. Adult of Gymnammodytes semisquamatus from the Catalan coast (from Sabates et al, 1990) Diagnosis: ventro-lateral skin folds extend from the base of the pectoral fin to just beyond the rear end of the fin. Dorsal rays 53-59; anal rays 26-32; pectoral fin ray 12- 15. Lateral line branched. Vertebrae 64-72. Colour: Body silver, while the back is dark brown and the flanks and belly whitish. The strip of pigmentation on the flanks is brownish and barely appreciable, though it does exist (Sabates et al, 1990). Size: to 28 cm SL (Atlantic). Habitat: typically offshore over shell-gravel, also inshore where shell-gravel beaches occur. Food: plankton. Reproduction: summer batch spawner, ripe fish occurring from March to September in North Atlantic, but probably with more restricted spawning periods for each population (Reay, 1986) and winter/spring spawner in the Mediterranean (present study).

5 Distribution: eastern North Atlantic from the southern coast of Norway and the Shetlands (61° N) to Spain (36° N) including all coasts of the British Isles and the North Sea, but not the Baltic, and extending along northern Mediterranean coasts to at least 3° E (Reay, 1986; Sabates et al 1990; Sabates et al, 2003). Larvae: Sabates et al (2003) working on the North of the study area found larvae of G. semisquamatus in winter (January-March) and few specimens in a 24-h sampling cycle carried out in July.

3.2 Length-weight relationship and length frequency Gymnammodytes cicerelus Length-weight relationship

Figure 3.2.1. gives the length-weight relationship for G. cicerelus and G. semisquamatus whole population. Positive allometric growth was observed in species.

10 G. cicerelus 8 G. semisquamatus 9 y = 0,001937x3,139 7 8 y = 0,002277x3,017 R² = 0,971 6 7 R² = 0,961 (gr)

(gr) 6 5 5 4 weight

weight

4 3 3 Total 2 Total 2 1 1 0 0 2 7 12 17 2 7 12 17 Total length (cm) Total length(cm)

Figure 3.2. 1. G. cicerelus and G. .semisquamatus length-weight relationship (a and b parameters) obtained for the whole study period.

Length frequency The monthly length-frequency distribution in the catches of G. cicerelus ranged between 3.5 and 14.5 cm, with mean size increasing throughout the fishing season from February (when the first shoals appeared) until January next year (Fig. 3.2.2.).

6 August February'13 0,3 cy n=4991 0,4 n cy n=702 e n u0,2 e0,3 q u e q fr e0,2 0,1 fr ve ti ve0,1 la ti e 0 la R e 0 3 5 7 9 11 13 15 R 3 4,5 6 7,5 9 10,5 12 13,5 15 TL (cm) TL (cm)

September March'13 0,2 n=5585 0,6 n=4164 cy cy n n e0,15 e u u0,4 q q re 0,1 e f fr e 0,2 v0,05 ve ti ti la la e 0 e 0 R R 3 5 7 9 11 13 15 3 5 7 9 11 13 15 TL (cm) TL (cm)

October April'13 0,2 0,4 n=3413 cy n=4362 cy n n e0,15 e0,3 u u q q re 0,1 e0,2 f fr e v0,05 ve0,1 ti ti la la e 0 e 0 R R 3 5 7 9 11 13 15 3 5 7 9 11 13 15 TL (cm) TL (cm)

November May'13 0,2 0,3 n=2284 cy n=2904 cy n n e0,15 e u u0,2 q q e 0,1 re fr f e0,1 ve0,05 v ti ti la la e 0 e 0 R R 3 5 7 9 11 13 15 3 5 7 9 11 13 15 TL (cm) TL (cm)

December Juny'13 0,3 n=1796 0,3 y cy c n n=1619 n e e0,2 u0,2 u q q e re r f f e0,1 e0,1 v iv ti t la la e 0 e 0 R R 3 5 7 9 11 13 15 3 5 7 9 11 13 15 TL (cm) TL (cm)

January'13 July'13 0,3 n=487 0,3 cy cy n n n=1857 e e u0,2 u0,2 q q e re fr f 0,1 e0,1 ve v ti ti la la e 0 e 0 R R 3 5 7 9 11 13 15 3 5 7 9 11 13 15 TL (cm) TL (cm) Figure 3.2.2. Monthly length-frequency distribution (August 2012 to July 2013) of G . .cicerelus (n = number of individuals sampled).

Gymnammodytes semisquamatus

Length-weight relationship The monthly length-frequency distribution in the catches of G. semisquamatuss ranged between 4.5 and 14 cm, with mean size increasing throughout the fishing season from March (when the first shoals appeared) until February next year (Fig. 3.2.3.).

August February'13 0,3 0,4 cy n=1370 cy n n n=389 e e0,3 u0,2 u q q e re0,2 fr f 0,1 e ve v0,1 ti ti la la e 0 e 0 R R 34,567,5910,51213,515 34,567,5910,51213,515 TL (m) TL (m) September March'13 0,6 0,6 y n=122 cy c n n=157 n e e u0,4 u0,4 q q e re fr f 0,2 e0,2 ve iv ti t la la e 0 e 0 R R 34,567,5910,51213,515 34,567,5910,51213,515 TL (m) TL (m) October April'13 0,6 0,3 y cy c n=164 n n=511 n e e u0,2 u0,4 q q e re fr f 0,1 e0,2 ve iv ti t la la e 0 e 0 R R 34,567,5910,51213,515 34,567,5910,51213,515 TL (m) TL (m) November May'13 0,4 0,2 y n=181 cy n=550 c n n e0,15 e0,3 u u q q e 0,1 re0,2 fr f e ve0,05 iv 0,1 ti t la la e 0 e 0 R R 34,567,5910,51213,515 34,567,5910,51213,515 TL (m) TL (m) December Juny'13 0,3 0,4 n=6 y cy c n=525 n n e0,3 e0,2 u u q q e0,2 re r f f e0,1 e v iv 0,1 ti t la la e 0 e 0 R R 34,567,5910,51213,515 34,567,5910,51213,515 TL (m) TL (m) January'13 July'13 0,4 0,6 cy cy n=6 n n e0,3 n=324 e u u0,4 q q e0,2 re fr f e0,2 ve0,1 v ti ti la la e 0 e 0 R R 34,567,5910,51213,515 34,567,5910,51213,515 TL (m) TL (m) Figure 3.2.3. Monthly length-frequency distribution (August 2012 to July 2013) of G. .semisquamatus (n = number of individuals sampled).

8 For further information on the length distributions see section 4.5 "Data from the scientific study".

3.3 Maturity and reproduction Of the total specimens, 1935 gonads were removed (1278 G. cicerelus; 657 G. semisquamatus), the sex determined, and macroscopically assigned to a gonadal stage based on the six maturity phases scale (I= Immature; II= Resting; III= Developing IV= Advanced Maturation; V= Spawning; VI= Post spawning). Sex was easily assessed macroscopically in mature individuals. However, gonads from small individuals were indistinguishable macroscopically because ovaries and testes were small and translucent. Fish that were too small to determine their sex or assign a gonadal phase to were classified as indeterminate. The spawning season was established from the analysis of the monthly variation of the maturity phases and the changes in gonadosomatic (GSI) index for each sex, which was calculated as: GSI = (GNW / TW) × 100 Where TW is total weight and GNW gonad weight

Gymnammodytes cicerelus Spawning season and size at first maturity Monthly distribution of macroscopic classification of the maturity phases (Fig. 3.3.1.) revealed the maximum occurrence of advanced maturation females (phase IV) from November to February. The presence of spawning females (phase V) was observed from November to February, with a maximum peak in January. Females in immature and resting phases (I, and II,) were found from March to October. Males showed the same pattern as females, with a maximum peak of individuals in phase V in December- January. Gonadosomatic index (GSI) was calculated for mature males and females. The mean GSI for females was highest from November to March, with a peak of maximum activity in December (4.31) and January (8.41) (Fig. 3.3.2). Males showed the same pattern as females with a peak of maximum activity in January (13.55)

n = 826 n = 452 Maturity Stage G. cicerelus (Females) Maturity Stage G. cicerelus (Males)

100% 100% 90% 90% 80% 80% VI VI 70% 70% V V 60% 60% IV IV 50% 50% III III 40% 40% II II

30% (%) Frequency

Frequency (%) Frequency 30% I I 20% 20% 10% 10% 0% 0% July May July May April April June June March March August August January January October October February February November December November December September September Month Month

Figure 3.3.1. Monthly distribution of males and females maturity phases of gonads based on macroscopic examination.

9 G. cicerelus (Females) G. cicerelus (Males)

9 n = 772 16 n = 427 8 14 7 12 6 10 5 8 4 6 Mean GSI Mean Mean GSI Mean 3 2 4 1 2 0 0

Month Month

Figure 3.3.2.. Monthly changes in the mean gonadosomatic index for females and males of G. cicerelus. The size at-first-maturity (size at which 50% of individuals are mature) was 7.32 cm TL (fig 3.3.3). This value has been obtained fitting a normal cumulative curve to the maturity tax per length.

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0 468101214

Figure 3.3.3. Maturity ogive for females of G. cicerelus.

A B

C D

Figure 3.3.4. Females of G. cicerelus showing different maturity phases. A= phase III; B= phase IV; C= phase V; D=detail of phase V.

A B

Figure 3.3.5. Males of G. cicerelus showing different maturity phases. A= phase V; B= detail of phase V.

11 Gymnammodytes semisquamatus Spawning season and size at first maturity Monthly distribution of macroscopic classification of the maturity phases (Fig. 3.3.4.) revealed the maximum occurrence of advanced maturation females (phase IV) from December to March. The presence of spawning females (phase V) was observed from December to March, with a maximum peak in February. Females in immature and resting phases (I, and II,) were found from March to December. Males showed the same patter than females, with a maximum peak of individuals in phase V in January- February. The smallest mature female and male were 7.2 cm and 7.6 cm total length respectively.

Maturity Stage G. semisquamatus (Females) n = 385 Maturity Stage G. semisquamatus (Males) n = 272

100% 100% 90% 90% 80% 80% VI VI 70% 70% V V 60% 60% IV IV 50% 50% III III 40% 40% II 30% II

Frequency (%) Frequency 30% I (%) Frequency 20% 20% I 10% 10% 0% 0% July May July April May April June June March March August August January October January October February February November December November December September September Month Month

Figure 3.3.6. Monthly distribution of males and females maturity phases of gonads based on macroscopic examination. Gonadosomatic index (GSI) was calculated for mature males and females. The mean GSI for females was highest from December to February, with a peak of maximum activity in January (8.47) and February (6.3) (Fig. 3.3.5). Male showed the same pattern as females with a peak of maximum activity in January (11.27)

G. semisquamatus (Females) G. semisquamatus (Males)

n = 254 9 n = 335 12 8 10 7 6 8 5 6 4 Mean GSI 3 GSI Mean 4 2 2 1 0 0

Month Month

Figure 3.3.6. Monthly changes in the mean gonadosomatic index for females and males of G. semisquamatus.

4 SAND EEL FISHERY

4.1 Structure of the gear and fishing techniques The “sonsera” is a fishing gear that belongs to the group of boat seine; here it is not a trawl gear. Sand eel (Gymnammodites cicerelus y G. semisquamatus), that in Catalonia

12 are known as “sonso”, and the little goby generically known as “llengüeta”, transparent goby (Aphya minuta) and crystal goby (Cristalogobius linearis), can only be fished with the “sonsera”. This gear is not used for targeting any other species. The monthly observations on board 25 authorized fishing boats during the scientific study between August 2012 and July 2013 allowed to determine the distribution of the fishing grounds of sand eel, transparent goby and crystal goby visited by this fleet. Sand eel presents a very restricted distribution, being found only in swallow sandy bottoms coastal habitats in the Catalan coast, between Barcelona and L’Estartit ports. It is normally fished between 6 and 16 m, not being permitted below 30m. In its northernmost distribution, from Blanes to L’Estartit, the sandy bottoms are located in a rocky coast, where depths of 10-15m are located in less than 400m from the coast. In the southern area, between Barcelona and Blanes, the coastline is very different; the continental platform here is smooth and wide and generally only a 7m average depth is found within 600m from the coast (Figure 4.1.1) This sand eel essential habitat located very close to the coast is the reason why this fishing activity must be carried out in swallow coastal grounds. Therefore, the sand eel fishery is regulated in order to be exclusively carried out in sandy bottoms and it is totally forbidden to fish on beds of phanerogams or in rocky bottoms.

Figure 4.1.1. Fishing areas of “sonsera” in the northern fishing grounds (above) and southern fishing grounds (below) On the other hand, the two goby are mainly found in muddy or sandy-muddy habitats. Aphya minuta is fished between 7 and 12m in the southern fishing grounds, basically near Barcelona’s port coast, whereas Cristalogobius linearis is mainly distributed in northern fishing grounds and presents a deeper bathymetric range, being normally fished between 30-50m depth. In this case it is also forbidden to fish on beds of phanerogams or in rocky bottoms.

13 Structure of the fishing gear The “sonsera” is a net gear and the structure is based on two long lateral wings and a bag between of the wings including the codend. The dimensions of these structures are as follows:  Maximum length of wings: 125 m.  Maximum height of wings: 35 m.  Maximum length of codend: 30 m. A rope no longer than 100m attached at the end of each wing The draw in Figure 4.1.2 shows the structure of the boat seine “sonsera”.

Figure 4.1.2. Drawing of the boat seine “sonsera” characteristics

The mesh size decreases from the end of the wing (100 mm; 4 Ppp) to the net mouth (16 mm; 24 Ppp). The mesh size of the codend decreases from the mouth (33 mm; 12 Ppp), toits lower white portion of the mesh of the codend (no less than 2mm; 200 Ppp). A cylindrical net extension is found at one end of the codend and sometimes another extension can be found at the other end. The catch is removed from these extensions. The above sizes are the minimum ones for the ends of each gear section. However, the wings and the codend constructive characteristics as well as the mesh size configuration may vary according to the habits and customs of each fishermen and net builders. The wings have a leadline with large number of weights along the net bottom (a maximum of 6 weights per m; maximum 250g each weight), and a floatline along the top of the net to provide flotation in order to achieve a positive buoyancy during the dropping operation (Figures 4.1.2 and 4.1.3).

Figure 4.1.3. Several images of “sonsera”: i) entire gear from wings to codend; ii)wings; iii) end of wings where rope is attached; iv) different mesh size of the wing; v), vi) mouth; vii) leadline and floatline. These fishing gear characteristics belong to the sand eel as well as the “llengüeta” fisheries. However, certain variability in the dimension of the “sonsera” previously described is permitted due to the geographic and bathymetric features of the northern sand eel’s distribution area. In this area, between Blanes and L’Estartit, the usual fishing grounds are located between 13 and 16 m, no deeper than 30m. Therefore, a maximum wing height of 60m and a maximum rope length of 200m are allowed. Regarding the crystal goby (Crystalogobius linearis) fisheries in the northern fishing grounds, a length of 200m of the rope is also allowed. Fishing techniques By the observations on board carried out during the scientific study in all the ports where there is “sonsera” fishing activity, the fishing technique it has been described, and at the same time, the impact on the marine environment of this fishery operation has been estimated.

15 The fishing process begins with the target species detection and identification by the echo-sounder. The identification allows both, to assess the target school size and to detect the by-catch species presence. This is the operation step that assures the gear’s selectivity, as fishermen are able to control the possible by-catch species presence and to evaluate the high selectivity outcome of the haul (Figure.4.1.4, i) In the second step the net is dropped into the sea and will surround externally the school of fish by dropping at a steady pace the rope, the wing, the codend, the second wing and the second rope. It is very important to keep an eye on the sea currents in order not to fail the operation of encircling the school of fish. A buoy indicating the position of school of fish is kept during the surrounding operation which helps to finish the net dropping correctly. This buoy is dropped when the identification of the target school is done. When the entire gear is dropped and the two ropes retrieved on board, the net is left so it can drop until it almost brushes the seabed. After that, pulling and recovering the two ropes, the net is correctly placed lying over the bottom in a way that prevents the escape of the fish. Special attention must be put in this operation, as if too much traction power is applied, the gear could be lift from the bottom and it would close in an uncontrolled way, which would lead to the operation fail, and, consequently, to the fishing fail. A mechanical winch is used to recover the net on board and allows slowly and in a continuous way pull back all the different sections of the art, both sides at the same time ropes and wings up to the codend. The boat does not move but the engine is used to stabilize the boat in order to maintain it in a fixed position and not to move the gear away from the school of fish (Figure 4.1.4, ii to vi). Finally, the codend is recovered manually when the boat is positioned sideways, and its content is removed by the cylindrical extension and on board placed in different containers (Figure 4.1.4, vii to ix).

Figure 4.1.4. Different sequences of the fishing operation.

17 All this fishing operation is normally carried out by the stern, although some boats make it from the side of the boat. Afterwards, the anchor is dropped to the sea by the prow of the boat in order to maintain the boat in a stable position (Figure 4.1.4, x to xi). During this last process, the by-catch species are separated from the target species and are returned to the sea alive by extracting them from the containers where the catch is being placed. Sometimes, less frequently although more effective, fishermen use sieves in which by-catch species are retained. Then the by-catch species are returned easily to the sea (Figure 4.1.4, xii to xv

4.2 Boat seine fleet and landings Boat seine fleet At present the boat seine fleet consists of 26 vessels, which work with two or three fishermen on board. Annex I shows the census of the vessels authorized to use the boat seine locally called "sonsera" (see description in section 4.1). The overall characteristics of the boat seiners are: length between perpendicular (m) = 8.05±1.75 and power (kw)= 42.55±20.60. Landings Data on sand eel landings and activity of the boat seine fleet were obtained from the daily slips from the sale at the auction that takes place upon the arrival of the vessels at port (data source: fishing statistics elaborated by the Fisheries Department of the Generalitat de Catalunya). Data were available on sand eel daily landings (the two species combined), by vessel, for the period 2000- 2013 (until July; 25456 records). Considering the dominance of G. cicerelus in the landings (98% in weight), the data are assumed to correspond to the Mediterrranean sand eel.

900 Escala 800 Annual landings

700 Barcelona 600 500 Sant Feliu 400 tonnes Roses 300 200 Palamos 100

0 Arenys 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 Blanes 2013(Jul) Fig. 4.2.1. Mediterranean sand eel landings in the Catalan Coast over 2000-2013 (July), by fishing port.

The boat seine fleet operates in the central and northern Catalan Coast (i.e. from Barcelona to the north). Over the studied period, the annual landings fluctuated between around 100 annual t in 2001 and 2006, and a minimum of 42 t in 2007, and a maximum of 819 t in 2012. The fishing ports with highest landings were Blanes, Arenys de Mar and Palamós. In 2012 and 2013 landings in Sant Feliu de Guíxols markedly increased. It seems that at least until 2010 landings were under- reported. In fact, highest annual landings corresponded to 2010- 2012 (Fig. 4.2.1).

18 Fishing days, per fishing season The fishing season starts on March, 1st, and finishes on December, 15th. The unit of effort considered in this study is the number of fishing days (i.e. the sum of the number of days each boat seiner sold sand eel at the auction upon arrival to port). Landings and fishing days displayed the same trend until 2012 and 2013 (Fig. 4.2.2). Furthermore, the CPUE (kg/day per vessel) for the whole fishing season increased in 2013, despite the decreasing landings (Fig.4.2.3). Both the trend change, that is, higher landings produced in less fishing days in 2012, along with increasing CPUE in 2013 result from the in- season management regulations agreed by the Co-management Committee of the Catalan sand-eel Fishery and implemented during the scientific study.

3500 900 800 3000 Fishing days Landings 700 2500 600 (t) 2000 days 500

1500 400 landings fishing 300 1000 200 500 100 0 0 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012

2013(Jul) Fig. 4.2.2. Fishing days and sand eel landings trend in the Catalan Coast over 2000-2013 (July).

900 Landings (t) 800 Annual CPUE (kg/day per vessel) 700 600 500 400 300 200 100 0 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012

2013(Jul) Fig. 4.2.3. Landings and annual CPUE (kg/day per vessel) trend in the Catalan Coast over 2000-2013 (July). Further information and analysis of landings and CPUE is presented in section 4.5.

4.3 Fishing areas Fishing activity has been monitored through log books, from June 2012 to June 2013. Information is available, on a daily basis and by vessel and fishing operation, on the target species catches, coordinates and depth of the fishing ground, time at sea, and by- catch species (Annex IV). The analysis of these data allowed evaluating the fishing effort, in terms of fishing days, number of hauls, hours at sea, and fishing ground. Data are available on a total of 1906 daily trips and 3038 hauls, carried out by the boat seine "sonsera" fleet with base in the fishing ports of Arenys de Mar, Blanes, Sant

19 Feliu de Guixols, Palamos, L’Estartit in 10.5 months (from 16 December to 1 March fishing ban was applied). Fishing hours at sea showed an increasing trend from June 2012 (2.47 hours) to September. From September onwards, until the end of the fishing season in December, the time spent at sea was >4 hours. When season started in March 2013, the hours at the sea were 3.47, decreasing until June 2013 to 2.4, the same value as in the previous season (fig. 4.3.1).

6 Hours on the sea 5

3 Hours

Arenys Blanes Sant Feliu Palamos L'Estartit Total

Figure 4.3.1 Average of daily hours spend on the sea by month and fishing port.

Some differences between ports could be observed. In general fishermen worked in the area nearby the base port of the fishing boat and moved further seeking for the target species as the season advanced. The maps were generated using the Google Maps facility. The data were, in a first step stored in an excel file and from it, through the format “csv” (comma-separated values), converted in kml format (Keyhole Markup Language) directly readable by Google Maps using the software “scv2kml v1.0.2” created by ebd (http://www.ebdearth.com/). In such a process a series of layers were created in Google Maps:  Individual hauls, represented as a georeferenced point with the complete available information per haul. In the figure 4.3.2 an example of the haul metadata pop up is presented. The data included are:

- Boat name - Hour of starting the haul - Port - Depth (in m if not indicated other unit – fathoms) - Day Percentage of Gymnammodytes semisquamatus - Month - Percentage of Gymnammodytes cicerelus - Year - Total weight of Gymnammodytes spp. - Haul - Quantitative evaluation of size (P small, M - Hour leaving the port medium, G large) - Hour arriving to the port - Discarded Gymnammodytes spp. - Place of auction

Figure 4.3.2 Unfold pop up of a haul

 Scientific hauls. The same contents  Isobaths of 5, 10, 20, 30, 50, 100 and 200 m  Spots of marine phanerogams

The maps show the position of the hauls during the studied period. Even when the fishing took place in the area corresponding to base port of the fishing boats, the fleet of Arenys overlapped their fishing ground with the Blanes fleet on fishing grounds between the two ports. Boats from Sant Feliu de Guixols, Palamos and L’Estartit are those that displayed highest mobility. The depths where the fishing operations took place ranged from 4 m to 15 m for the fleet of Arenys and Blanes, and from 5.5 m to 30 m for the boats of Sant Feliu de Guixols, Palamos and L’Estartit. As shown by the maps, the "sonsera" is not used on sea bottoms characterized by the presence of sea grass meadows, in particular Posidonia oceanica. The fishing activity can have been carried out close to, but not directly on Posidonia meadows

Figure 4.3.3 General map showing the position of sand eel fishing grounds. Round dots= fishing position from fishermen log book.Square dots = position of hauls with observer on board. Dark green spots Posidonia according 1992 survey; light green spot Posidonia according 2012 survey (only present in front of Mataro)

23 24

26 27

Figure 4.3.4. Detail of the different fishing grounds along de coast from south (Arenys) to north (L’Estartit).

31 4.4 By-catch composition The analysis of the boat seine catch developed during the scientific study has evidenced the high selectivity of the “sonsera”, as the presence of by-catch species can be detected by the echo-sounder, which allows performing selective fishing operations resulting in catches without or with very few non- target species. The percentage in weight of by-catch species regarding the total sand eel’s catch was very low over the study period, around 2-3%. During the scientific study the commercialization of the by-catch species was prohibited The by-catch composition from the fishing grounds where the "sonsera" boat seine fleet operated was analysed through scientific cruises from August 2012 to June 2013. Samples were obtained on board four times a month from five ports in the Catalan coast (Arenys de Mar, Blanes, Sant Feliu de Guixols, Palmós and L’Estartit). Even during the closed season, from 15 December to 28 February, samples of non-target species were collected to complete the information on their presence along an annual cycle. Later, in the laboratory, species were identified and length and weight were obtained for each specimen. In a parallel way, fishermen filled in log books with the daily information of catch including sand eel and by-catch species, depth, geographic position and time at sea of each haul. In order to assess the “sonsera” selectivity two different information sources were analyzed: on board observers, and fishermen log-books. Two scenarios were evaluated from the information of the on board observers. In the first one, all by-catch species retained in the gear and not thrown back alive into the seawere considered. The results reported percentage less of 2 % (1.57%) regarding the total catch of non-target species (Table 4.4 1).

Table 4.4.1. Monthly catch and percentage of main by-catch species regarding the total sand eel landings from the on- board observers information

Kg by-catch % retained retained August September October November December Total vs sand ell T. draco 0 2.87 2.38 0.07 0.15 5.47 0.06 S. japonicus 0.1 2.7 0.15 0 0 2.95 0.03 S. saurus 1 1.8 2.6 15.4 0 20.8 0.22 Mullus spp 0 0 0.2 0 0 0.2 0.00 S. aurata 0000000.00 P. erythrinus 0.5 5.25 5.964 13.2 8.436 33.35 0.35 C. linguatula 0000000.00 X. novacula 2.1 1.68 2.52 21.35 0 27.65 0.29 Rajidae 6 2 0 0.755 0 8.755 0.09 S. dumerili 0 1.5 0.3 0.9 0 2.7 0.03 Trachurus spp. 0000000.00 B. podas 3.45 1.9 3.35 15.45 0.1 24.25 0.25 Spicara spp. 0 0 0 22 0.15 22.15 0.23 Cephalopods 1 0 0.95 0.73 0.24 2.92 0.03 Total 14.05 19.77 18.414 89.855 9.076 151.165 1.57 kg Sand ell 2210 2250 2135 1700 1315 9610 % by‐catch 0.64 0.88 0.86 5.29 0.69 1.57 In the second scenario, two different cases were considered: i) the by-catch species percentage which were retained but released alive at sea, and ii) the retained by-catch species not released which arrived dead at port. The percentages were 0.31 % and 0.19% respectively (Table 4.4.2a, b).

Table 4.4.2a. Monthly catch of the main by-catch species, and percentage of alive regarding the total sand eel landing from the on board observers information

Kg by-catch % alived retained March April May June July Total vs sand ell T. draco 0 0.49 0.56 0.35 2.1 3.5 0.03 S. japonicus 6.8 6.45 0 0 0 13.25 0.11 S. saurus 0 0 1 0 1.7 2.7 0.02 Mullus spp 0000000.00 S. aurata 0000000.00 P. erythrinus 2.25 3.15 0.85 1.2 0.9 8.35 0.07 C. linguatula 0000000.00 X. novacula 0 0 0.14 0.07 0.35 0.56 0.00 Rajidae 0000000.00 S. dumerili 0000000.00 Trachurus spp. 5.15 3 0.2 0.6 0.15 9.1 0.07 B. podas 0 0.5 0.25 0.45 0.2 1.4 0.01 Spicara spp. 0000000.00 Cephalopods 0000000.00 Total 14.2 13.59 3.07 2.67 5.4 38.93 0.31 kg Sand ell 3755 2415 2370 2160 1840 12540 % by‐catch 0.38 0.56 0.13 0.12 0.29 0.31

Table 4.4.2b. Monthly catch of the main by-catch species, and percentage of dead regarding the total sand eel landing from the on board observers information

Kg by-catch % dead retained March April May June July Total vs sand ell T. draco 0 1.68 0.56 0 0.28 2.52 0.02 S. japonicus 0.75 0.3 0 0 0 1.05 0.01 S. saurus 1.2 4.3 1 0 1.5 8 0.06 Mullus spp 0000000.00 S. aurata 0.2 0.4 0 0 0 0.6 0.00 P. erythrinus 2.4 1.2 0.85 0.3 0 4.75 0.04 C. linguatula 0000000.00 X. novacula 0 1.05 0.14 0.21 0.42 1.82 0.01 Rajidae 0000000.00 S. dumerili 0000000.00 Trachurus spp. 1.05 0.3 0.2 0 0 1.55 0.01 B. podas 0.05 1.5 0.25 0.2 0.25 2.25 0.02 Spicara spp. 0.4 0.05 0 0 0 0.45 0.00 Cephalopods 0.75 0.23 0 0 0 0.98 0.008 Total 6.8 11.08 3.07 0.71 2.45 24.11 0.19 kg Sand ell 3755 2415 2370 2160 1840 12540 % by‐catch 0.18 0.46 0.13 0.03 0.13 0.19

Fishermen information from log-books accounts for retained by-catch species and released alive to sea. In this case, the weight percentage was also very low, varying depending on the species and month but ever <0.5% (Table 4.4.3).

33 Table 4.4.3. Monthly catch of the main by-catch species, and percentage of returned alive at sea regarding the total sand ell landing from the fishermen log-book information

Month/kg Sand ell T. draco S. japonicus S. saurus Mullus spp S. aurata P. erythrinus C. linguatula X. novacula Rajidae S. dumerili Trachurus spp. B. podas Spicara spp. Cephalopods T otal kg monthly % august 99299.40 13.25 15.80 0.82 0.00 1.00 35.10 0.00 7.10 0.00 20.00 0.00 14.67 0.00 0.00 107.74 0.11 september 70933.50 6.10 0.00 0.30 0.00 1.50 7.83 1.70 11.25 7.00 0.01 8.44 44.16 0.05 88.33 0.12 october 65813.00 6.25 0.00 1.75 0.00 1.00 15.23 1.28 47.12 1.50 9.00 1.00 10.83 0.00 0.30 95.25 0.14 november 76057.90 1.03 0.00 0.25 0.00 0.00 83.18 1.20 46.23 0.00 45.80 0.00 15.05 0.00 0.50 193.24 0.25 december 27561.30 2.05 0.00 0.00 0.00 0.00 7.10 1.00 0.75 1.00 0.00 0.20 0.45 15.05 2.50 30.10 0.11 march 82159.07 5.19 108.50 7.85 1.00 1.20 42.70 0.00 0.57 0.00 0.25 43.15 5.58 92.60 8.50 317.09 0.39 april 108853.40 38.19 316.85 9.60 2.95 47.40 0.00 1.50 3.30 2.80 40.05 6.55 12.25 13.35 494.79 0.45 may 79774.65 63.49 73.15 24.20 2.40 0.50 68.65 0.00 5.20 2.00 0.00 25.43 2.16 0.00 5.20 272.37 0.34 june 128223.20 69.12 28.22 25.55 0.50 1.10 89.52 0.10 13.88 3.50 0.00 38.35 12.05 290.29 8.10 580.28 0.45 july 104246.35 15.95 39.30 22.40 0.00 0.70 48.07 0.10 13.55 1.10 0.00 70.70 14.42 229.10 2.80 458.19 0.44

Total kg 842921.77 220.61 581.82 92.72 6.85 7.00 444.78 5.38 147.14 12.40 84.85 218.89 90.20 683.45 41.30 2637.37 0.313 % by‐catch 0.03 0.07 0.01 0.001 0.001 0.053 0.001 0.02 0.001 0.01 0.03 0.01 0.08 0.005 0.313 vs sand ell Considering all the three tables information, the species with higher percentage were common pandora (0.35%), cleaver wrasse (0.29) and wide-eyed flounder (0.25%). The percentages of by-catch species changed depending on the species and the month but it is important to notice that the control achieved at commercialization level of the non-target species evidenced a good management performance. Minimum size Taking into account all by-catch species which appeared in the catches, 16 species were most frequent and abundant during the study period. Common pandora Pagellus erythrinus, cleaver wrasse Xyrichtys novacula, wide-eyed flounder Bothus podas, the greater weever Trachinus draco and the lizardfish Synodus saurus were present in practically all analyzed catches. Of these 5 species, according to Council Regulation (EC) 1967/2006 only the common pandora has a regulated minimum landing size (12cm total length, TL). The percentage in weight of common pandora in sand eel’s catches during the year, was highest in November (0.11%), May (0.12) and June (0.15%).

34 Table 4.4.4. Monthly by-catch and % vs sand eel catch of common pandora.

Month kg by‐catch (%) Aug 35.1 (0.04%) Sep 7.83 (0.01%) Oct 15.225 (0.02%) Nov 83.18 (0.11%) Dec 7.1 (0.03%) Mar 42.7 (0.05%) Apr 47.4 (0.05%) May 68.65 (0.12%) Jun 89.52 (0.15%) Jul 48.07 (0.05%) In these three months catches focused in individuals of > 12cm. Over the rest of the months, common pandora catches varied between 0.01% and 0.05%. In October, common pandora indivudals of <12cm appeared, but its percentage was 0.02% of the total catch (Fig.4.4.1a)

Pagellus erythrinus

90 Sep 80 Oct 70 Nov 60 Dec

50 Mar individuals Apr

of 40

Nomber 10

0 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 TL cm

Figure 4.4.1a. Length frequency distribution of by-catch of Pagellus erytrhinus Among all the other by-catch species, two of them present a regulated minimum landing size, horse- mackerel Trachurus spp., which has a 15 cm TL minimum size and the chub mackerel Scomber japonicus, with 18cm TL minimum size. Over all the study period, the global weight percentage of horse-mackerel in the total catch was 0.02%. Almost all caught individuals (>23cm TL) clearly exceeded the minimum catch size and only 11 individuals in September were under 15 cm.

Trachurus spp 30

15 individuals Sep

of 10 Dec

5 Mar

0 Number 357911131517192123252729313335 TL cm

Figure 4.4.1b. Length frequency distribution of by-catch of Trachurus spp

35 Cephalopods were represented by three species Loligo vulgaris, Octopus vulgaris and Sepiaofficinalis and did not present important percentages into the by-catch any of them. During the study period only 4 individuals of red mullet Mullus barbatus were caught in October (2 of 6 cm and 2 of 7 cm) (table 4.4.1). The information of table 4.4.3 from log-books did not has size of individuals In conclusion, taking into consideration the control measures to avoid the commercialization of by-catch species and the good results regarding the gear selectivity and the release alive into the sea of the by-catch species (see videos 11, 22 and 33), it is recommended to limit the by-catch species presence to a maximum weight percentage of 1% of the total catch or less than 5kg of total weight. Furthermore, by- catch species commercialization must remain forbidden.

4.5 Assessment Species Only one species of sand eel, Gymnammodytes cicerelus, has been assessed. This is due mainly to the very different role of both species in the fishery. G. cicerelus account for 98% of total catch in weight, while G. semisquamatus represents only 2%. This is a short lived species, almost annual, 94% of the caught individuals belong to the first annual class (aged 0 to 1), only 6% are more than one year old. There are not parameters and assessments for those species in the bibliography, however the lesser sandeel Ammodytes marinus, has been analysed and assessed in the North Sea, these parameters are hardly applicable to G. cicerelus as it will be shown later. Data Historical Series The data source on landings and fishing effort (fishing days) is the same used in section 4.2. Data are presented at annual and monthly scales. The unit of effort considered is the number of fishing days (i.e. the sum of the number of days each boat seiner sold sand eel at the auction upon arrival to port). Monthly catch per unit of effort (CPUE) was calculated as i) kg per day and vessel; and ii) numbers per day and vessel. From the sampling on board (August 2012 to July 2013) it was possible to know the monthly mean size trend of the Mediterranean sand eel, as well as the parameters a and b of the length weight relationship, which allowed the estimation of a monthly mean weight. These monthly mean weights were applied to the whole data series, so as to express the monthly landings as numbers of individuals caught. Catch and CPUE Over 2000- 2013 (July), sand eel landings displayed marked fluctuations (Fig. 4.5.1), as explained in section 4.2.1, between around 100 annual t in 2001 and 2006, and a minimum of 42 t in 2007, and a maximum of 819 t in 2012 (value for 2013 incomplete, include landings from March to July). It seems that at least until 2010 landings were under-reported. In 2013 the quota was fixed to 819 tonnes , which corresponds to the status quo. No problems were encountered by the boat seiners to attain the monthly

1 http://www.icm.csic.es/rec/lleonart/Videos/Vessel7.wmv 2 http://www.icm.csic.es/rec/lleonart/Videos/vessel10.wmv 3 http://www.icm.csic.es/rec/lleonart/Videos/Vessel172.wmv

36 quotas that were fixed to reach 819 t by the end of the fishing season. This fact would point to no decrease in sand eel abundance in relation to 2012. But the landings fluctuations could be a result not only of under- reporting, but also due to natural fluctuations of the abundance of the species. Thus, for instance, in the North Sea and for Ammodytes marinus, warm winter conditions have been related to poorer than average recruitment (Arnott & Ruxton, 2002). The fishermen participating in the scientific study have commented that this is the case, that there are some "good years" followed by "bad years". No information is available on this regard, which might be object of future research. This question opened, it is important to keep in mind that the scientific study seems to have been conducted in a period of high abundance of sand eel.

900 Sand eel landings 800 700 600 (t) 500 400

landings 300 200 100 0 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012

2013(Jul) Fig. 4.5.1. Sand eel landings over 2000- 2013 (until July).

In order to know whether the fluctuations in the landings were not just a consequence from under- reporting, but might really indicate changes in the species abundance, three boat seiners were selected to see whether their landings were coincidental with those reported for the whole fleet; their activity (fishing days) and fishing season CPUE (kg/day) over 2000-2013 are also shown (Fig. 4.5.2). Vessel 13, based in Blanes was selected because it was the boat seiner with highest recorded landings over 2000-2013; vessels 14 and 3 were chosen as representative of the fishing ports of Blanes and Arenys, the ports with highest sand eel landings over the whole period. Focusing in the second half of the period, since 2007 the CPUEs displayed an increasing trend, linked to increasing landings until 2011. In 2012 the CPUEs were very similar for the three boat seiners, and in 2013 it was the same for the three vessels, as a result of the fishing regulations implemented since July 2012. It is worth noting that the three vessels reached the quotas that were monthly fixed. Both the increasing CPUE trend in the last years and the vessels reaching the quotas suggest high abundance of the resource at present. The monthly landings (t) and CPUE trend is presented for the period 2000- 2013 in Figs. 4.5.1 (CPUE expressed as kg caught by day and vessel) and 4.5.2. (CPUE expressed as number of individuals caught by day and vessel). Left axis scale, which corresponds to CPUE, is the same for the whole period, to ease comparison among fishing seasons. In a fishery as that of sand eel in the Catalan Coast, basically based on the exploitation of one cohort along the fishing season, it would be to be expected high landings and CPUE at the start of the fishing season, gradually decreasing as the season advances. Despite under- reporting, this seemed to be the trend displayed by the monthly landings

37 (Figs. 4.5.3 and 4.5.4). This pattern was more evident when CPUE was expressed as numbers by day and vessel. In years of low reported landings (e.g. 2001, 2006, 2007), landings quickly decreased and CPUE was very low during the whole fishing season.

140000 Landings by fishing season and vessel 120000

100000

80000

(kg) 13 60000 14 40000 3 20000

0 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013(July)

250 days with sandeel sale at the auction,

200 by fishing season and vessel

150 13 days 100 14 3 50

0 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013(July)

800 CPUE (landings (kg)/days with sandeel sale at the auction) 700 600 500

400 13 (kg/day) 300 14 200 3 100 0 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012

2013(July) Fig. 4.5.2. Landings, fishing days and CPUE (kg/day) for three selected vessels over 2000- 2013(July). Vessel numbering as in Annex I.

A common trait in most of the fishing seasons was the increase of landings by the end of the fishing season, in November, which could be interpreted as resulting from low fishing activity in the previous months as consequence of low yields. It is interesting observing the effect of the management measures applied from July 2012. The fishing effort was reduced, as demanded by the EC, to only 10 vessels allowed to go fishing daily. To this aim a calendar of activity was established for the

38 600 monthly CPUE (kg/day) 90 600 60 monthly CPUE (kg/day) 600 monthly CPUE (kg/day) 100 monthly landings (t) 80 monthly landings (t) 90 500 500 monthly landings (t) 50 500 70 80 2000cpue 70 400 2000landings 60 400 2005cpue 40 400 2010cpue 60 50 2005landings 2010landings 300 300 30 300 50 40 40 200 30 200 200 20 30 20 20 100 100 10 100 10 10

0 0 0 0 0 0 123456789101112 123456789101112 123456789101112

600 30 600 140 monthly CPUE (kg/day) 600 monthly CPUE (kg/day) 35 monthly CPUE (kg/day) monthly landings (t) monthly landings (t) 120 500 25 500 monthly landings (t) 30 500 2011cpue 2006cpue 25 100 400 2001cpue 20 400 400 2011landings 2001landings 2006landings 20 80 300 15 300 300 15 60 200 10 200 200 10 40 100 5 100 100 5 20

0 0 0 0 0 0 123456789101112 123456789101112 123456789101112 600 100 monthly CPUE (kg/day) 600 14 600 monthly CPUE (kg/day) 140 90 monthly CPUE (kg/day) monthly landings (t) 500 monthly landings (t) 120 80 500 monthly landings (t) 12 500 2002cpue 70 400 10 100 2002landings 400 2007cpue 400 60 8 80 300 50 2007landings 300 300 40 6 60 200 30 200 200 4 2012cpue 40 20 100 2012landings 100 2 100 10 20 0 0 0 0 0 0 123456789101112 123456789101112 123456789101112 600 60 monthly CPUE (kg/day) 600 monthly CPUE (kg/day) 45 600 monthly CPUE (kg/day) 140 monthly landings (t) monthly landings (t) 40 500 50 monthly landings (t) 500 500 120 35 2003cpue 2008cpue 400 40 100 2003landings 400 2008landings 30 400 25 80 300 30 300 300 20 60 200 20 200 15 200 40 10 100 10 100 2013cpue 100 20 5 2013landings 0 0 0 0 0 0 123456789101112 123456789101112 123456789101112

600 80 600 monthly CPUE (kg/day) 80 monthly CPUE (kg/day) monthly landings (t) monthly landings (t) 70 70 500 500 2009cpue 2004cpue 60 2009landings 60 400 400 2004landings 50 50

300 40 300 40

30 30 200 200 20 20 100 100 10 10

0 0 0 0 123456789101112 123456789101112 Fig. 4.5.3. Monthly CPUE (kg/day per vessel; left axis; scale the same for the whole series) and landings (in t; right axis) over the fishing seasons 2000- 2013, until July.

39 90 monthly CPUE (num*1000/day) 60 monthly CPUE (num*1000/day) 100 1000 monthly CPUE (num*1000/day) monthly landings (t) 80 1000 1000 monthly landings (t) 90 monthly landings (t) 50 70 80 800 2000cpue 800 800 2010cpue 70 2000landings 60 2005cpue 40 2005landings 2010landings 60 600 50 600 600 30 50 40 40 400 400 400 30 20 30 20 20 200 200 200 10 10 10 0 0 0 0 0 0 123456789101112 123456789101112 123456789101112 monthly CPUE (num*1000/day) 140 monthly CPUE (num*1000/day) 30 monthly CPUE (num*1000/day) 35 1000 1000 monthly landings (t) 1000 120 monthly landings (t) 25 monthly landings (t) 30 800 800 2011cpue 100 800 25 2001cpue 20 2006cpue 2011landings 2006landings 2001landings 80 600 20 600 15 600 60 15 400 400 10 400 40 10 200 200 5 200 20 5

0 0 0 0 0 0 123456789101112 123456789101112 123456789101112 100 monthly CPUE (num*1000/day) 14 140 1000 90 monthly CPUE (num*1000/day) monthly CPUE (num*1000/day) monthly landings (t) 1000 1000 80 monthly landings (t) 12 monthly landings (t) 120 800 2002cpue 70 800 800 2002landings 2007cpue 10 100 60 600 8 50 600 2007landings 600 80 40 6 400 60 400 30 400 4 2012cpue 40 200 20 2012landings 200 200 10 2 20

0 0 0 0 0 0 123456789101112 123456789101112 123456789101112

60 45 monthly CPUE (num*1000/day) monthly CPUE (num*1000/day) monthly CPUE (num*1000/day) 140 1000 1000 monthly landings (t) monthly landings (t)40 1000 monthly landings (t) 50 120 35 2008cpue 800 2003cpue 800 40 2008landings 30 800 100 2003landings 600 600 25 80 30 600 20 400 400 60 20 15 400 10 40 200 200 10 200 2013cpue 5 20 2013landings 0 0 0 0 0 0 123456789101112 123456789101112 123456789101112 monthly CPUE (num*1000/day) 80 monthly CPUE (num*1000/day) 80 1000 1000 monthly landings (t) 70 monthly landings (t) 70 2009cpue 800 2004cpue 60 800 2009landings 60 2004landings 50 50 600 600 40 40

400 30 400 30

20 20 200 200 10 10

0 0 0 0 123456789101112 123456789101112 Fig. 4.5.4. Monthly CPUE (number of individuals*1000/day per vessel; left axis; scale the same for the whole series) and landings (in t; right axis) over the fishing seasons 2000- 2013, until July.

20 boat seiners participating in the scientific study from August 2012 to July 2013, in such a way that each vessel active one week remained in port the following week. In all, it is worth noting two results, regarding catches (in this period, with strict control of the fishing activity, landings correspond to catches) and CPUE. In 2012, the activity of the fleet was low from March to May. The effect of this low activity in the first months of the fishing season was reflected in high landings from June, higher than in the previous seasons, with a much lower fishing effort. In 2013, CPUE expressed both as daily catch by vessel in kg and in number was the highest of the whole data series 2000-2013.

40 Stock- Recruitment relationship Stock-Recruitment relationship was explored assuming that catches and CPUE can be taken as proxy for the species abundance. Furthermore, from the monthly length distributions and the biological sampling, it can be concluded (see below under "Data from the scientific study") that i) most of the recruitment arrives to the ground in February; ii) catches in December consist of individuals that have reached the size-at- first-maturity; and iii) in December, the population was spawning. Accordingly, catches and CPUE at the end of the fishing season in December (t) were considered as a proxy for the Spawning Stock Biomass; and catches and CPUE in March (t+1) were considered as a proxy for recruitment.

catch Dec(t) vs catch March (t+1) catch Dec(t) vs catch March (t+1) 100 (a) 200000 (b) Dec2012‐ 180000 March2013 Dec2012‐ 80 160000 (t) March2013 ‐ 140000

60 (thousands)

‐ 120000 100000

March(t+1) 40 80000 60000 March(t+1)

Catch 20 40000 20000 Catch 0 0 0 10203040 0 5 10 15 20 25 30 35 Catch Dec(t)‐ (t) Catch Dec(t)‐ (t)

CPUE Dec ( t) vs CPUE March (t+1) (c) CPUE Dec ( t) vs CPUE March (t+1) 600 (d) 200000 /

500 180000 vessel) Dec2012‐ 160000 /

Dec2012‐ 400 March2013 140000 March2013 120000 (numbes/day

(kg/day 300 100000

thousands) 80000

(t+1)

(t+1) 200 60000 100 40000 vessel; March

March 20000 in

in 0 0 0 100 200 300 400 500 CPUE 0 2000 4000 6000 8000 10000 12000 14000 CPUE CPUE in Dec (t) (kg per day and vessel) CPUE in Dec (t) (numbers per day and vessel; thousands)

Fig. 4.5.5. Stock- Recruitment: relationship between catches and CPUE at the end of the fishing season in December (t) and catches at the beginning of the following fishing season in March (t+1).

Despite the under-reporting which seems to have taken place until the most recent years, and therefore results should be taken with caution, from Fig.4.5.5 it seems that in the study area there is a clear link between the yield at the end of the fishing season in December, which corresponds to mature individuals spawning, and that at the beginning of the fishing season the following year in March, which consist of small individuals recently recruited to the fishing ground. In all four cases shown in Fig.4.5.5, with catches in weight or in numbers, and CPUE in kg or numbers per day and vessel, the value corresponding to Dec2012-March2013 is clearly separated from all the other points of the data series. The high yields obtained still at the end of the 2012 fishing season can be interpreted as a consequence of the lower activity of the fleet, which remained moored for several weeks. Later, the relative high abundance of sand eel in December 2012 resulted in high yields in March 2013. This is an interesting result, which shows that the species quickly responds to management measures.

41 Biomass estimation. Leslie Method In populations in which fishing effort removes enough individuals to significantly reduce the catch per unit of effort, depletion models, such as the Leslie method, may be employed for population estimation. All are based on the principle that a decrease in the CPUE as the population is reduced or depleted is directly related to the extent of population decrease. The population size can be estimated by sampling over a number of time intervals and plotting a regression line of C/f on cumulative catch (Leslie method; Leslie and Davis, 1939). The regression line is then projected to the intercept, the initial population size at the beginning of the fishing season. The biological sampling of sand eel carried out from August 2012 to July 2013 confirmed that there is no further incorporation of recruits after the start of the fishing season, on March 1st. We applied method proposed by Leslie to the monthly CPUE, by fishing season (shown in Fig. 4.5.4), for the whole studied period 2002- 2013. Results are shown in Fig.4.5.6, with the fitted regression lines, and Table 4.5.1, with the estimated population (B0) at the beginning of the fishing season. B0 was much higher by the end of the studied period, from 2010 onwards.

Table 4.5.1. Sand eel population size (in numbers, thousands) at the beginning of the fishing season.

2000 2001 2002 2003 2004 2005 2006 440000 140000 530000 300000 470000 360000 130000 2007 2008 2009 2010 2011 2012 2013 60000 250000 500000 670000 840000 1050000 1010000

42 2000 2005 2010 450 400 (March excluded) y = ‐0,0014x + 509,57 400 350 R² = 0,8889 500 350 450 300 300 400 250 250 y = ‐0,0012x + 533,46 350 R² = 0,8895 200 300 200 250 y = ‐0,0011x + 743,61 150 150 200 R² = 0,9278 100 100 150 50 50 100 0 0 50 0 100000 200000 300000 400000 500000 0 100000 200000 300000 400000 0 0 200000 400000 600000 800000 2001 2006 250 2011 350 700 300 200 600 250 500 150 200 y = ‐0,0046x + 620,35 y = ‐0,0024x + 348,18 400 y = ‐0,0009x + 761,76 150 R² = 0,9568 R² = 0,9441 100 R² = 0,9785 300 100 200 50 50 100 0 0 0 40000 80000 120000 160000 0 0 50000 100000 150000 0 200000 400000 600000 800000 2007 800 2002 2012 250 (May excluded) 700 (March excluded) 600 600 200 500 500 y = ‐0,002x + 1065,9 R² = 0,912 150 400 400 y = ‐0,0056x + 351,49 300 100 R² = 0,9009 300 y = ‐0,0006x + 630,22 200 200 R² = 0,738 50 100 100 0 0 0 0 200000 400000 600000 0 10000 20000 30000 40000 50000 60000 70000 0 200000 400000 600000 800000

2003 2008 2013 400 (March excluded) 1400 350 300 1200 300 250 1000 250 200 200 800 y = ‐0,0016x + 491,27 y = ‐0,0016x + 400,9 150 R² = 0,9228 150 600 R² = 0,8257 100 100 400 50 50 200 y = ‐0,0014x + 1415,1 0 R² = 0,8401 0 0 50000 100000 150000 200000 250000 300000 0 0 50000 100000 150000 200000 250000 0 200000 400000 600000 800000 2004 2009 (March excluded) (March excluded) 500 350 450 400 300 350 250 300 200 250 y = ‐0,0015x + 718,24 y = ‐0,0008x + 406,48 200 R² = 0,9154 150 R² = 0,9903 150 100 100 50 50 0 0 0 100000 200000 300000 400000 500000 0 100000 200000 300000 400000 500000 Fig. 4.5.6. Leslie depletion model. Monthly CPUE (number of individuals in thousands per day and vessel), left axis, plotted against the cumulative catch (number of individuals).

Data from the scientific study The length frequency distributions cover the period August, 2012 – July, 2013. This period actually corresponds to two halves of two seasons. The only way to work with those data is assuming steady state and assuming one season from the two halves. Considering the species is short lived the errors and biases generated by this assumption are acceptable.

43 It should be noted that the mean length increases along the fishing season. In the figures this progression is presented with intervals correspondent to one standard deviation (covering 68.28% of the cases). The months of January and February the fishery is closed, but the length sampling was taken, these months without catch the intervals are not shown. The mean length increases from 5.63 cm in February to 10.39 in January. The meaning is that most of recruitment arrives to the ground in February. Consider than the smallest specimen caught was 3.5 cm (already showing adult phenotype) and the larvae identified by Sabates et al. (1990) was 2 cm.

Mean lengths Mean lengths

12 12

11 11

10 10

9 9

8 8 cm cm 7 7

6 6

5 5

4 4 July 2013 May 2013 July 2013 May 2013 April 2013 April April 2013 April June 2013 June 2013 March 2013 March 2013 August 2012 August 2012 October 2012 January 2013 October 2012 January 2013 February 2013 February 2013 November 2012 December 2012 November 2012 December 2012 September 2012 September 2012 successive months artificial season

Fig. 4.5.7.Average length from monthly sampling, bars indicating one standard deviation. January and February have not error bars because are special samplings during the closes season. At left the actual time schedule, at rigth the reconstruction of a “pseudoseason”. A number of 90 length frequency distributions were obtained, including 33916 measurements, covering the whole fishing period (two monthly samples) and 6 ports. Each sample was expanded to the total catch of each period, and eventually added to obtain a single distribution which represents the length frequency distribution of the whole catch (i.e. the total number of individuals caught of every length interval). Although the length measurements were taken to the next 0.5 cm a bias was observed: the classes of the type [x+0.5, x+1] were underestimated in relation to the classes [x+1, x+1.5], in order to avoid artifacts from this bias, 1 cm [x+0.5, x+1.5] length classes were used. In the figure a comparison between both length frequencies, 0.5 cm class and 1 cm class are compared.

250

200

150 0.5 cm 1 cm

Millions 100

0 0 5 10 15 20 cm

Fig. 4.5.8. Length frequency distribution using 0.5 cm and 1 cm classes

44 Length frequency distribution of the period August (2012)- July (2013). It represents the whole catch (866.2 tons) Table 4.5.2. Lenght frequency distribution and proportion of matures in base to 1 cm class Number Proportion Length class caught of matures lower mean N 3.5 4 481 054 0 4.5 5 54 677 054 0 5.5 6 222 370 358 0 6.5 7 186 795 786 0.7 7.5 8 117 065 328 1 8.5 9 80 421 336 1 9.5 10 50 276 316 1 10.5 11 21 942 593 1 11.5 12 6 889 450 1 12.5 13 1 813 712 1 13.5 14 255 711 1 14.5 15 942 1

The mean length of the catch along the fishing season is 7.31 cm, the lower limit of the length class fully represented (lc or L’) is 5.5 cm, the minimum and maximum observed lengths are 3.5 and 14.6 cm. All individuals are mature at 7.5 cm. It is necessary to add some comments about the growing trend (left part) of the length frequency distribution. In trawl fisheries, the left, growing branch is interpreted as the sizes below the mode are not fully recruited to the gear. In the case of sand eel gear this is not so clear, and the left increasing branch (comprising the two first length classes) could be consequences of three different factors: o Selectivity. Although in the cod-end the escarpment is hardly possible, it is true that the bands of the gear can allow the escapement of the smaller individuals. Some selectivity regarding the smaller individuals is possible. o Availability (sensu FAO glossary) or accessibility (sensu Laurec and Le Guen, 1981). A fraction of the small individuals, are not available during the fishing season because they are not yet recruited to the fishing ground. o Vulnerability (sensu Laurec & Le Guen, 1981). Small fish behavior contributes to avoid being caught.

Parameter estimation Length-weight relationship There is no particular problem in the calculation of the length-weight relationship parameters. From 5243 individual length-weight measures the parameters a = 0.001937 gr·cm-3 and b = 3.139 were obtained. The formula relating length (l) and weight (w) is w = a·lb.

45 Growth Growth, that is, the parameter set of the von Bertalanffy equation, is of paramount importance in stock assessment. Results on mortalities, biomass estimation and other fundamental indicators are sensitive to growth. In the present case ALK (age-length key) is not available. Although otoliths were extracted and preserved, there were no possibilities of otolith-reading in the project. On the other hand, the bibliography on Ammodytidae growth is scarce, and for Gymnammodytes cicerelus completely absent. For instance, Reay (1970), analysing Ammodytes tobianus and Ammodytes marinus from the Atlantic, finds maximum lenghts of 20 and 23 cm and 7 and 9 age classes. These values are not applicable to the Mediterranean G. cicerelus, since water characteristics are completely different, especially the temperature, still the maximum length observed is 14.6 cm. For sure G. cicerelus has a faster growth rate and a much lower longevity. Hence, length frequency distributions obtained from sampling are an available source of information to obtain growth parameters. The reliability of the growth estimation based on length frequency is limited. The von Bertalanffy growth parameters were estimated using different methods, and using four length frequency data sets: monthly and seasonal, and with length classes of 0.5 and 1 cm. Some of the methods used are those of Froese and Binohalm (2000), and those included in FiSAT II software which includes ELEFAN I, Shepherd’s method, Powell-Wetherall plot and Battacharya’s method (references of these methods in Gayanilo et al. 2005).

A collection of sets of growth parameters [L, K] were obtained (t0 can be considered irrellevant since it does not affect the shape of the growth curve but only a translation through the time axis). The Froese & Binohlan (2000) method allows the calculation of an estimate of L (not K) from the observed maximum length (L = 14.6 in the present case) using a regression formula. The value obtained is 15.48 but the standard error is quite high, giving the confidence intervals at 90% of [11.09, 21.62]. The estimated mean value is lower than the lowest value estimated by the other methods (L = 15.75). It must be said that the goodness of fit of these methdos is quite poor, i.e. the response surfaces are really wide and no clear areas of reliable estimators were found. The use of modal progression using ELEFAN I was found not very reliable as well, giving a K value quite high . The mean length by month of the observed catch during the sampled year was also used. These data do not represent the individual growth, but the average population growth by month. We applied two fitting methdos to these data: ELEFAN I (from FiSAT II) and minimizaton residual mean squares (RMS). These data set fits well with von Bertalanffy growth model and gives a image of a quasi straight growth curve, with a low K and a high L. At this point we would like to note that the meaning of L does not always mean an actual length to with the old specimens approach nearby, but just a non-meaning parameter that, with K, defines the shape of the growth. Hence a set of high L and low K just means a quasi constant growth.

46 The sets [L, K] foud by the different methods are. Table 4.5.3. Different growth estimates L K Shepherd’s method on length frequency distributions 15.75 0.84 ELEFAN I 17.40 1.01 RMS on average lengths 32.51 0.225 ELEFAN I on average lengths 28.5 0.36

According to the first set (low L) the life span is 3 years, the three last sets give a lifespan around 2 years

Growth in length Growth in weight

20 10 18 9 16 8 14 7 Low L(inf) Low L(inf) 12 ~ Average 6 ~ Average 10 RMS 5 RMS 8 ELEFAN I 4 ELEFAN I weight (gr) weight length (cm) observation interval observed interval 6 3 4 2 2 1 0 0 0 0.5 1 1.5 2 2.5 3 0 0.5 1 1.5 2 2.5 3 age (years) age (years) Fig. 4.5.9. Length (left) and weight (right) growth curves

Pedersen et al. (1999) employ two sets of growth parameters for two regions of the North Sea Ammodytes marinus. Values of W (not L) are 19.7 and 16.2 gr. These weights would correspond to 18.9 and 18.0 cm with our length-weight relationships. Values of K are 0.0016 and 0.0024 days-1. Transformed to year-1, are: 0.584 and 0.876. Maturity The estimation of length at first maturity has given a value for L50% of 7.32 cm. This value is much smaller that those found for lesser sandeel Ammodytes marinus in the North Sea, which is between 10 and 12 cm length (Boulcott, 2007). According to the data provided by these authors most of the specimens between 7 and 8 cm are immature. According to Pedersen et al. (1999) A. marinus reaches the maturity at the age of two years. Mortalities In order to assess the stock estimations of natural mortality are also needed. There are not many methods. First of all the natural mortality can be considered as constant along the ages (or lengths) or be a vector with different values for each age or length class. There are not many methods to estimate Natural Mortality (M). FiSAT II provides two procedures, one based on the age of first maturity (Rikhter and Efanov) and other on von Bertalanffy parameters and mean temperature (Pauly). None of them takes into account the length frequency distributions. The age at which 50% of the stock reaches the “massive spawning” fitting a normal accumulative curve was calculated at 0.540 years (length 7.32 cm), according to Rikhter

47 and Efanov model the corresponding M is 2.209. Fitting a log normal accumulative curve the age is 0.523 years, the length 7.14 cm and M is 2.264. The Pauly’s uses the von Bertalanffy growth parameters and the mean annual temperature of the habitat. According to Salat (com. pers. from Salat & Pascual 2006) the mean annual temperature of the area where the sandeel lives and 8-10 m depth is rougly 16.5ºC, within limits of 12º and 24º. The Pauly’s model gives M values of 1.636 (at 16.5º), 1.412 (at 12º) and 1.946 (at 24º). Caddy (1991) proposed an age-inverse function to estimate M from the von Bertalanffy growth parameters. This method neither does use the length frequency distributions, however it provides not a single value but a vector of M per class. The model was fitted using the software PRODBIOM (Abella et al. 1997).

Inverse model (Caddy, 1991)

3.5

2.5

2 M 1.5

0.5

0 00.511.52 age

Fig. 4.5.10. Shape of the curve of inverse model for M

However it is not clear that the large old sandeels (i.e. 14 cm ~1.5 years old) are less vulnerable to predators or starvation than the younger ones (i.e. 5 cm ~0.35 years old). As shown later on, the estimates of total mortality growth with length/age, just the contrary trend to the Caddy’s hypothesis. There are more methods, and likely more reliable, to estimate the total mortality, the total mortality approach can be useful to tune the VPA by adapting the terminal F, and also the M, to obtain the expected total mortality. The calculation of various averages of M, with different criteria of weighting, produces values between 0.983 and 1.536. Summarizing we have obtained a range of M values between 0.983 and 2.264. A rough average gives a possible M around 1.6 Pedersen et al. (1999) use natural mortalities of 0.8 for age class 0 and 1.0 for age class 1, to the lesser sandeel Ammodytes marinus in the North Sea. More methods exist to estimate the Total Mortality Z. The software FiSAT II allows to perform calculations with 6 different methods. Contrary to M, Z is not a direct input in the assessment softwares, but can be useful to check results. The catch curve and the Jones and van Zalinge methods use the length frequency distribution. For these estimations the half centimeter length class has been used.

Table 4.5.4. Different total mortality estimates Model Z Catch curve: 5.5 cm to14 cm (with classes of 0.5 cm) 7.10 Catch curve: 7.0 cm to 13.5 cm (with classes of 0.5 cm) 7.07 Catch curve: 6.5 cm to13.5 cm (with classes of 1 cm) 6.66 Catch curve: 7.5 cm to 13.5 cm (with classes of 1 cm) 6.94 Jones / van Zalinge: points 5.5 to 13.5 7.183 Beverton and Holt (mean length 7.31, lc= 5.5) 5.638 Ault and Ehrhardt (L’=5.5, Lmax=14.6) 5.628 Hoenig, model 1 (tmax=1.8) 2.355 Hoenig, model 2 (tmax=1.8, N=1, tc=0.24) 5.466

These calculations give an average of 6.0. The catch curve assumes constant effort for all classes (Ricker, 1975) hence catch is porportional to catch-per-unit-effort and to the number at sea (assuming also constant catchability), this hypothesis can be assumed for the present fishiery, so the trend of estimated total fishing mortality by class can be also estimated (see figure).

7 y = 0.7421x - 1.975

t 6 Δ

"Z1" - = ln(N2/N1)/ 3

0 5 6 7 8 9 1011121314 length

Fig. 4.5.11.Estimates of Z from the catch curve.

Note the increasing trend of Z by length (or age) class from 2 to 7. This trend can be due to the fishing mortality, natural mortality (in opposition to the Caddy’s assumption of decreasing natural mortality with age/length) or both. Assessment methods and software In order to proceed with the assessment, software VIT (Lleonart and Salat 1992, 1997) has been used. This software performs length cohort analysis (LCA), VPA and other stock assessment estimations assuming steady state. This restrictive hypothesis is necessary since only one season data is available. VIT has been used for many years and proved to be reliable (Rätz et al. 2010). It can be considered a current standard method for many Mediterranean fisheries assessment.

49 This software allows to transform length frequency distributions into age frequency distributions through slicing. Age structured data allows to perform further analysis, especially the projection to the future of the fishery under different management alternatives. However, given the short lifespan of sandeel, this transformation is hardly applicable. The maximum observed age (under the agreed von Bertalanffy growth parameters) is 1.8 years, hence the age frequency distribution presents only two age classes, too few to perform any reliable age-based analysis. Using smaller temporal scale is not advisable because the biological cycle of sand eel is actually annual. Hence LCA using VIT software has been used. Data As mentioned before the length frequency distribution to be analysed is arranged by classes of 1 cm rather than the original 0.5 cm, this allows working with a smoothed frequency distribution and avoiding the sampling biases. To avoid other possible problem with VPA, the two last classes have been added to crate a single class plus, i.e. 13.5+ class. Due to the backward convergence of the VPA, the standard process starts with the last class, assuming, and tuning, a fishing mortality coefficient for that class, named terminal fishing mortality, or Ft. As consequence the last class has an important role on the VPA global results. In the present example the last class (class 14.5) is composed by 942 individuals. Considering that the total individuals caught in the fishing period is 743 million, this 942 is a meaningless small number (one over one million), strongly affected by the sampling variability. The 13.5+ class provides much more stability to the results Assessment scenarios Assessments have been performed under 16 scenarios considering different sets of Natural Mortality and growth. For each scenario four LCA runs have been performed using different Terminal Fishing Mortalities (Ft) (i.e. 2, 4, 6 and 8). That means 64 different LCA runs. In order to facilitate the reading of this document only the results of one scenario, that one appearing to be the more reliable to the authors of this report, is presented, that corresponding to the growth set (L = 15.75, K = 0.84) and M = 2.0. The results of the other scenarios are however commented Results

Effect of Ft. The terminal fishing mortality has only effect on the final part of the F vector. The other indicators are no significantly affected. This is true for all the scenarios. Number of individuals at sea The annual average number of indivuduals per class is represented.

50 Mean annual number at sea

250

200

150

100

number in millions 50

0 0123 age

Fig. 4.5.12.Mean annual number of individuals at sea. In the presented scenario the total annual average number is 753 million. In the set of scenarios these numbers vary between 300 and 1200 million. Note that these figures represent the mean annual numbers, and that the number of individuals in a class (a class encompasses much less than one year) is much larger. The number of recruits, that is, the number of individuals (not the annual average) of the class [3.5-4.5] is around 2200 million. In all the scenarios is between 1000 and 3000. This figure meets with the order of magnitude of the estimates obtained by the Leslie’s method. Lower K and higher M result on more individuals at sea needed to explain catches. Biomass at sea The annual mean biomass at sea is 490 tons for the scenario of reference. Other scenarios is comprised between 200 and 600. Note that, as in the case of numbers, those biomass refers to annual mean, and that in a particular instant could be greater. On the other hand the mortalities (both natural and fishing) are higher than 1, hence the catches can be greater than mean biomass, to comply with the catch equation  ·BFC

Biomass at sea

90 80 70 60 50

tons 40 30 20 10 0 0123 age

Fig. 4.5.13.Mean annual biomass of individuals at sea.

51 As in the case of numbers, a lower K and higher M, produce larger biomasses. The software VIT allows to compute the virgin biomass, although its reliability is not good (Rätz, 2010). For the present scenario the virgin biomass is 1573 tons and the mean current biomass is 31% of it. Fishing mortalities As can be seen in the figure, the terminal fishing mortality has little effect beyond the two last classes

Fishing mortality

9 8 7 6 Ft=8 5 Ft=6 F 4 Ft=4 3 Ft=2 2 1 0 0123 age

Fig. 4.5.14. F by age, from four different terminal F values The crude average of F by class, gives a value of 1.84. The average F weighted by the mean biomass per class, compatible with the catch equation presented above, is 1.74, and considering the natural mortality, that gives a biomass annual turnover of 374%, that means, that every year the biomass is renewed (by growth, recruitment and mortalities) 3.74 times. Other scenarios produce different shapes of F vector. Some of them, the increasing trend by class is much more apparent (according to the trend detected for Z following the catch curves analysis, presented before). In most of the other scenarios the averages of F are higher, reaching in some cases values of 3. In this case, as in the previous, higher Ks, lower Ms, tend to increase the values of estimates of Fs. In all scenarios the values of F for the younger classes are low. Yield per recruit In the chose scenario the yield per recruit appears to be in good shape, with no traces of growth overfishing, with a value of 0.38 grams per recruit (the maximum is 0.383 in factors of 1.3 times of the current F value).

52 Yield per recruit

0.5

0.4

0.3

grams 0.2

0.1

0 00.511.52 F factor

Fig. 4.5.15. Yield per recruit.

The yield per recruit from other scenarios, specially those with high K and low M, can produce images of growth overexploitation with yields higher (i.e. 0.75 grams per recruit). Discussion of the assessment Sand eel is a short lived species. The age of the population at sea is below 1 year 99% in number of individuals and 96% in biomass. This characteristic has several consequences regarding the stock assessment: (i) the stock is highly dependent on the recruitment, 26% of the individuals at sea belong to the first class (3.5-4.4 cm length), and (ii) mortalities are very high. The stock assessment models that can be used with the actual data availability are highly sensitive to the biological parameters, in particular growth and natural mortality.

Effect of Ft. As it is known, the terminal fishing mortality has no significant effect on number and biomass estimations. The effect on F vector is visible but low and only in the two last classes. Effect of growth The growth has a heavy effect on the results of LCA. Although both, L and K, affect the assessment, K appears to be more impact and LCA results are very sensitive to it. In general a high K produces a shape of a small populations heavily exploited, while a low K does the opposite. For this reason is highly recommended to refine in the future the estimates of the von Bertalanffy growth parameters, is possible analising the daily otolith increments. Effect of natural mortality Natural mortality has a similar effect to K, but in the contrary. Low Ms contribute to give an image of small populations heavily exploited. So effort to progress in M estimates is highly recommended.

53 Conclusions of the assessment According to the assessment scenarios considered it appears that the sand eel fishery of the two half periods (2012-2013) is quite healthy. In the worst parameter combination a slight growth overfishing could appear. However no traces of recruitment overfishing have been detected. The state of the stock appears to be in a good shape but with a significant limitation of reliability. In that case, and waiting for further data and better parameter estimates, it is advisable to maintain the status quo of the last year for which an effort reduction to a half and a TAC has been established. Furthermore monthly harvest control rules to keep the fishery under continuous observation is highly recommended. In 2013, the boat seiners did not encounter problems to attain the monthly quotes fixed to reach 819 t by the end of the fishing season, which would suggest that sand eel abundance did not decrease in relation to 2012. A status quo quota for 2014, of 819 t is proposed, the same quota as in 2012 and 2013. In the coming years, the fishing season quota will fixed at the start of the season, based on the results of the previous fishing season. Gimnammodytes cicerelus reproduction period in the area extends from November to February and at the end of the fishing season in mid- December the population consists of individuals that have attaint the size-at-firt-maturity. Therefore, it is advisable to maintain the timing of the currently implemented closed season, from mid- December to the end of February. Since the yield at the start of the fishing season has been shown to be related to the yield at the end of the previous fishing season (SSB-Recruitment relationship), it is advisable not to modify the current closed- season period, from 16 December to the end of February.

54 PART II: GOBIDS

5 BIOLOGY OF GOBIDS

5.1 Taxonomy Aphia minuta (Risso, 1810)

Diagnosis: Dorsal spines (total): 4 - 6; Dorsal soft rays (total): 113; Anal spines: 1; Anal soft rays: 11 - 15. Vertebrae 26-28 (Whitehead et al , 1986.). Aphia minuta is a small species no more than 6 cm long (Tortonese, 1975) with a short lifecycle and rapid maturation of the gonads. The specimens present a long body flattened laterally. The scales are cycloid and easily lost. There are no scales on the nape of the neck or the first dorsal fin. The swimbladder is evident and persistent and the food canal is straight and short. The adults are white, yellowish or pink; the body is transparent with a few black chromatophores. In proximity to the opercules a red spot can be observed due to the blood of the gills, visible because of the animal’s transparency. This species presents sexual dimorphism: the males have a larger head, uneven teeth, a higher caudal peduncle and the fins are more developed, especially the ventral ones. Distribution: Aphia minuta is spread throughout the Atlantic Ocean from Gibraltar to the Norwegian coasts, the North Sea and the western Baltic Sea. It is also present all over the Mediterranean basin including the Black Sea (Miller, 1986). Biology: It is a coastal species, pelagic in the larval and young stage. During sexual maturity the organisms acquire demersal-benthic habits.

55 Crystallogobius linearis (Düben, 1845)

Diagnosis: Dorsal spines (total): 2 - 3; Dorsal soft rays (total): 18-20; Anal spines: 1; Anal soft rays: 20 - 21. Patterns of sensory papillae require detailed description. Pronounced sexual dimorphism. Anterior nostril a short tube. Pectoral fin uppermost rays within membrane. Males: with prominent front canine teeth; pelvic disc complete and deep; 1st dorsal with only 2 with rays. Females: pelvic disc reduced or lacking; 1st dorsal absent or rudimentary. Vertebrae 30 (29-31) (Miller, 1986). Distribution: Eastern Atlantic: Lofotens, Norway, to Gibraltar. Also known from the Mediterranean Sea. Eastern Central Atlantic: Madeira Island (Wirtz et al., 2008). Biology: This occasionally territorial species occurs in coastal waters, over shell, sand, or mud bottoms; males bottom-living during breeding season. Feed on zooplankton (Wheeler, 1992). Spawning takes place when 1 year old. Adults die afterwards. Eggs are laid in the empty tube-worms and are guarded by the male (Muus and Nielsen, 1999). Eggs are pear-shaped (Miller, 1986).

Pseudaphya ferreri (0. de Buen & Fage, 1908)

Diagnosis: Teeth size does not differ markedly between sexes. Dl V, D2 I + 7-10, A I + 9-10, P 15-16. Scales in lateral series 25-30. Vertebrae 30. Colour: body transparent, with rosy stippling on sides, head and bases of median fins; caudal fin base with large triangular dark spot. Size: to 3.5 cm (Miller, 1986). Distribution: It is found in the Mediterranean Sea in the western basin and the Adriatic Sea. Habitat: nektonic, over sandy beaches. Biology: The females mature to 26-27 mm. Reproduction in June.

56 5.2 Length-weight relationship and length frequency Aphia minuta Length-weight relationship Figure 5.2.1 gives the length-weight relationship for Aphia minuta whole population. Positive allometric growth was observed in species.

Aphia minuta y = 0,0028x3,4911 R² = 0,959 0,900 0,800 0,700

gr 0,600 0,500

weight 0,400 0,300 Total 0,200 0,100 0,000 0123456 Total length cm Figure 5.2. 1. A. minuta length-weight relationship (a and b parameters) obtained for the whole study period.

Length frequency The monthly length-frequency distribution in the catches of A. minuta ranged between 2 and 5 cm, with mean size increasing throughout the fishing season from December to May. (Fig. 5.2.2). No clear growth pattern can be observed on length frequency distribution.

December'12 April'13 n=421 0,6 n=150 0,4 0,3 0,4 0,2 frequency frequency

0,2 0,1 Relative Relative 0 0 1,5 2 2,5 3 3,5 4 4,5 5 5,5 1,522,533,544,555,5 Tl (cm) Tl (cm)

February'13 May'13 n=269 0,3 n=300 0,6

0,2 0,4 frequency frequency

0,1 0,2

0 0 Relative 1,5 2 2,5 3 3,5 4 4,5 5 5,5 Relative 1,522,533,544,555,5 Tl (cm) Tl (cm)

March'13 Mean length n=268 0,6 December 2,8033333 January 0,4 February 3,4199424 frequency 0,2 March 3,4981343 April 3,5427553 0 Relative 1,5 2 2,5 3 3,5 4 4,5 5 5,5 May 3,8252788 Tl (cm)

Figure 5.2.2. Monthly length-frequency distribution (December 2012 to May 2013) of A. minuta (n number of individuals sampled) and summary of mean length by month.

57 Crystallogobius linearis Length-weight relationship Figure 5.2.3 gives the length-weight relationship for C. linearis whole population. Positive allometric growth was observed in species.

Crystallogobius linearis 0,450 y = 0,0043x2,8639 0,400 R² = 0,8468 0,350 gr 0,300 0,250 weight

0,200 0,150 Total 0,100 0,050 0,000 012345 Total length cm Figure 5.2. 3. C. linearis length-weight relationship (a and b parameters) obtained for the whole study period.

Length frequency The monthly length-frequency distribution in the catches of C. linearis ranged between 1 and 4 cm. Mean size do not show changes throughout the study period and not growth pattern can be observed on length frequency distribution. (Fig. 5.1.4).

January'13 April'13 n=430 0,6 n=300 0,4 0,3 0,4 0,2 frequency frequency 0,2 0,1 0 0 Relative 1 1,5 2 2,5 3 3,5 4 4,5 Relative 1 1,5 2 2,5 3 3,5 4 4,5 Tl (cm) Tl (cm)

February'13 May'13 n=307 n=197 0,5 0,4 0,4 0,3 0,3 0,2 frequency frequency

0,2 0,1 0,1 0 0 Relative Relative 1 1,5 2 2,5 3 3,5 4 4,5 1 1,5 2 2,5 3 3,5 4 4,5 Tl (cm) Tl (cm)

March'13 n=200 Mean length 0,6 December 0,4 January 2,2248927 February 2,6530613 frequency 0,2 March 2,155 0 April 2,5267442 Relative 11,522,533,544,5 May 2,5454545 Tl (cm)

Figure 5.2.4. Monthly length-frequency distribution (December 2012 to May 2013) of C. linearis (n number of individuals sampled) and summary of mean length by month.

5.3 Reproduction Aphia minuta Available data on reproduction are limited and somewhat contradictory, indicating a rather varied spawning season. In Majorca (Iglesias and Morales-Nin found that the breeding season extended from December to April with a peak in March. After a single reproduction at 5-6 months of age, most of the specimens disappeared from the fishing areas. Recruitment to the fishing area occurred in late December and early January (14-24 mm TL, age 2-3 months). On the other hand, the hatch date back-calculated from the age in days and the date of capture of individuals of A. minuta during the fishing season, indicated a spawning peak in autumn (September-October), six months after the peak of observed spawning. Other studies report spawning season in April in the northern Tyrrhenian sea (Baino et al, 1996), in May-August in the Adriatic sea (Froglia and Gramitto, 1989) and from June to August in the Atlantic ocean (Arruda et al 1993). In our study some mature females were found in March and May (fig. 5.3.1).

Figure 5.3.1 Aphia minuta mature female from 17/04/2013 and 19/03/2013 respectively.

Crystallogobius linearis

Spawning probably occurs in the summer season, from May to August in the north Atlantic (Oslofjord) and from July to September in the Mediterranean (Gulf of Neaples) (Padoa, 1953; Miller, 1986). The observations of La Mesa (2001) regarding hatch date distribution, obtained by the back calculation of otolith ageing data, indicate a long breeding season of at least 8 months for C.linearis (from October to May)

Figure 5.3.2 C. linearis mature female from 17/04/2013). Eggs can be observed by transparency.

59 6 GOBIDS FISHERY

6.1 Structure of the gear and fishing techniques Little goby, generically known as “llengüeta” are transparent goby (Aphya minuta) and crystal goby (Cristalogobius linearis), can only be fished with the boat seine named “sonsera”. This gear is also used for sand eel (Gymnammodites cicerelus y G. semisquamatus) fishery (see chapter 4.1) The “sonsera” is the only gear authorized to exploit both species of gobids off the Catalan coast. By monthly observations on board the authorized fishing boats during the scientific study, from December 2012 to May 2013 the distribution of the fishing grounds of transparent goby and crystal goby visited by this fleet was determined. The fishery of the two gobids is mainly distributed at muddy or sandy-muddy habitats. Aphya minuta is fished between 7 and 12m in the southern fishing grounds, basically near Barcelona’s port coast, whereas Cristalogobius linearis is mainly distributed in northern fishing grounds and presents a deeper bathymetric range, being normally fished between 30-50m depth. The fishing activity must be carried at these fishing grounds and it is forbidden to fish on beds of phanerogams or in rocky bottoms. Structure of the fishing gear (see chapter 4.1) The “sonsera” is a net gear and the structure is based on two long lateral wings and a bag between of the wings including the codend. The dimensions of these structures are as follows:  Maximum length of wings: 125 m.  Maximum height of wings: 35 m.  Maximum length of codend: 30 m.  A rope no longer than 100m at the end of each wing.

The draw in Figure 6.1.1 shows the structure of the boat seine “sonsera”.

Figure 6.1.1. Drawing of the boat seine “sonsera” characteristics The mesh size decreases from the end of the wing (100 mm; 4 Ppp) to the net mouth (16 mm; 24 Ppp). The mesh size of the codend decreases from the mouth (33 mm; 12 Ppp), to its lower white portion of the mesh of the codend (no less than 2mm; 200 Ppp). A cylindrical net extension is found at one end of the codend and sometimes another

60 extension can be found at the other end. The catch is removed from these extensions. The above sizes are the minimum ones for the ends of each gear section. However, the wings and the codend constructive characteristics as well as the mesh size configuration may vary according to the habits and customs of each fishermen and net builders. The wings have a leadline with large number of weights along the net bottom (a maximum of 6 weights per m; maximum 250g each weight), and a floatline along the top of the net to provide flotation in order to achieve a positive buoyancy during the dropping operation (See figures of chapter 4.1) Regarding the crystal goby (Crystalogobius linearis) due to the geographic and bathymetric features of the fishing grounds of the northern area, between Blanes and L’Estartit, where the goby is normally fished between 30-50m depth certain variability in the dimension of the “sonsera” is permitted The crystal goby (Crystalogobius linearis) is normally fished between 30-50m depth due to the geographic and bathymetric features of the fishing grounds of the northern area, between Blanes and L’Estartit. Therefore, in the dimension of the “sonsera” is allowed:  A rope of 200m length at the end of each wing

Fishing techniques The fishing technique has been described, and at the same time, the impact on the marine environment of this fishery operation has been estimated by the observations on board carried out during the scientific study in all the ports where there is “sonsera” fishing activity devoted to both gobids. The fishing process is the same that the one followed with fishing of sand eel, so the description of fishing techniques has been already detailed in chapter 4.1. (See Video 44). Similarly to sand eel, at the end of this fishing process the by-catch species are separated from the target species and are returned to the sea alive. They are extracted from the containers where the total catch is being placed or by using sieves in which by- catch species are retained (Figure 6.1.1).

Figure 6.1.2. Sieving the by-catch from crystal goby fishery

4 http://www.icm.csic.es/rec/lleonart/Videos/Fishingtechniques.wmv

61 6.2 Boat seine fleet and landings Boat seine fleet The information on the boat seine fleet is presented in Part I- section 4.2. As explained in that section, it is worth highlighting that in the study area the activity of the boat seine fleet is driven by sand eel (Table 4.2.1 in that section). Historically, only a small number of boats, four to six, targeted gobid species (i.e. at least around 20 fishing days per fishing season), and the fishing season extended from November to May. The last gobids fishing season was shortened, from mid- December 2012 to the end of February 2013, the same period when the sand eel fishery was closed. Landings and activity (fishing days) in this last fishing season 2012-2013 correspond to four boats. Landings Data on transparent goby (Aphia minuta) and crystal goby (Crystallogobius linearis) landings and activity of the boat seine fleet were obtained from the daily slips from the sale at the auction that takes place upon the arrival of the vessels at port (data source: fishing statistics elaborated by the Fisheries Department of the Generalitat de Catalunya). Data were available on daily landings, separately for each species, by vessel, for the period 2000- 2013 (2599 records).

4500 Aphia minuta 14000 Cristallogobius linearis 4000 12000 3500 10000 3000 8000 2500 kg kg 2000 6000 1500 4000 1000 500 2000 0 0 2013 2013 2012 2012 2011 2011 2010 2010 2009 2009 2008 2008 2007 2007 2006 2006 2005 2005 2004 2004 2003 2003 2002 2002 2012 ‐ 2012 ‐ 2011 ‐ 2011 ‐ 2010 ‐ 2010 ‐ 2009 ‐ 2009 ‐ 2008 ‐ 2008 ‐ 2007 ‐ 2007 ‐ 2006 ‐ 2006 ‐ 2005 ‐ 2005 ‐ 2004 ‐ 2004 ‐ 2003 ‐ 2003 ‐ 2002 ‐ 2002 ‐ 2001 ‐ 2001 ‐ Fig. 6.2.1. Transparent goby (left) and crystal goby (right) landings (kg) in the Catalan Coast over the fishing seasons (November to May) 2001-2002 to 2012-2013 (mid- Dec to February in 2012- 2013).

The boat seine fleet operates in the central and northern Catalan Coast (i.e. from Barcelona to the north). Nevertheless, transparent goby is fished in the southern study area, near Barcelona, close to the mouth of River Llobregat; and crystal goby is fished a little northwards, close to the fishing port of Blanes. Over the studied period, the annual landings of both species fluctuated markedly. Transparent goby landings varied between around 0.5 t in 2006-2007 and 4 t in 2005-2006; and those of crystal goby, between 12.4 t in 2003-2004 and landings practically nil since 2006-2007. No explanation is available as for whether the decrease in crystal goby landings is a consequence of a change in the fishermen's strategy or consequence of under-reporting (Fig. 6.2.1). During the sampling on board from August 2012 to July 2013 only just a few individuals of Crystallogobius linearis were caught. The explanation the fishermen offered for the absence of Ferrer's goby in the catches was that this species is jointly fished with sand eel in certain fishing grounds. Since the target species of the sampling was sand eel, the fishing grounds that were visited were those with presence only of sand eel.

62 Fishing days, per fishing season Historically, the fishing season extended from November to May, that is, partly overlapping with the sand eel fishing season (March to mid- December). The unit of effort considered in this study is the number of fishing days (i.e. the sum of the number of days each boat seiner sold gobids at the auction upon arrival to port). Transparent goby and crystal goby landings and fishing days (Fig 6.2.2) displayed very similar trends, with the exception of Aphia minuta in 2009-2010 to 2012-2013, and Crystallogobius linearis in 2005-2006. CPUE (kg/day per vessel) trend was also similar to that of landings (Fig. 6.2.3). In the case of transparent goby, the highest CPUE in 2010- 2011 was attained in a fishing season with relative low number of fishing days; and conversely, in Crystallogobius linearis, the highest landings and number of fishing days in 2003- 2004 resulted in a moderate CPUE.

4500 Aphia minuta 180 14000 350 4000 160 Cristallogobius linearis 12000 300 3500 140 10000 250 3000 120

2500 100 8000 200 days

days

kg kg 2000 80 6000 150 fising

1500 60 fishing 4000 100 1000 40 500 20 2000 50 0 0 0 0 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 Fig. 6.2.2. Landings (kg; in blue, left axis) and fishing days (in red, right axis) trend of transparent goby and crystal goby in the Catalan Coast over the fishing seasons 2001-2002 to 2012-2013.

4500 Aphia minuta 50 14000 Cristallogobius linearis 80 4000 45 12000 3500 40 60 35 10000 3000 30

8000 2500

kg 25 kg 40 2000 20 6000

1500 kg/day/vessel 15 4000 kg/day/vessel 20 1000 10 2000 500 5 0 0 0 0 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ 2002 ‐ 2003 ‐ 2004 ‐ 2005 ‐ 2006 ‐ 2007 ‐ 2008 ‐ 2009 ‐ 2010 ‐ 2011 ‐ 2012 ‐ 2013 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 Fig. 6.2.3. Landings (kg; in blue, left axis) and fishing season CPUE (kg/day per vessel; in red, right axis) trend of transparent goby and crystal goby in the Catalan Coast over the fishing seasons 2001-2002 to 2012-2013. Further information and analysis of transparent and crystal goby landings and CPUE is presented in section 2.5. The gobids fishery represents a small part of the overall boat seine fleet landings and activity (see for comparison Figs. 4.2.2 and 4.2.3 in Part I). It is worth mentioning, according to the historic data series (2000-2013), the very low importance of the Ferrer's goby (Pseudoaphia ferreri), both in terms of landings and in income from the sale at the auction. Information on the Ferrer's goby landings is recorded only for 2009 to 2012 ( Table 2.2.1).

Table 6.2.2. Pseudoaphia ferreri landings (kg) and income (euros) from the sale at the auction.

Pseudoaphia ferreri landings income (kg) (euros)

2009 273,9 774,5

2010 32,7 134,2

2011 34,9 211,1

2012 6,9 23,6

6.3 Fishing areas Fishing activity has been monitored through log books, from 16 December 2012 to 28 February 2013. Information is available, on a daily basis and by vessel and fishing operation, on the target species catches, coordinates and depth of the fishing ground and time at sea. The analysis of these data allowed evaluating the fishing effort, in terms of fishing days, number of hauls, hours at sea, and fishing ground. Vessels from two fishing ports, Barcelona and Blanes were devoted to gobids fishery. From Barcelona fleet one boat fished regularly during season whereas other one fished sporadically. The species caught was Aphia minuta at depths ranging from 8 m to 23.7 m (average 11.2 m). One boat from Blanes fleet fished regularly gobids and other one very sporadically. Target species for this fleet is Crystallogobius linearis caught at depths ranging 37 to 52 m (average 46.8 m). Data are available on a total of 33 daily trips and 106 hauls, carried out by the boat seine "sonsera" fleet with base in Barcelona. Fishing fleet of port of Blanes carried out 23 daily trips and 71 hauls. Fishing hours at sea showed a decreasing trend from December 2012 (6.36 hours in Barcelona and 7 hours in Blanes) to February (Figure 6.3.1).

Hours on the sea 7,2 7 6,8 6,6 6,4 Hours 6,2 6 5,8 5,6 December January February

Barcelona Blanes

Figure 6.3.1 Average of daily hours spends on the sea by month and fishing port.

The maps show the position of the hauls during the studied period (Figure 6.3.2). Aphia minuta was caught on the mouth of Llobregat River, showing the preference for fresh/brackish water of this species (Figure 6.3.3). Crystallogobius linearis was caught in an area south of Blanes port (Figure 6.3.4).

64 As shown by the maps, the "sonsera" is not used on sea bottoms characterized by the presence of sea grass meadows, in particular Posidonia oceanica. The fishing activity can have been carried out close to, but not directly on, Posidonia meadows

Figure 6.3.2 General map of two gobids fishing areas (Barcelona and Blanes). Round dots= fishing position from fishermen log book.Square dots = position of hauls with observer on board. Dark green spots Posidonia according 1992 survey; light green spot Posidonia according 2012 survey (only present in front of Mataro)

Figure 6.3.3 Detail of Aphia minuta fishing grounds

Figure 6.3.4 Detail of Crystallogobius linearis fishing grounds.

66 6.4 By-catch composition The analysis of the boat seine catch of transparent goby and crystal goby (or “llengüeta” in Catalan) developed during the scientific study has evidenced the importance of the echo-sounder for “sonsera being high selectivity. The presence of by-catch species can be detected by the echo-sounder during the fishing process, which results in selective landings without or with very few no-objective species. The by-catch composition from the fishing grounds where the “sonsera” boat seine fleet operates was studied by scientific cruises from December 2012 to May 2013. Samples were monthly obtained on board from two ports in the Catalan coast, Blanes in the north and Barcelona in the south. The objective species in the north is the crystal goby, Crystalogobius linearis, and in the south the transparent goby, Aphia minuta. Later, in the laboratory, species of by-catch were identified and length and weight were obtained for each specimen. The two llengüeta species are very small with a very low weight. Therefore, the weight ratio between these species and their by-catch is different from the sand eel case. In this case the study of the selectivity had only information from sampling on board and all by-catch species retained in the gear were analysed, that is, including the species that otherwise would have been returned at sea alive. There is no data on by-catch in the fishermen log-books. The analysis of percentage in weight of target versus non-target species defines the selectivity of this kind of fishery. It is important to notice that the by-catch species analysed would have been released at sea alive if it had not been studied (see video 55 and 66). Commercialization of by-catch was forbidden during the scientific study as in the case of sand eel. Transparent goby, Aphia minuta The by-catch percentage in weight in Aphia minuta catches is 29.28%, which represents 61kg of transparent goby against 17.86kg of by-catch. More than 20 species can be caught regularly throughout the study and, although the number of individuals is low, the percentage is always high due to relationship of weights. For instance: 3.2% of red mullet Mullus barbatus, 1.5% of common pandora Pagellus erythrinus and 2.6% of horse-mackerel Trachurus spp which represents 60, 11 and 49 individuals respectively. Juveniles of small pelagic such as european sardine Sardina pilchardus were present of 1.64% only in two hauls (one in March and another in April) over the complete study period. Minimum size The species more abundant and frequent and with a regulated minimum landing size were analysed and they length frequency distributed presented. Mullus barbatus appeared in December, February and March but did not present individuals under 11 cm. Individuals of < 12 cm of Diplodus annularis were present but only in one haul and representing no more than 3.3 % in weight. The small pelagic Sardina pilchardus evidenced individuals with a length frequency distribution of <11cm.

5 http://www.icm.csic.es/rec/lleonart/Videos/Vessel9.wmv 6 http://www.icm.csic.es/rec/lleonart/Videos/Vessel211.wmv

67 Mullus barbatus D. annularis 14 6

12 5 10 4 8 3 6 2 4 2 1

Number of of individuals Number 0 of individuals Number 0 123456789101112 5 7 9 11 13 15 17 TL cm TL cm

Sardina pilchardus 2000

1500

1000 March

500 April

Number of of individuals Number 0 33.544.55 TL cm

Figure 6.4.1. Length frequency distribution of Mullus barbatus, Diplodus annularis and Sardine pilchardus retained as by-catch of transparent goby.

Along the complete period of study only two individuals of Cephalopods has been captured, and in the case of Trachurus spp and Pagellus erythrinus only 10 and 8 individuals were fished. It is important to remark that the by-catch species analysed would have been released at sea alive if it had not been studied. Crystal goby, Crystalogobius linearis Crystallogobius linearis fishery behaves similarly to Aphia minuta, with a high number of by-catch species which, being heavier, show high weight percentages of the total catch. Throughout the study period 87.60kg of crystal goby against 139.95 kg of by-catch species were analyzed. Based on this relationship the percentage of most frequent species among all the by-catch is presented. The percentage in weight of red mullet, Mullus barbatus, common Pandora, Pagellus erythrinus and annular sea-bream was 11.7%, 35.3% and 21.8% respectively, and 488, 963 and 21 individuals respectively. Regarding cephalopods, Allotheuthis media, Octopus vulgaris and Loligo vulgaris, were represented with percentages of 6.5%, 5.1%, 5.7% respectively and 5 individuals each species. Pelagic species both adults and juveniles are practically absent over the complete study period (Spratus spratus, Alosa fallax and Sardina pilchardus of 0%; Sardinela aurita of 27.4% and 12 individuals) Minimum size Taking into account the species that have a legal minimum size, Pagellus erythrinus had been caught in an important number undersized (<15cm) individuals in January, representing 57% of the total individuals analysed. Mullus barbatus showed few individuals with sizes <11cm, representing 9% of the total individuals caught, and species of sparidae family, Boops boops (<11cm) and Diplodus vulgaris and D. annularis (<12cm) were practically inexistent with 2.3%, 0% and 1.3% respectively of the total individuals captured over the study (Figure 6.4.2).

68 As mentioned in the case of sand eel and transparent goby, these by-catch species, retained for analysis, would have been returned at sea alive. During the project it was prohibited the commercialization of by-catch

Pagellus erythrinus Mullus barbatus 80 50 70 40 60 50 30 40 Jan 20 Jan 30 Feb 20 Feb Mar 10 10 0 Number of of individuals Number 0 of individuals Number 9 10 11 12 13 14 15 16 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 9.5 10.5 11.5 12.5 13.5 14.5 15.5 16.5 TL cm TL cm

Boops boops Diplodus spp 35 16 30 14 12 25 10 20 Jan 8 15 D. vulgaris Feb 6 10 4 D. annularis March 5 2

0 of Number individuals 0

Number of of Number individuals 9 1011121314151617181920212223 9 1113151719212325 TL cm TL cm

Figure 6.4.2. Length frequency distribution of Pagellus erytrhinus, Mullus barbatus, Boops boops and two species of Diplodus from by-catch of crystal goby fishery.

In conclusion, similarly to what has been indicated for sand eel, it is important to note that the control measures to avoid the commercialization of by-catch and the good results regarding the selectivity and the success of the process to release alive to the sea the by-catch species, is very important to recommend to limit the by-catch species presence to a maximum weight percentage of 1% of the total catch or less than 5kg of total weight. Furthermore, by-catch species commercialization must remain forbidden.

6.5 Assessment Species In the study area the boat seine fleet targets two gobid species: transparent goby (Aphia minuta) and crystal goby (Crystallogobius linearis). Landings of a third gobid species, the Ferrer's goby (Pseudoaphia ferreri), are negligible (see Table 2.2.2). Data Historical Series The data source on landings and fishing effort is the same used in section 2.2. Data are presented at annual and monthly scales. The unit of effort considered is the number of fishing days (i.e. the sum of the number of days each boat seiner sold transparent goby or crystal goby at the auction upon arrival to port). Monthly catch per unit of effort (CPUE) was calculated as kg per day and vessel. Data are presented by fishing season i.e. from November to May.

69 Catch and CPUE Over the fishing seasons 2001- 2002 to 2012- 2013, landings of the two species displayed marked fluctuations, as shown in section 6.2 (Fig. 6.2.1). In the case of the transparent goby, the landings fluctuations were inter-seasonal, and ranged between 0.5 t in 2006- 2007 and 4 t in 2005- 2006. In crystal goby landings, though, two period are distinguished, from 2001- 2002 to 2005- 2006 fishing seasons, with landings > 5 t per season and a peak in 2003-2004 (12.4 t), and from 2006- 2007 onwards, with landings negligible. No explanation is available on whether the very low landings of crystal goby in this period are due to under-reporting or to a change in the fishermen's strategy. The monthly landings, fishing days and CPUE (kg/day per vessel) trends over 2001- 2002 to 2012 2013 are presented in Figs. 6.5.1 and 6.5.2, for transparent goby and crystal goby. These figure show and suggest a number of interesting questions regarding the boat seining gobids fishery, based on annual species with very short life cycle. i) In both species, highest landings did not occurred at the beginning of the fishing season, which suggest that the onset of the fishing season was not coincidental with the massive incorporation of recruits. In addition, the time when the peak of landings was attainted could change from one fishing season to the next one. In transparent goby, February was the month with more landings peaks, but these were also observed in November, December, March, even in April. In crystal goby, February was also the month with more landings peaks, but these were also observed December, January and March. ii) Generally, landings, fishing days and CPUE trends are quite similar, with some exceptions, such as the fishing seasons 2001- 2002, 2004- 2005, 2005- 2006, 2006- 2007 and 2009- 2010 in transparent goby. In 2004- 2005, by the end of the fishing season in April, the monthly CPUE in markedly increased regarding the previous month, which might suggest that the resource was still abundant. In the other aforementioned fishing seasons, the CPUE trend, with two peaks, increased after

70 60 1800 25 300 25 450 2005‐2006 2009‐2010 2001‐2002 400 1600 50 250 20 20 1400 days days

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15 15 150 300

200 10 monthly monthly

10 monthly 10 100 200 monthly monthly 100 monthly 5 5 50 5 100 0 0 0 0 0 0 111212345 111212345 111212345 month month month Fig. 6.5.1. Transparent goby (Aphia minuta). Monthly CPUE (kg/day per vessel; blue; left axis), fishing days (green; left axis), and landings (in kg; red; right axis). having decreased, suggesting the incorporation of new recruits as the fishing season advanced. In crystal goby, the high CPUE at the end of the fishing season (e.g. 2004- 2005, 2005-2006, 2006-2007, 2008- 2009, 2012- 2013) would suggest that the fishing season ended when the resource was still relatively abundant. In any case, landings from 2006- 2007 were very low. iii) The monthly trend of the transparent goby CPUE suggest that in the fishing seasons mentioned in i) two different cohorts might have been exploited along the fishing season (Fig. 6.5.3), since one monthly peak was followed by decreasing CPUE, and two or three months later, CPUE increased, this increase followed by decreasing CPUE. The Aphia minuta life cycle is short, usually lasting only one year and ends shortly after reproduction. The breeding season is quite long and spawning takes place at least twice during its short life span. The existence of two different annual cohorts has been

71 120 6000 20 250 90 2500 2005‐2006 2009‐2010 80 2001‐2002 18 100 5000 2000 16 200 days days

days

(kg) (kg) (kg) 14

60 80 4000 12 150 fishing 1500 fishing

fishing

/ 50 /

60 3000 10 landings landings landings

CPUE 8 100 CPUE

1000 CPUE

40 2000 30 6 montly monthly 20 monthly 500 20 1000 4 50 monthly monthly monthly 10 2 0 0 0 0 0 0 11 12 1 2 3 4 5 111212345 111212345 month month month

200 300 70 4500 2006‐2007 40 2010‐2011 1000 4000 180 900 60 2002‐2003 250 35 160 800 days days days 3500

30 (kg)

50 140 (kg)

(kg) 700

3000 200 120 25 fishing 600 fishing fishing

40 2500 / / /

100 150 20 500 landings landings

landings 30 2000 80 CPUE

CPUE 400 CPUE

15 1500 100 20 60 300 montly montly

10 monthly 1000 40 50 200 monthly monthly monthly 10 500 20 5 100 0 0 0 0 0 0 111212345 11 12 1 2 3 4 5 11 12 1 2 3 4 5 month month month

100 4500 40 800 10 80 90 2003‐2004 2007‐2008 4000 35 700 9 2011‐2012 70 80 8

days 3500 days days

30 600 60 (kg)

70 (kg) 7 3000 60 25 500 50 fishing

fishing 6 fishing

2500 / / /

50 20 400 5 40 landings

landings

2000 40 CPUE CPUE

CPUE 4

15 300 1500 30 30 3 montly 1000 monthly 10 200 20 20 2 monthly monthly 5 100 monthly 10 500 1 10 0 0 0 0 0 0 111212345 111212345 11 12 1 2 3 4 5 month month month

60 2004‐2005 2000 18 120 25 350 1800 16 2008‐2009 2012‐2013 50 100 300 1600 20 days

days 14 days

(kg) (kg) 250 1400 40 12 80 1200

fishing 15 fishing fishing

200

/ 10 / /

landings

30 1000 60 landings landings

8 800 150 CPUE CPUE

CPUE 10

20 600 6 40 100 monthly monthly 400 4 monthly 10 5 monthly 20 monthly monthly 50 200 2 0 0 0 0 0 0 11 12 1 2 3 4 5 111212345 111212345 month month month Fig. 6.5.2. Crystal goby (Crystallogobius linearis). Monthly CPUE (kg/day per vessel; blue; left axis), fishing days (green; left axis), and landings (in kg; red; right axis).

20 18 2001‐2002 2006‐2007 16 20 vessel)

14 18 per 16 vessel) 12 14 per 10

(kg/day 12

8 10 CPUE

(kg/day 8 6

6 4

CPUE 4 2 monthly 2 0 0

111212345 monthly 111212345 month month

2005‐2006 2009‐2010 50 16 45 14 40 vessel) vessel) 12 35 per per 30 10 25 8

(kg/day 20 (kg/day

6 15 4

CPUE 10 CPUE

5 2 0 0

monthly 111212345 monthly 111212345 month month Fig. 6.5.3. Transparent goby (Aphia minuta). Monthly CPUE (kg/day per vessel) trend in fishing seasons displaying more than one peak.

72 proposed (La Mesa et al 2005, and references therein). This hypothesis might explain the CPUEs and landings trend in some fishing seasons, as shown in Figs. 6.5.1 and 6.5.3. Stock- Recruitment relationship The available information does not allow exploring the stock- recruitment relationship, if any, neither in transparent goby nor on crystal goby. Biomass estimation. Depletion methods Depletion methods are based on the principle that a decrease in the CPUE as the population is reduced or depleted is directly related to the extent of population decrease. This is not the case in the boat seine gobids fishery and this is why this methodology has not been applied. As shown in Figs. 6.5.1 to 6.5.3, the highest CPUE are not obtained at the beginning of the fishing season, which suggest that the onset of the fishing season is not coincidental with the massive incorporation of recruits; the CPUE trend may display more than one peak along the fishing season; and, also, CPUE trend in the last months of the fishing season is increasing, suggesting increasing abundance by the end of the season. Conclusions of the assessment Transparent goby (Aphia minuta) and crystal gobly (Crystallogobius linearis) landings over the fishing seasons (from November to May) 2001-2003 to 2012- 2013 displayed marked fluctuations. In addition, the landings pattern within each fishing season was also very variable, the landings peak in each season may occur at different months. The monthly landings and CPUE's trend in some of the fishing seasons, which increased after decreasing, suggest the incorporation of new individuals once the fishing season has started, which prevents the use of depletion methods. The highest CPUE were not obtained at the beginning of the fishing season, which suggest that the onset of the fishing season is not coincidental with the massive incorporation of recruits. Historically a very limited number of boats targeted gobids (four to six). Since from now on, in case a management plan is implemented for boat seining, all boat seiners might go fishing gobids (although unlikely that this happen in the end), the use of a reference CPUE (daily catch per boat) threshold for the fishing season based on the activity of a very limited number of vessels would be meaningless. For this reason, 2001-2013 historical average catch is proposed as TAC, which provide an estimate of 1.8 tons of Aphia minuta and 3.8 tons of Crystallogobius linearis. In any case, it is the sand eel that drive the boat seining activity; both landings and fishing days resulting from targeting gobids are very low regarding those of sand eel.

7 CONCLUSIONS

1) In the Catalan coast, the boat seine fishery is driven by the Mediterranean sand eel (Gymnammodytes cicerelus), catches of smooth sand eel (Gynammodys semisquamatus) representing only around 2% of the total. Gobid species, transparent goby Aphia minuta and crystal goby Crystallogobius linearis, landings and activity of the boat seine fleet targeting these species are low in comparison to Mediterranean sand eel. 2) The boat seine fishing gear, locally called "sonsera", is used exclusively for fishing sand eel and gobid species. The sand eel fishing grounds are located very close to the

73 coast (depending on the zone, within 400- 600 m from the coast), in shallow waters (6- 16 m depth). Gobid species are fished in muddy or sandy-muddy bottoms, at 7- 12 m depths transparent goby in the southern fishing grounds, and at 30-50 m depth crystal goby in the northern fishing grounds. Impact on the environment 3) From plotting haul positions against phanerogams distribution maps, it can be concluded that the "sonsera" is not used on sea bottoms characterized by the presence of sea grass meadows, in particular Posidonia oceanica. 4) The analysis of the boat seine catch when targeting sand eel evidenced the high selectivity of the “sonsera”, as the presence of by-catch species can be detected by the echo-sounder, which allows performing selective fishing operations resulting in catches without or with very few non- target species. The percentage in weight of by- catch species regarding the total sand eel’s catch was very low over the study period, around 2-3%. 5) In the case of gobids fishery, the presence of by-catch species is also detected by echo-sounder to improve the selectivity of the “sonsera”. The two gobid species are very small with a very low weight. Therefore, the weight ratio between these species and the by-catch species presented a different picture from the one presented in the case of the sand eel. In Aphia minuta catches represented 61kg of transparent goby against 17.86kg of by-catch species, and for Crystalogobius linearis the relationship was 87.60kg of crystal goby against 139.95 kg of by-catch. It is important to notice that the by-catch species analysed would have been released at sea alive if they had not been retained for study. Commercialization of by-catch species was forbidden during the scientific study as in the case of sand eel. 6) Taking into consideration the control measures to avoid the commercialization of by- catch species, the good results regarding the gear selectivity the release alive into the sea of the by-catch species, it is recommended to limit the by-catch species presence to a maximum weight percentage of 1% of the total catch or less than 5kg of total weight. Furthermore, by-catch species commercialization must remain forbidden. Sand eel fishery 7) This study has allowed knowing the main biological traits of Mediterranean sand eel (distribution, growth, reproduction period, size-at-first maturity, timing of recruitment). The biology of G. cicerelus and G. semisquamatus in the study area were unknown, excepting scattered information reporting the presence of larvae at certain time of the year. 8) According to the assessment scenarios considered it appears that the sand eel fishery of the two half periods (2012-2013) is quite healthy. In the worst parameter combination a slight growth overfishing could appear. However no traces of recruitment overfishing have been detected. 9) It is advisable to maintain the fishing limitations applied during the study, for which an effort reduction to a half and a TAC was established. Furthermore monthly harvest control rules to keep the fishery under continuous observation is highly recommended. 10) In 2013, the boat seiners did not encounter problems to attain the monthly quotes fixed to reach 819 t by the end of the fishing season, which would suggest that sand eel abundance did not decrease in relation to 2012. A quota for 2014 of 819 t is proposed,

74 the same quota as in 2012 and 2013. In case a plan for the management of the sand eel fishery is approved, in the coming years, the fishing season quota will be fixed at the start of the season, based on the results of the previous fishing season. 11) Gimnammodytes cicerelus reproduction period in the area extends from November to February and at the end of the fishing season in mid- December the population consists of individuals that have attaint the size-at-first-maturity. Therefore, it is advisable to maintain the timing of the currently implemented closed season, from mid- December to the end of February. 12) Since the yield at the start of the fishing season has been shown to be related to the yield at the end of the previous fishing season (SSB-Recruitment relationship), it is advisable not to modify the current closed- season period, from 16 December to the end of February. Gobids fishery 13) Transparent goby (Aphia minuta) and crystal gobly (Crystallogobius linearis) landings over the fishing seasons (from November to May) 2001-2003 to 2012- 2013 displayed marked fluctuations. In addition, the landings pattern within each fishing season was also very variable, the landings peak in each season may occur at different months. The monthly landings and CPUE's trend in some of the fishing seasons, which increased after decreasing, suggest the incorporation of new individuals once the fishing season has started, which prevents the use of depletion methods. Available data do not allow performing reliable LCA assessments. 14) The highest CPUE were not obtained at the beginning of the fishing season, which suggest that the onset of the fishing season is not coincidental with the massive incorporation of recruits. 15) Historically a very limited number of boats targeted gobids (four to six). Since from now on, in case a management plan is implemented for boat seining, all boat seiners might go fishing gobids (although unlikely that this happen in the end), the use of a reference CPUE (daily catch per boat) threshold for the fishing season based on the activity of a very limited number of vessels would be meaningless. For this reason, 2001-2013 historical average catch is proposed as TAC, which provide an estimate of 1.8 tons of Aphia minuta and 3.8 tons of Crystallogobius linearis.

75 8 REFERENCES

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