Report of Japan s scientific observer program for tuna longline fishery in the Atlantic Ocean in the fishing year of 2007

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1 SCRS/8/177 Report of Japan s scientific observer program for tuna longline fishery in the Atlantic Ocean in the fishing year of 7 Yasuko Semba, Takayuki Matsumoto, Hiroaki Okamoto and Toshiyuki Tanabe National Research Institute of Far Seas Fisheries, Fisheries Research Agency, Orido, Shimizu-ku, Shizuoka City, Shizuoka Prefecture, Japan Summary This document summarizes the data collected in the Japanese scientific observer program for longline fishery in the Atlantic Ocean conducted from September 7 to February 8. In 7 fishing year (FY), eight trips ( operations and 1,1,17 were observed. Majority of observation was conducted in the North Atlantic. Number of observed species and individuals were 59 and 1,81, respectively. In the North Atlantic, blue shark was the most dominant and tuna species (mainly albacore and bluefin tuna) followed after blue shark. Except for blue shark, Atlantic, albacore was the most dominant species in the central north Atlantic, while bluefin tuna was the most dominant in eastern and western north Atlantic. In general, more species were observed in southern ( and tropical ) than northern (off Ireland, central north Atlantic, Grand ). Survival rates (percentage of the species caught alive) of catches were usually high for sharks, moderate for tunas and relatively low for some billfish. It was relatively higher in northern s and lower in southern s. Regional difference in sex ratio was observed for many species. s were dominant in southern s and males were dominant in northern s for most of species. Length frequency distribution showed that large individuals were more frequently seen in southern s for many species such as bluefin tuna, bigeye tuna, yellowfin tuna and blue shark. Keywords Long lining, Tuna fisheries, Bycatch, Catch composition, Size composition, Sex ratio Introduction Fisheries Research Agency of Japan has conducted its national scientific observer programs for Atlantic tuna longline vessels since the mid 199s in collaboration with Fisheries Agency of Japan. Data collection includes vessel attributes, gear configuration, species identification, biological sampling and various measurements on all catches. This observer program was first conducted in response to the recommendation made by ICCAT for tropical tuna in 1996 and the other relevant recommendations. Two to nine trips have been monitored annually. Previous results until 6

2 fishing year (FY) 1 were reported to the SCRS meetings (ex. Semba et al. 7, Matsumoto 6). This document provides the information on the level of Japan s observer program and the summary of results including data collection in Japan s national scientific observer program conducted in 7 FY. Outline of the observer program Eight observers were trained and sent to the Japanese commercial tuna longline vessels operating in the Atlantic. The observer training program includes keys for species identification, data recording protocols for information on fishing operation and catches, and protocols for taking various measurements for catches. Fishing activities, oceanographic and weather condition, gear configuration, bait and observed hook number were recorded. Size measurements were conducted for all of the catches taken up on the deck, which includes various length and weight data such as body length, whole weight and/or processed weight, clasper length, gonad weight. In addition, time when a catch was retrieved, the branch line number on which the catch was hooked, the life status of the catch (alive or dead), sex, wound status and maturity index were recorded as much as possible. Some biological sampling was also conducted for stomach contents, muscle, and genital gland. Pop-up archival tag was attached to one bluefin tuna and then released. Species identification and Measurements i) Identification of species and related information All of the catches taken on the deck were identified by species and recorded, and the catches which were not hauled up on the deck were also recorded. According to the 7 National Report of Japan (FAJ and FRA 7), 7 program covered about five percent (.6%) of the total number of fishing vessels operating in the entire Atlantic Ocean from January to December in 7. Each catch was identified for life status immediately after it was hauled on the deck or when they were released at the deck side. The status alive was further separated into no details, vigorous, sluggish or injured. ii) Measurement of catch Length was measured for all intact catches by 1cm interval (round up) and the following measurements were applied for different fish groups; fork length for tunas, post-orbit fork length (POFL) for billfishes, precaudal length for sharks, disk length for rays, total or fork length for other teleosts. Length was measured with a caliper. Whole body weight (to the nearest.1kg in principal), processed weight (to the nearest 1 kg) and gonad weight (for tunas and billfishes; to the nearest.1kg) were measured as much as possible. 1 Fishing year is defined as August to July.

3 When there were substantial numbers of catch, priority was given to tunas and billfishes but the number of catch was counted for all species. Clasper inner length (between the anterior margin of the cloaca and the posterior clasper tip) was measured and recorded for male sharks by.1 cm interval. iii) Sex determination and status of maturity Sex determination was conducted through the observation of genital gland for teleosts and with or without of clasper for sharks and rays. The status of maturity of ovaries for tunas and billfishes was identified on megascopic basis and divided into the following categories. M1: Ovary is small and no grains of egg are visible. M: Ovary is larger than M1 and small grains of egg are visible. Arteries are developed on the surface of ovary. M3: Each grain of egg is over.-.5mm and ovary is full of them. The color of egg is light pink and no translucent egg is observed. Arteries are well developed. M: Ovary is very large and some translucent eggs are observed which are easy to come off. M5: Many eggs are exfoliated in the ovary and are about to get out of. M6: Ovary is comparatively large but it has a open cavity inside. As for sharks, maturity was checked by the existence of sperm and embryos for males and females, respectively. iv) Archival pop-up tagging for bluefin tuna Archival pop-up tagging was conducted for one bluefin tuna in the north eastern Atlantic to investigate the vertical and horizontal swimming behavior. The Pop-up Archival Tag (PAT: Microwave Telemetry Inc., PTT-1) was set to collect data of light intensity, depth and water temperature, and programmed to be popped-off six months after the release. PAT was attached to fish by harpooning from the side of vessel while keeping the fish in the sea surface, trying to tag at the dorsal muscle under the first dorsal fin, and then released by cutting the line. Length and weight of the fish were estimated by eye measurement of the observer or fishing master. Summary Results i) Trip and of operation Eight trips were made in 7 FY. Table 1 shows the detailed information for each trip and observed effort. Total of operations were observed in eight tips in 7 FY (average: 53 per trip). Total

4 number of observed hook was 1,1,17(average: 16,5. The of operation was shown in Figure 1. Fishing was divided into five s; 1 (), (Grand ), 3 (Central North Atlantic: indicated as CNA thereafter), (off Ireland), 5 (Gulf of Guinea, off Dakar: indicated as tropical thereafter). In 7 FY, four vessels operated in the. Another three vessels operated in subarctic higher than degrees north, one of which operated across the Atlantic Ocean, in the Grand, CNA, off Ireland (AT7). Only one vessel operated in the tropical (AT77). In summary, most observations were conducted in the temperate and subarctic. ii) Catch by species The list of species caught was shown in Table. The species whose observed number was less than 5 individuals were aggregated into others. Total of 59 species (including 3 unidentified species) with 1,81 individuals were recorded. Figure shows species composition in number by. Some observers reported shortbill spearfish, which is not known to distribute in the Atlantic. This was probably caused by the misidentification of white marlin or longbill spearfish or hatchet marlin. However, detailed information is not available. Therefore, we treated these fishes as Tetrapturus sp. and removed from further analysis. In the off Ireland, blue shark accounted for over 7% of total catch in terms of number of fish, and followed by bluefin tuna (17%) and albacore (6%). This trend was similar to the past report (Semba et al. 7). In the CNA, blue shark and albacore dominated and these species comprised 88% of total catches. Compared to the off Ireland, the percentage of blue shark decreased (5%) and that of albacore increased (%). In the Grand, blue shark was the most dominant species (9%) in the catch. Except for blue shark, tuna species (albacore, bluefin tuna, bigeye tuna and yellowfin tuna) accounted for 5% of all catches. Among tuna catch, bluefin tuna was the most common (6 % of tuna catch, 7% of total catch), followed by albacore (11%) and bigeye tuna (8%). In the, tuna species accounted for 5% of all catch and albacore was the most common species (3% of total catch and 6% of tuna group catch). Billfish accounted for 5 % of total catch, which was the highest among all s. The percentage of shark was smaller than 1% and blue shark comprised only 6% of total catch. In the tropical (Gulf of Guinea and off Dakar), bigeye tuna dominated in the catch (5%). The number of species observed was the largest among the all s, while the total observed number of individuals was relatively small compared to other s. The number of fish measured and sampled was indicated for each item in Table 3.

5 iii) CPUE for major species Nominal CPUE (catch number per 1 for major species by was calculated (Figure 3). The observed hook number was used as fishing effort for calculation of CPUE. Tunas CPUE of albacore was the highest in the CNA followed by the. For bluefin tuna, CPUE was the highest in the Grand and very low in the other northern s. For tropical tuna, CPUE of bigeye tuna was the highest in the tropical while that of yellowfin was the highest in the. Billfishes Swordfish CPUE was the highest in the tropical and CPUE decreased as the latitude becomes higher. Atlantic blue marlin was only recorded in the and the tropical. The regional trend of CPUE for white marlin and Atlantic sailfish showed opposite trend; the former CPUE was higher in the than in the tropical while the latter was higher in the tropical than in the. Longbill spearfish were only caught in the. Sharks and ray Blue shark had the highest CPUE in the CNA. Including the CNA, CPUE in the northern was relatively high, while that in the southern was relatively low. Porbeagle was only caught in the CNA and the Grand. On the other hand, CPUE of shortfin mako was the highest in the Grand and moderate in other s. Bigeye thresher was only abundant in the tropical and oceanic whitetip shark was caught in s except for the CNA and the off Ireland. Tiger shark and stingray were the most abundant in the and secondary most abundant in the tropical. iv) Life status of catch The survival rate (1* sum of alive individual / sum of [alive+dead+unknown] individuals: SR) was shown in Table. The species whose observed number was less than 5 individuals were excluded from consideration. Additional survival rate was calculated based on total number without individuals of unknown status, which was presented in the Table in parenthesis for corresponding species. Tunas For albacore, survival rate (SR) ranged from 3 to 69 %, which was similar to that of bluefin tuna (1 to 68%). Regional trend that SR was high in the northern and low in the temperate was observed for these two species except albacore in the CNA (SR: 3%). For albacore, SR was over 6% in the off Ireland and the Grand and lower than 5% in the and CNA. For bluefin tuna, SR was almost over 5% in the Grand, CNA and off Ireland, but around % in the. For bigeye tuna, SR in the temperate (over 7%) was higher

6 than the tropical (9%). This trend was observed for yellowfin tuna (: 6%, tropical : 5%), too. Billfishes For swordfish, regional differences in SR were observed with no latitudinal trend. Its SR was relatively high in the off Ireland and moderate in the CNA, the Grand and the tropical and low in the. Atlantic blue marlin, white marlin, Atlantic sailfish and longbill spearfish had the same trend that SR in the was much higher than that in the tropical. Sharks and ray For blue shark, SR in subarctic s was around 9% except off Ireland (9%), which has nearly 1 % SR if unknown data was removed from the total number. SR in the tropical for blue shark (79%) was smaller than value of the temperate and subarctic s. For shortfin mako, there was no marked regional difference and SR was around 7% in all s. For bigeye thresher, SR in the tropical (71%) was higher than that in the (6%). SR of tiger shark and silky shark (the ) and crocodile shark (the tropical ) was 1%. For stingray, SR was relatively high (> 9%) in both Florida and the tropical. v) Sex ratio Sex ratio (1*number of male / number of male and female) was calculated (Table 5). The species which observed number was less than 5 individuals was excluded from consideration. Tunas For albacore, male was dominant especially in the, the CNA (>7%) compared to the off Ireland (56%). For bluefin tuna, the ratio of male was higher than that of female in many s. For bigeye tuna, male was dominant in the and the tropical, but sex ratio was even in the Grand. For yellowfin tuna, male was dominant in the tropical but sex ratio was even in the. Billfishes For swordfish, female was dominant in the and the tropical. In the CNA, sex ratio was nearly even. For Atlantic blue marlin, male dominated, while sex ratio strongly biased to female in the tropical. For white marlin, sex ratio was even in both s off Florida and the tropical. For Atlantic sailfish, sex ratio was nearly even in the, while all individuals were female in the tropical. For longbill spearfish, sex ratio biased to female in both s for and the tropical, especially in the tropical. Sharks and ray For blue shark, female dominated in the off Ireland, the CNA, the Grand and the tropical, while male dominated in the. For shortfin mako shark, male was

7 dominant in all s, especially in the CNA. The degree of male dominance for shortfin mako decreased from 91% in the CNA, 75% in the off Ireland, 6% in the tropical, 59% in the, 55% in the Grand. For tiger shark () and bigeye thresher shark (tropical ), sex ratio biased to female, especially for bigeye thresher shark. For crocodile shark and stingray, sex ratio was nearly even in the tropical. vi) Length of the fish caught Length frequency distributions of major tuna species, billfishes and sharks were shown in Figure. Tunas For albacore, regional difference in length frequency was observed. Fish between 7 to 9 cm (Juvenile) dominated in the Grand, where average and median length are 8cm and 78cm, respectively. Off Ireland, the percentage of adult fish (larger than 9 cm: 5% maturity size) was higher than in the Grand, although there was a mode in the similar range (between 7 and 8cm) in both of these s. In the CNA and, adult had higher percentage than former two s. For bluefin tuna, regional difference in length frequency was also observed. Given that maturity size of western stock is 19cm, juvenile fish dominated in the Grand, while most of catches were made up of adult fish in the with the largest average length (1cm) and median length (7cm) among all s. In the s of CNA and off Ireland, the majority of the catches were individuals larger than 13cm (1% maturity size in eastern Atlantic). For bigeye tuna, regional difference between s of the temperate and the tropical was observed. In the s off Florida and Grand, fish were smaller than in the tropical and there was a marked mode at around 1cm in the former two s, while the additional mode was seen at around 135 cm in the Grand. The average (11cm) and median (11cm) in the was similar to those in the Grand (average: 115cm, median: 116cm), while size range was wider in the Florida than in the Grand. Given that maturity size of bigeye tuna is around 1cm (FL), adult occupied high percentage in the tropical. For yellowfin tuna, adult was common in both s of the and the tropical, given that maturity size of yellowfin tuna is around 1cm (FL). The length frequency in these two s showed bimodal shape and modes lied in around 1cm and 13-1cm, respectively. The average and median length in the tropical were 137cm and 1cm, respectively, which were larger than those in the (average: 15cm, median: 19cm). Billfishes For swordfish, due to a small number of observations, only s and the tropical were compared. The length range in the tropical (6-57 cm) was wider than that in the off Florida (68-37cm). The ratio of small individuals (< 9cm) in the tropical was much higher than that in the. The average and median length in the was 1cm. Considering that the maturity size of male and female is around 15cm (POFL), more than half of

8 catches were juvenile or subadult. In the tropical, length frequency distribution showed bimodal shape with two modes around 8-9cm and 16cm. In this, the proportions of adult and female individual were higher than those in the. For other billfishes, length data were only available from two s ( and tropical ), and the recorded catches were very few for tropical in many species. Because of this, it is difficult to compare length distributions by for most billfish. Comparable data was only obtained for Atlantic sailfish. For this species, some regional difference was observed between the and the tropical. Individuals caught in the tropical were much larger and female dominated compared to those caught in the. Sharks For blue shark, adult dominated in the and the tropical, where the majority of catch was larger than their maturity size (male 16cm, female 165cm by Pratt 1979). In these s, mature male dominated while mature female dominated in other s except for the Grand. Average and median length for the Florida were 199cm and 3cm, and those for the tropical were 18cm and 18cm. In the Grand, the percentage of subadult became higher than off Florida and the tropical, with average and median length of 151 cm and 15 cm, respectively. In this, male dominated as shown in the. In the CNA and the off Ireland, the juvenile occupied about 8% of total catch. Average and median length for the CNA were 15cm and 16cm, and those for Ireland were 135cm and 13cm. Generally, as latitude becomes lower, the percentage of mature individual increased. For shortfin mako shark, few data was obtained except the. Though conclusive description is difficult, juvenile and subadult were major components in catches in most of s. The catches of mature female were few in all s. vii) Pop-up archival tagging for bluefin tuna On 9 th September 7, one pop-up archival tag was attached to a bluefin tuna (16cm FL) and released in the northeastern Atlantic (8-16N, 11-5W). This tag was set to pop off 6 months after the release and actually popped off on 9 th March 8 as programmed. This individual made a trans-atlantic migration from the east to the west in the North Atlantic during 6 months at liberty. Detailed information will be presented in another document. Acknowledgement We greatly appreciate all observers for their hard work in order to collect valuable data and samples on the Japanese longline boats. Also, we would like to express special thanks to all the crews as well for their cooperation and understanding to the need for this program. Susumu Endo (OFCA) and Yozo Kobayashi (Japan Fisheries Resource Conservation Association) coordinated observer trip and preparation of material for research. Staffs of the Japan Tuna Fishermen s

9 Cooperative Association also helped in selecting the commercial vessels to be observed and coordinated the logistics in getting on board of these vessels. Reference Matsumoto, T. 6. Report of observer program for Japanese tuna longline fishery in the Atlantic Ocean from August to January 5. Col. Vo. Sci. Pap. ICCAT, 59(): National Research Institute of Far Seas Fisheries (6): NATIONAL REPORT OF JAPAN Pratt, H. W. Jr Reproduction in the blue shark, Prionace glauca. Fish. Bull., 77(): 5-7. Semba, Y., T. Matsumoto, H. Okamoto, and T. Tanabe. 7. Report of Japan s scientific observer program for tuna longline fishery in the Atlantic Ocean in the fishing year of 7. Co. Vo. Sci. Pap. ICCAT, SCRS/7/153

10 Table 1 Information on the trip of the scientific observer for Japanese tuna longline in the Atlantic during 7 FY. Trip ID AT71 AT7 AT73 AT7 AT75 AT76 AT77 AT78 off Ireland Grand Gulf of Guinea off Ireland C N A C N A off Dakar Grand range of latitude N.-59.8N N N N N 8.S-11.1 N N range of longitude W W W W W W W W Total Start date of operation 7/1/6 7/11/8 7/1/3 7/1/3 7/1/5 7/1/3 7/1/9 7/9/11 End date of operation 8/1/7 8/1/15 8//5 8//6 8//9 8//5 8//1 7/11/1 Number of operation Number of hooks observed 13,65 15, ,51 11,65 163,3 59, 97,1 8,1 1,1,17

11 Table The list of catch by fish species The species which observed total number is less than 5 individuals was aggregated. 7 Common name Scieintific name C N A Grand off Ireland Total Albacore Thunnus alalunga 1, ,83 Bluefin tuna Thunnus thynnus ,35 Bigeye tuna Thunnus obesus Yellowfin tuna Thunnus albacares Atlantic blue marlin Makaira nigricans White marlin Tetrapturus albidus Swordfish Xiphias gladius Atlantic sailfish Istiophorus albicans Longbill spearfish Tetrapturus pfluegeri Tetrapturus sp Pomfrets Bramidae Dolphin Coryphaena hippurus Ocean sunfish Mola mola Opah Lampris guttatus Wahoo Acanthocybium solandri Escoler Lepidocybium flavobrunneum Oilfish Ruvettus pretiosus Longnose lancetfish Alepisaurus ferox Lancetfishes Alepisaurus spp Ribbonfishes Trachipteridae Other teleost Unidentified fishes Blue shark Prionace glauca , ,63 Porbeagle Lamna nasus Shortfin mako Isurus oxyrinchus Crocodile shark Pseudocarcharias kamoharai Bigeye thresher Alopias superciliosus Tiger shark Galeocerdo cuvieri Oceanic whitetip shark Carcharhinus longimanus Silky shark Carcharhinus falciformis Other shark Unidentified thresher shark Alopiidae Unidentified requiem shark Carcharhinidae Unidentified hammerhead shark Sphyrnidae Sting ray Dasyatis violacea Other ray Total 5,5 1, ,86 1,587 1,81

12 Table 3 The number of individuals measured and sampled for main species. 7 Species Length Product weight whole weight Number of fish observed/measured Biological sampling Sex Branch line number Alive or not Maturity Albacore,718, , Bluefin tuna 1, 1, , Bigeye tuna Yellowfin tuna Atlantic blue marlin White marlin Swordfish Atlantic sailfish Longbill spearfish Tetrapturus sp Other telepst Blue shark,785, , Porbeagle Shortfin mako Crocodile shark Bigeye thresher Tiger shark Oceanic whitetip shark Silky shark Othe shark Sting ray Other ray Gonad weight Clasper length Stomach contents Muscle Gonad Total 1,169 9,1 1,1 6,978 3,817 1,1 79 1,

13 Table Life status of fish caught (7 FY) Percentage of alive which was calculated without unknown individual was presented in parenthesis. The species which observed total number is less than 5 individuals was excluded. Grand C N A off Ireland Alive Total number Percentage Species Dead Total No details Vigorous Sluggish Injured alive alive Albacore (1) Bluefin tuna (1) Swordfish (1) Blue shark (99.8) Shortfin mako (1) Albacore Bluefin tuna Swordfish Blue shark Shortfin mako Albacore Bluefin tuna Bigeye tuna Swordfish Blue shark Shortfin mako Albacore Bluefin tuna Bigeye tuna Yellowfin tuna Atlantic blue marlin White marlin Swordfish (33) Atlantic sailfish Longbill spearfish Blue shark Shortfin mako (75) Tiger shark Oceanic whitetip shark Silky shark Bigeye thresher Sting ray (1) Bigeye tuna Yellowfin tuna Atlantic blue marlin White marlin Swordfish Atlantic sailfish Longbill spearfish Blue shark Shortfin mako Crocodile shark Bigeye thresher Sting ray

14 Table 5 Sex ratio for major species by (7 FY) The species which observed total number is less than 5 individuals was excluded. Species Indeterminate Total Sex ratio off Ireland C N A Grand Albacore Bluefin tuna Blue shark Shortfin mako Albacore Bluefin tuna Swordfish Blue shark Porbeagle Shortfin mako Bluefin tuna Bigeye tuna Blue shark Shortfin mako Albacore Bluefin tuna Bigeye tuna Yellowfin tuna Atlantic blue marlin White marlin Swordfish Atlantic sailfish Longbill spearfish Blue shark Shortfin mako Tiger shark Bigeye tuna Yellowfin tuna Atlantic blue marlin White marlin Swordfish Atlantic sailfish Longbill spearfish Blue shark Shortfin mako Crocodile shark Bigeye thresher Sting ray

15 3 1 5 < division> 1: : Grand 3: Central North Atlantic (CNA) : off Ireland 5: Gulf of Guinea, off Dakar (tropical ) Figure 1 Operation for 7 cruise.

16 off Ireland C N A Grand Albacore Bluefin tuna Yellowfin tuna Bigeye tuna Atlantic blue marlin Swordfish Other billfish Blue shark Shortfin mako Other shark Sting ray Other teleosts % % % 6% 8% 1% Percentage (%) Figure Catch compositions for major species by.

17 Albacore Swordfish CPUE (no. per CPUE (no. per Bluefin tuna Atlantic blue marlin CPUE (no. per CPUE (no. per Bigeye tuna White marlin CPUE (no. per CPUE (no. per Yellowfin tuna Atlantic sailfish CPUE (no. per CPUE (no. per Longbill spearfish CPUE (no. per Figure 3 CPUE for major species.

18 Blue shark Bigeye thresher CPUE (no. per CPUE (no. per Porbeagle Oceanic whitetip shark CPUE (no. per CPUE (no. per Shortfin mako Tiger shark CPUE (no. per CPUE (no. per Stingray CPUE (no. per Figure3 (Continued.)

19 Albacore (off Ireland) Fork length (cm) Bluefin tuna (off Ireland) Fork length (cm) Albacore (CNA) 1 Bluefin tuna (CNA) Fork length (cm) Fork length (cm) Albacore (Grand ) Fork length (cm) Bluefin tuna (Grand ) Fork length (cm) Albacore () Fork length (cm) Bluefin tuna () Fork length (cm) Figure Length frequencies for major species.

20 Bigeye tuna (Grand ) male Yellowfin tuna () Fork length(cm) Fork length (cm) Bigeye tuna () Fork length(cm) male Yellowfin tuna ( ) Fork length (cm) Bigeye tuna ( ) Fork length(cm) male Figure (continued).

21 5 3 1 Swordfish (CNA) Atlantic blue marlin () Post-orbit fork length (cm) Post-orbit fork length (cm) 3 1 Swordfish (Grand ) Atlantic blue marlin ( ) Post-orbit fork length (cm) Post-orbit fork length (cm) 5 Swordfish () Post-orbit fork length (cm) 15 Swordfish ( ) Post-orbit fork length (cm) Figure (continued).

22 White marlin () Post-orbit fork length (cm) Atlantic sailfish () Post-orbit fork length (cm) 5 3 White marlin ( ) Atlantic sailfish ( ) Post-orbit fork length (cm) Post-orbit fork length (cm) Figure (continued).

23 Longbill spearfish () Orbital fork length (cm) Blue shark (off Ireland) Precaudal lenth (cm) Longbill spearfish ( ) Orbital fork length (cm) Blue shark (CNA) Precaudal lenth (cm) Blue shark (Grand ) Precaudal lenth (cm) Blue shark () Precaudal lenth (cm) Blue shark ( ) Precaudal lenth (cm) Figure (continued).

24 Shortfin mako shark (off Ireland) Precaudal length (cm) Shortfin mako shark (CNA) Precaudal length (cm) Shortfin mako shark (Grand ) Precaudal length (cm) 1 Shortfin mako shark () Precaudal length (cm) Shortfin mako shark ( ) Precaudal length (cm) Figure (continued).