FISHERIES SCIENCE 2000; 66: 812–825 Original Article Reproduction and food habits of two species of sawtail catsharks, Galeus eastmani and G. nipponensis, in Suruga Bay, Japan Taku HORIE AND Sho TANAKA* School of Marine Science and Technology, Tokai University, Shimizu, Shizuoka 424-8610, Japan SUMMARY: This study provides information on reproduction and food habits of Galeus eastmani and G. nipponensis in the east and west of Suruga Bay. A total of 731 G. eastmani and 754 G. nipponensis were sampled by commercial bottom trawlers in 1981–1989 and 1992–1996. Size at sexual maturity of both species of Galeus differed between the former and latter period. In G. eastmani, maturity size of females from the east tended to be smaller than those from the west. Both species laid large yolky ova the year round. Both species preyed on a wide variety of marine organisms, mainly Osteichthyes, Cephalopoda and Crustacea. Foods of G. eastmani differed between the east and west by season. Foods in the young stage of G. nipponensis differed from those of immature and mature by season. Body size of the young G. nipponensis was similar for mature G. eastmani, however the young fed on different organisms from G. eastmani in the east. Both species were voracious and opportunistic feeders. KEY WORDS: food habits, Galeus eastmani, Galeus nipponensis, reproduction, Suruga Bay. INTRODUCTION The sawtail catsharks belonging to the genus Galeus consist of four species around Japan, G. eastmani, G. sauteri, G. nipponensis, and G. longirostris. These four species inhabit the upper continental slope off Japan and are caught incidentally with commercial trawl and bottom long-line fisheries. In Suruga Bay, G. eastmani and G. nipponensis are often caught with bottom trawlnet together with other elasmobranchs, Cephaloscyllium umbratile, Etmopterus brachyurus and E. molleri etc. However, they are usually discarded. In Japan, only a few studies have been conducted on scyliorhinid sharks, including species of Galeus, despite there being 17 species, which makes the group the third most numerous among Japanese shark families. These studies have been on their taxonomy,1–3 reproduction4–6 and food habits.6 Biological information on both species of Galeus is merely limited to classification.1,7,8 The reproductive mode of both species is oviparity, and their *Corresponding author: Tel: 81-0543-34-0411. Fax: 81-0543-370239. Email: sho@scc.u-tokai.ac.jp Received 1 July 1999. Accepted 17 April 2000. reproductive cycle is unknown. There have not been specific studies on their reproduction or food habits. Thus, the influence the Galeus species may have on other aquatic organisms in bottom communities is unknown. It is important to evaluate their interrelationships with other aquatic organisms. This study provides the first detailed information on the reproduction and food habits of G. eastmani and G. nipponensis in Suruga Bay. MATERIALS AND METHODS A total of 731 (578 female and 153 male) G. eastmani and 754 (374 female and 380 male) G. nipponensis were sampled by commercial bottom trawlers in Heda port in western Izu Peninsula between April 1981 and May 1996 (Table 1), with the exception of 1990 and 1991 which could not be sampled between June and August because of seasonal closure for the trawl fishery. Seasons were divided into: (i) autumn (between September and November); (ii) winter (between December and February); and (iii) spring (between March and May). Fishing operation usually included six tows per day. For each, the fishing location and depth were recorded. Reproduction and food habits of sawtail catsharks FISHERIES SCIENCE 813 Table 1 Number of specimens in Galeus eastmani and G. nipponensis examined in this study Month September October November December January February March April May Total G. eastmani Female Male East West East West G. nipponensis Female Male 16 96 23 13 16 8 27 34 53 0 63 3 10 0 36 5 151 24 5 15 4 1 2 0 4 8 30 0 34 0 2 0 4 0 37 7 19 74 50 30 42 12 37 53 57 19 88 31 16 40 34 48 45 59 286 292 69 84 374 380 The specimens were fixed with 10% formalin after measuring total length (TL, mm) and bodyweight (BW, g) in the laboratory. After the fixation, the gonad weight, ovum diameter (OD), ovum weight, maximum width of shell gland, clasper length and stomach contents weight (SCW) were measured, and calcification of the clasper was observed. Sexual maturity of females was assessed using the following criteria, based on the examination of numerous specimens: (1) Immature. Ovary is thin and has no yolky ova. Ovum diameter is less than 5 mm in G. eastmani and 8 mm in G. nipponensis. The shell gland is small. (2) Mature. Ovary has large yolky ova. The shell gland is well developed. The maximum width of shell gland is greater than 10 mm in G. eastmani and 14 mm in G. nipponensis. Sexual maturity for males was assessed using the following criteria: (1) Immature. The claspers are short, soft and not calcified. (2) Mature. Stem cartilage of the claspers becomes hard or calcified. The research period of 1981–1996 was separated into two periods to determine any change of size at sexual maturity owing to the long period. The former period is 1981–1989 and the latter is 1992–1996. Stomach contents were examined in detail on the specimens caught after 1993. Food items were identified to the lowest taxonomic level possible, and their number and weight were recorded. Index of stomach fullness (ISF) was obtained by using the following formula: ISF = (SCW/BW) ¥ 100. Ranking index (RI) of stomach contents was obtained from the following formula:9 RI = %F ¥ %W (%F: percentage by frequency; %W; percentage by weight). For immature G. nipponensis, individuals under 430 mm TL were defined as the young stage for the com- Fig. 1 Map showing sampling area (shaded) of Galeus eastmani and G. nipponensis in Suruga Bay, Japan. parison of food habits by similar size on G. eastmani, because the maximum size of G. eastmani in the east was 430 mm TL. RESULTS Catch condition Fishing occurred between 90 and 450 m on the east side and from 52 to 405 m in depth on the west side of Suruga Bay, which are separated by Suruga Trough which reaches about 2800 m deep in the mouth of the bay (Fig. 1). In eastern Suruga Bay, 286 females and 69 males of G. eastmani and 348 females and 370 males of G. nipponensis were fished between 150 and 450 m deep from 414 fishing tows. In western Suruga Bay, 292 females and 84 males G. eastmani were fished between 150 and 405 m deep from 159 fishing tows. However, only 26 females and 10 males of G. nipponensis were collected in western Suruga Bay. No G. eastmani were fished from 50 fishing tows in the north of 34°50¢N. In G. eastmani, females were collected more than males in both locations, although catch per unit of effort (CPUE; i.e. the number of individuals per tow) in the west was much higher than the east. In G. eastmani, CPUE of the mature specimens was much higher than the immature in both locations. Galeus nipponensis was more common in the east and the sex ratio in the east was almost similar (Table 2). In G. FISHERIES SCIENCE 814 T Horie and S Tanaka Table 2 Catch per unit of effort (CPUE) and range of total length in Galeus eastmani and G. nipponensis from the east and west of Suruga Bay G. eastmani East West G. nipponensis East West Female Immature Mature Total Total length (mm) 0.10 0.59 0.69 172–430 0.07 1.77 1.84 270–450 0.34 0.50 0.84 267–675 0.04 0.12 0.16 531–644 Male Immature Mature Total Total length (mm) 0.02 0.14 0.17 188–385 0 0.53 0.53 351–393 0.50 0.39 0.89 213–644 0.03 0.04 0.06 360–622 CPUE indicates number of specimens per number of fishing tows. nipponensis from the east, CPUE for the mature specimens was a similar value for the immature. Therefore, G. eastmani in the east and west were analyzed separately and G. nipponensis only in the east was analyzed. Reproduction Galeus eastmani Only the right ovary was functional in all specimens. Ovum weight (OW) increased exponentially with ovum diameter (OD) according to the following regression equations (Fig. 2). East: OW = 6.12 ¥ OD2.96 ¥ 10-4 (r = 0.964); West: OW = 9.89 ¥ OD2.79 ¥ 10-4 (r = 0.982). The regression curves for the east and west were similar. Ovum reached about 18 mm in diameter and about 3.2 g in weight in both locations. Ovum over 5 mm became yellow and contained yolk material. Diameter of the maximum ovum in each mature female ranged from 6 mm to 20 mm and those in females carrying an egg case in the oviduct ranged from 8 mm to 17 mm (Fig. 3). In sharks from the east, the shell gland began to develop at about 320 mm TL (Fig. 4). The outset of development of the shell gland was not observed in sharks from the west, because no individuals between 280 and 340 mm TL were collected. The ovary weight began to increase at about 350 mm TL after the development of the shell gland. Individuals with the shell gland over 10 mm in width and the ovary over about 3 g attained maturity. These individuals possessed thickened oviducts. During the former period, the minimum mature size of female was 354 mm TL in the east and 363 mm TL in the west, and the maximum immature size was 382 mm TL in the east and 368 mm TL in the west (Table 3). The percentage of mature females in the class interval of 360–370 mm TL was 50% in both locations. During the Fig. 2 Relationships between ovum diameter and ovum weight in Galeus eastmani from the (a) east [OW = 6.12 ¥ OD2.96 ¥ 10-4 (r = 0.964, n = 759)] and the (b) west [OW = 9.89 ¥ OD2.79 ¥ 10-4 (r = 0.982, n = 882)] and (c) G. nipponensis [OW = 1.05 ¥ OD2.79 ¥ 10-3 (r = 0.981, n = 805)]. latter period, minimum mature size of females was 343 mm TL in the east and 375 mm TL in the west, and the maximum immature size was 400 mm TL in the east and 391 mm TL in the west. The percentage of mature females in the class interval of 350–360 mm TL in the east was 50%. In the west, only one female in the class interval of 360–370 mm TL was immature and five specimens in the 370–380 mm TL were all mature. Size at sexual maturity of females from the east tended to be smaller than those from the west. In females from the east, maturity size during the former period was larger than the latter period. In contrast, maturity size in females from the west was almost similar between both periods. In male sharks from the east, claspers over 34 mm long were hardened and calcified. The calcified claspers was Reproduction and food habits of sawtail catsharks FISHERIES SCIENCE Fig. 3 Frequency distribution of diameter of maximum ovum in each mature female in (a) east and (b) west Galeus eastmani and (c) G. nipponensis. Shading indicates frequency distribution of diameter of maximum ovum in sharks with egg cases in oviduct. observed in individuals over 320 mm TL from the east, although a shark of 338 mm TL possessed the soft claspers (Fig. 5). A pair of testes in shark under 340 mm TL was less than 1 g. Sharks from the west possessed the calcified claspers over 35 mm long and most sharks had a pair of developed testes over 1 g. During the former period, the minimum mature size of male in the east was 322 mm TL and the maximum immature size was 328 mm TL of the two males in the class interval of 320–330 mm TL; one was mature while the other immature. However, males in the class interval of 330–340 mm TL were all mature. During the latter period, the minimum mature size of male in the east was 343 mm TL and the maximum immature size was 355 mm TL. Five males out of six in the class interval of 340–350 mm TL were mature. In males from the east, maturity size during the former period was smaller than the latter period. Maturity size of males was unknown from the west because only mature individuals over 815 Fig. 4 Relationships of total length to maximum width of shell gland and ovary weight in (a) east and (b) west Galeus eastmani and (c) G. nipponensis. (䊊), Shell gland; (+), ovary weight. 358 mm TL during the former period and 351 mm TL during the latter were fished. Ova of mature individuals showed considerable size variability in the month examined in both locations (Fig. 6). Large yolky ova were found almost every month in both locations. In the east, individuals with an egg case in the oviduct appeared from October to January (Table 4). The highest percentage of occurrence of egg cases was 16.7% in January, the second was 9.1% in December. In the west, the occurrence was 5.7% in February, 6.8% in April and 10.2% in October. No individual with egg cases was seen in the east in April and May nor in the west in May although we examined over 20 individuals at that time. Galeus nipponensis Only the right ovary was functional in all specimens. The relationship between ovum diameter and ovum weight was obtained as OW = 1.05 ¥ OD2.79 ¥ 10-3 (r = 0.981) (Fig. 2). The ova reached about 23 mm in diameter and about 7.0 g in weight. Ovum over 8 mm became FISHERIES SCIENCE 816 T Horie and S Tanaka Table 3 Number of immature and mature sharks by the class for female and male of Galeus eastmani and G. nipponensis during the former (1981–1989) and the latter (1992–1996) periods East Length (mm) Former period Immature Mature % West Latter period Immature Mature % Former period Immature Mature % Latter period Immature Mature % Female in G. eastmani <330 12 -340 2 -350 3 -360 4 -370 4 -380 1 -390 1 -400 0 -410 0 -420 0 420⬉ 0 0 0 0 1 4 19 32 26 24 2 1 0 0 0 20 50 95 97 100 100 100 100 4 2 3 2 1 1 0 0 1 0 0 0 0 2 2 10 16 16 37 33 17 3 0 0 40 50 91 94 100 100 97 100 100 1 0 1 4 1 0 0 0 0 0 0 0 0 0 0 1 0 7 3 16 9 9 0 – 0 0 50 – 100 100 100 100 100 0 0 0 2 1 0 0 1 0 0 0 0 0 0 0 0 5 12 37 56 47 79 – – – 0 0 100 100 97 100 100 100 Male in G. eastmani <320 5 -330 1 -340 0 -350 0 -360 0 -370 0 370⬉ 0 0 1 8 2 10 7 2 0 50 100 100 100 100 100 0 0 1 1 1 0 0 0 0 0 5 15 7 3 – – 0 83 94 100 100 0 0 0 0 0 0 0 0 0 0 0 3 8 10 – – – – 100 100 100 0 0 0 0 0 0 0 0 0 0 0 7 15 41 – – – – 100 100 100 G. nipponensis <500 72 -520 13 -540 8 -560 7 -580 9 -600 8 -620 0 620⬉ 0 0 0 0 1 7 20 37 48 0 0 0 13 44 71 100 100 20 1 0 2 0 1 0 0 0 0 0 0 3 13 31 47 0 0 – 0 100 93 100 100 100 12 9 9 0 0 0 0 0 3 1 6 8 14 6 6 0 20 10 40 100 100 100 100 42 7 11 12 6 1 0 0 0 0 0 2 9 33 48 25 0 0 0 14 60 97 100 100 % Indicates the rate of mature sharks in the class. yellow and contained yolk material. Diameter of the maximum ovum in each mature female ranged from 10 mm to 25 mm and that of female with egg cases ranged from 11 mm to 25 mm (Fig. 3). The shell gland began to develop at about 480 mm TL (Fig. 4). The ovary began to develop at about 560 mm TL after the development of the shell gland. Individuals with the shell gland over 14 mm in width and the ovary over about 25 g attained maturity. These individuals possessed thickened oviducts. During the former period, the minimum mature size of female was 556 mm TL and the maximum immature size was 598 mm TL. The percentage of mature females in the class interval of 580–600 mm TL exceeded over 70%, although those in the 560–580 mm TL was 44%. During the latter period, the minimum mature size of female was 567 mm TL, and the maximum immature size was 585 mm TL. Two females in the class interval of 540–560 mm TL were immature and three females in the class interval of 560–580 mm TL were mature. The percentage of mature females in the class interval of 580–600 mm TL was 93%. Maturity size of females during the former period tended to be a little larger than during the latter. In male sharks, the claspers began to extend rapidly at about 470 mm TL, and most claspers over 90 mm long were hardened and calcified (Fig. 5). The calcified claspers were observed in individuals over 490 mm TL. Testes weight also began to increase at about 500 mm TL. Most males over 570 mm TL possessed a pair of testes above 5 g. Individuals with a pair of testes above 4 g and calcified clasper over 90 mm long attained maturity. During the former period, the minimum mature size of males was 514 mm TL, and the maximum immature size was 549 mm TL. The percentage of mature males in the class interval of 540–560 mm TL was 40% and eight individuals in the 560–580 mm TL were all mature. In the latter period, the minimum mature size of males Reproduction and food habits of sawtail catsharks FISHERIES SCIENCE 817 Table 4 Frequency of occurrence of mature individuals with egg cases by month in Galeus eastmani and G. nipponensis G. eastmani East West F(%) n F(%) September October November December January February March April May 0 6.5 5.0 9.1 16.7 0 0 0 0 13 93 20 11 12 6 17 32 44 – 10.2 0 0 – 5.7 0 6.8 0 n – 59 3 9 – 35 4 148 23 G. nipponensis F(%) n 5.9 10.7 18.2 36.4 41.7 9.1 7.1 20.6 10.8 17 28 33 22 12 11 14 34 37 F(%), percentage by frequency of occurrence; n, total number of mature individuals in each month. Fig. 5 Relationships of total length to clasper length and testes weight in Galeus eastmani from the (a) east and (b) west and (c) G. nipponensis. (䊊), Calcified clasper; (䉱), soft and not calcified clasper; (+), testes. was 546 mm TL, and the maximum immature size was 583 mm TL. The percentage of mature males in the class interval of 540–560 mm TL was 14% and that in the 560–580 mm TL was 60%. Maturity size of males in the former period was a little smaller than in the latter. Monthly changes of the maximum ovum diameter in mature individuals indicated a similar tendency to G. eastmani, as large yolky ova were found almost every month (Fig. 6). Individuals with egg cases in the oviduct appeared every examined month (Table 4). The highest occurrence of egg cases was 41.7% in January, and the second highest was 36.4% in December. Food habits Galeus eastmani There were no significant seasonal differences in the index of stomach fullness (ISF) (Fig. 7). The median of ISF for females from the east in each month ranged from 1.6% to 3.9% and males from 1.1% to 2.8%. The maximum ISF for females tended to be high in October and November. The median of ISF for females from the west in each month ranged from 1.9% to 7.6% and males from 1.4% to 3.5%. The median of ISF for females from the west in March and April was higher than that from the east. The maximum ISF for females from the west in October was as high as that in the east. There was only one female with an empty stomach in each location, respectively. Main food items were Osteichthyes, Cephalopoda, and Crustacea in both sexes and both locations (Table 5). They preyed mainly on myctophid fishes, cephalopods (Sepiolidae spp. and Enoploteuthidae spp.) and crustaceans (Aegidae spp., Amphipoda spp., Euphausiacea spp., and Decapoda spp.). Non-food items were vegetable, vinyl etc. They preyed on schooling pelagic species such as Engraulis japonicus. These foods were mostly observed as pieces of fish meat. The number of prey species below the family level found in the female and male specimens in the east was at least 5 and 0 in Osteichthyes, 4 and 3 in Cephalopoda, and 21 and 6 in Crustacea, respectively. The number in the west was also 3 and 0 in Osteichthyes, 6 and 3 in Cephalopoda, and 19 and 17 in Crustacea, respectively. Females preyed on more various species than males in both locations, especially for Crustacea. Both females and males from the east fed on more species of Osteichthyes and Crustacea than Cephalopoda, and contained more non-food items in the stomach than those from the west, particularly for males. In the west, females and males fed on more Crustacea and Cephalopoda than Osteichthyes. However, as shown in the parentheses of Table 5, when the 120 females and 27 males collected from the west from only one survey day in April 1996 were excluded from the total sample, the %F and %W of Osteichthyes became higher than those of Cephalopoda as in sharks from the 818 FISHERIES SCIENCE T Horie and S Tanaka Fig. 6 Monthly changes of diameter of maximum ovum in Galeus eastmani from the east (䊊) and west (䉭) and G. nipponensis (䊐). Symbols and extent bars indicate median and range. east. Crustacea in the west showed higher values over 50% in %W than in the east. In females and males from the east, there were no significant seasonal differences in RI (Fig. 8). Osteichthyes and Crustacea indicated higher RI over 2100 throughout three seasons, respectively. Females from the west had seasonal changes in RI. Osteichthyes indicated the highest RI of 6058 in autumn. The RI of Cephalopoda in spring showed the highest value of 2294. Crustacea indicated the highest RI of 6852 in spring. As noted above, we collected many specimens from only one survey day in April 1996. Among them, 116 females had fed on a total of 5924 Euphausiacea (375 g) and 48 females also fed on Watasenia scintillans (114.8 g). Cephalopoda caught in spring, when excluded from the above specimens, indicated a lower RI of 41. Males from the west also indicated seasonal changes in RI. Osteichthyes indicated the highest RI of 3561 in autumn. Crustacea in winter and spring indicated a higher RI of 8596 and 8032, respectively. Cephalopoda in spring indicated the highest RI of 1491. However, among the specimens in spring, 26 males collected in April 1996 fed on a total of 732 Euphausiacea (42 g), and 25 males also fed on Cephalopoda (15 g). The RI of Cephalopoda became 0 in spring, excluding the 27 males. Galeus nipponensis There were no significant seasonal differences in ISF (Fig. 7). The median of ISF for young and immature females in each month ranged from 1.6% to 4.5% and for males from 3.0% to 6.1%. The maximum ISF over 10 was observed in October, November and January for females, and in September, October, March and April for males. The median of ISF for mature females in each month ranged from 1.1% to 4.6% and for males from 2.5% to 4.9%. The maximum ISF over 10 was observed in April for females, and in September, November and February for males. Only one female and one male had an empty stomach. Main food items were Osteichthyes, Cephalopoda and Crustacea in both sexes (Table 5). Sharks preyed mainly on Osteichthyes (Sardinops melanostictus, Glossandon semifasciatus, Chlorophthalmus albatrossis and Myctophidae spp.), Cephalopoda (Sepiolidae spp. and Enoploteuthidae spp.) and Crustacea (Aegidae spp., Euphausiacea spp. and Decapoda spp.). They preyed on schooling pelagic species such as Sardinops melanostictus, Engraulis japonicus, Carangidae spp. and Scombridae spp. These foods were found to be in pieces as for G. eastmani. The number of prey species below the family level found in the female and male specimens was at least 16 Reproduction and food habits of sawtail catsharks FISHERIES SCIENCE 819 Fig. 7 Monthly changes of index of stomach fullness (ISF) for Galeus eastmani in the (a) east and (b) west and (c) immature including young and (d) mature G. nipponensis. (䊊), Female; (¥), male. Symbols and extent bars indicate median and range. Fig. 8 Seasonal changes of ranking index of foods in (a) female and (b) male of Galeus eastmani from the east and west of Suruga Bay. Osteichthyes in the east (䊊) and the west (䊉); Cephalopoda in the east (䉭) and the west (䉱); Crustacea in the east (䊐) and the west (䊏). Symbols in parentheses indicate the values without specimens in April 1996. and 23 in Osteichthyes, seven and 11 in Cephalopoda, and 16 and 19 in Crustacea, respectively. Males tended to prey on more various species than females. Osteichthyes indicated high %W over 60% in both female and male. The %W of Cephalopoda in females was higher than that of Crustacea. However, this relationship was reversed in males. Non-food items appeared in about 30% of both females and males. The young females indicated seasonal changes in RI (Fig. 9). Osteichthyes showed the highest RI of 7319 in autumn. However, RI of Osteichthyes in winter and spring were low. Crustacea in winter and spring indicated a high RI of 4235 and 5614, respectively. In mature females there were no significant seasonal differences in RI. Osteichthyes indicated a high RI over 4700 throughout three seasons. The young males had seasonal changes in RI. Osteichthyes indicated higher RI over 1900 throughout three seasons. Crustacea indicated the highest RI of 5287 in winter. Cephalopoda indicated the highest RI of 2915 in spring. Food items of the highest RI in autumn, winter and spring changed in Osteichthyes, Crustacea and Cephalopoda, respectively. In immature males, there were no significant seasonal differences in RI. Osteichthyes indicated the highest RI of over 6400 throughout three seasons. In mature males, the RI of Osteichthyes indicated a similar tendency as immature males and mature females. Thus, young sharks in both sexes changed food items seasonally as did G. eastmani from the west. However, immature and mature sharks, which were of a larger size than G. eastmani, always preyed on Osteichthyes principally. G. eastmani G. nipponensis Female %F 88.7 40.9 41.9 8.9 n %F 98 64.9 (85.3) 81 20.1 (23.5) 0.6 3.5 1.7 1.7 2.8 0.5 4.7 4 2 2 0.9 0.9 0.3 0.7 1 1 6.1 6.2 7 0.6 (2.9) 0.6 (2.9) 4.5 0.6 (2.9) 17.9 59.7 (85.3) West %W 8.1 (45.3) 2.5 (12.8) 0.1 0.1 (1.5) 1.8 (19.1) 1.5 0.4 (3.9) 1.7 (8.1) n 51 (16) 39 (13) 1 1 (1) 1 (1) East %F %W n 84.6 31.3 12 19.2 6.7 11 3.8 3.1 1 %F 45.5 (64.7) 13.6 (5.9) 4.5 (5.9) Female West %W 3.1 (21.5) 0.8 (0.5) 1.0 (8.9) 8 n %F 9 (3) 7 (2) 88.6 61.4 61.8 11.1 4.3 5.6 2.9 4.3 0.4 2.3 2 (1) %W Male n %F %W n 176 94.2 127 26.0 1.9 3 3.2 65.1 10.6 0.6 6.1 229 84 3 5 5.8 5.8 2.6 2.6 0.9 3.5 13 12 5 0.6 0.2 4 3.2 0.6 0.4 0.1 5 1 10.5 37 2 3 1.4 0.5 1 1.4 5.7 10.0 8.2 1 19 12.3 1.4 1.4 5.7 4.0 1.3 3.2 0.1 2 3.5 0.1 37 1 1.4 0.2 1 1.3 1 8 16.9 0.6 1 0.6 0.6 1 0.6 1.3 1.3 0.2 0.0 0.2 1 2 2 0.6 0.02 1 0.6 0.6 0.6 0.6 0.6 0.5 0.2 0.2 0.2 0.1 2 1 1 1 1 1.3 0.6 1.9 0.6 92.9 2.2 1.0 1.3 0.4 18.8 2 1 3 1 1 (1) 84.6 21.5 40.9 (64.7) 1.4 (12.2) 1.4 0.8 1 1.4 1.4 1.4 1.4 1.4 0.1 0.4 0.1 1.1 0.4 1 1 1 1 1 2.9 4.7 3 7.3 T Horie and S Tanaka 87.0 Male FISHERIES SCIENCE Total of Osteichthyes Osteichthyes spp. Anguilliformes spp. Sardinops melanostictus Engraulis japonicus Euteleostei spp. Glossanodon semifasciatus Stomiiformes spp. Maurolicus muelleri Sternoptychinae sp. Polyipnus stereope Phosichthyidae sp. Chlorophthalmus albatrossis Neoscopelidae spp. Neoscopelus sp. Myctophidae spp. Benthosema pterotum Hygophum sp. Symbolophorus evermanni Diaphus garmani Chaunax abei Zenion japonicum Macroramphosus scolopax Scorpaenidae sp. Triglidae sp. Lepidotrigla spp. Peristedion orientale Carangidae spp. Decarterus tabl Cepola schlegeli Champsodon snyderi Foetorepus sp. Benthodesmus tenuis Scombridae spp. Paralichthydae sp. Pleuronectidae spp. Tanakius kitaharai Osteichthyes spp. unit East %W 820 Table 5 Percentage by frequency of occurrence (%F), percentage by weight (%W) and number of individuals (n) in each food item for female and male of Galeus eastmani and G. nipponensis Continued G. eastmani G. nipponensis Female 55.7 19.7 3.5 4.2 1.7 7.8 2.6 0.5 0.1 2.4 0.9 0.7 13.9 0.4 4.3 6.1 West %W n 55 86.4 (55.9) 1.3 4 9.1 23.4 (1.5) 0.1 2.8 384 (10) 2 17 2 2.6 (5.9) 13 14.3 3 0.6 0.6 (2.9) 0.4 (0.04) 0.1 0.3 0.001 (0.01) 4 (2) 27 2 1 (1) n %F 0.6 5.0 92.2 4.3 2.6 28.7 0.2 2.3 17.4 7.8 2.5 1.3 20.0 0.9 13.0 53.9 0.9 1.0 0.1 0.9 6.8 0.2 0.1 7.7 %F 8.5 19 65.9 (23.5) 17.7 (5.7) 2.3 0.9 6.8 3.4 0.2 2 2.3 Male n %F %W n 39 (1) 1 3 51.4 9.0 38 60.4 2.9 0.6 5 1 4.3 5.7 0.5 1.7 4 4 1.4 0.02 1 0.02 %F 25 56.5 (17.6) 5 31.2 2 1.3 81.2 (41.2) 380 92.9 (73.5) 5 0.6 3 0.5 (0.4) 14.1 0.05 0.01 5.2 (1.1) 261 (7) 11.5 0.2 3 60 8 3.8 2 0.4 14 20.1 0.04 53 4.5 4.0 2 1.4 1.8 6 10.4 0.6 3.7 0.2 28 1 2.9 1.4 0.1 0.003 2 1 1.9 0.03 4 0.6 0.01 1 0.6 4.2 1 1.9 47.4 0.2 2.6 3 172 66.2 1.3 1 1.3 9.7 0.1 0.5 283 2 2 7.8 0.2 16 0.6 3.2 0.02 0.02 1 6 1 17.7 0.1 0.1 0.1 1 2 3 11.5 3.8 6 45 10.4 2 50 85.1 (35.3) 154 35.7 (38.2) 1 0.2 26 19.2 1.3 7 20.5 (29.4) 1 20.1 (8.8) 2.6 (0.2) 42 (7) 12 1 1 4 6 13 1 2 6 0.1 2.3 (5.88) 0.04 (0.4) 7.7 13 63.9 (23.5) 8.9 (0.9) 7.7 1.4 23.1 10.2 0.7 0.1 0.4 0.2 0.01 2.7 0.1 0.02 1.3 7.1 67.3 (51.0) 6261 (101) 76.9 27.3 36 93.2 (82.4) 78.8 (68.7) 795 (29) 67.1 0.02 1 3.8 0.3 1 3.8 0.1 1 1.4 5980 (56) 84 (25) 6.5 0.6 0.6 2.6 3.2 8.4 0.6 1.3 3.9 31 0.8 3.4 46.4 (4.8) 3.0 (7.9) 137 0.5 0.6 0.6 1.9 23 9 16.6 n 31.8 1.4 37.1 23.1 %W 1 (1) 11.4 0.6 (5.3) 1.3 0.8 0.4 4.9 1.4 3.8 3.3 12 12 (6) 6 68.2 57.9 741 4.3 8 34.1 (52.9) 6.1 (14.0) 23 (11) 34.3 4.5 1 3 4.3 0.8 27 8.4 88 42.9 1.9 1 1.9 4 0.6 0.2 1.9 0.4 43 154 3 0.3 3 0.03 1 821 0.9 42.3 n West %W 1 5.2 1.7 40.0 East %F %W Female FISHERIES SCIENCE Total of Cephalopoda Cephalopoda spp. Coleoidea spp. Sepiidae sp. Sepiadarium kochii Sepiolidae spp. Sepiolidae spp. beak Sepiolina nipponensis Loliginidae spp. Loliginidae spp. beak Enoploteuthidae spp. Enoploteuthidae spp. beak Watasenia scintillans Onychoteuthidae sp. beak Gonatidae spp. beak Histioteuthidae spp. beak Ommastrephidae sp. beak Ommastrephes bartrami Octopoda spp. Cephalopoda spp. unit Total of Crustacea Cirolana japonensis Bathynomus doederleini Argathona japonica Aegidae spp. Aega antillensis Rocinela maculata Amphipoda spp. Gammaridae spp. Euphausiacea spp. Decapoda spp. Haliporoides sibogae Aristeidae sp. Trachypenaeus curvirostris Sergestes lucens %F East %W Male Reproduction and food habits of sawtail catsharks Table 5 Table 5 Continued %F G. nipponensis n %F 24.7 1.9 0.9 1.9 1 0.9 11.3 12.2 0.2 1.5 2.8 1 19 17 0.9 0.9 8.7 1.7 0.1 0.1 0.4 0.2 1 1 11 3 4.3 0.7 5 Male West %W 6.1 1.0 n East %F %W n 69 3 6.8 0.6 (2.9) 0.6 (2.9) 1.9 (2.9) 2.6 (27.1) 0.2 (2.0) 0.3 (0.7) 1 (1) 1 (1) 3 (1) 7.1 6.5 (5.9) 1.2 0.8 (1.7) 20 10 (2) 11.5 3.6 5 1.9 (2.9) 0.6 (2.9) 0.6 (2.9) 1.9 0.1 (0.3) 0.02 (0.2) 0.03 (0.3) 0.2 4 (2) 1 (1) 2 (2) 4 3.8 0.9 1 0.4 2 0.9 0.02 1 2.6 11.3 0.5 1.1 3 19 0.9 0.1 1 0.9 0.1 1 0.9 0.02 1 13.0 39.1 5.2 0.9 0.9 1.1 2.2 1.3 0.3 0.02 4.5 (5.9) 29.9 (17.6) 5 7.1 (0.1) 1 1 1.3 2.3 3.8 0.6 (2.9) 0.6 0.2 (1.8) 0.0 1 (1) 1 0.6 (2.9) 0.1 (1.0) 1 (1) 11.4 2.3 (5.9) 0.5 1 2.3 2.3 (5.9) 2.6 0.9 0.9 0.02 37.4 8.4 115 261.4 3 0.6 (2.9) 5.8 (5.9) 0.6 13 (23.5) 154 (34) Value in parentheses excluded specimens in April 1996. 0.001 (0.01) 0.3 (0.6) 1.7 (2.4) 0.2 (0.7) 0.01 0.2 (0.7) 0.002 0.9 (1.5) 815.4 (77.9) West %W 3.2 2.0 1.9 (20.7) 0.2 0.1 0.3 (3.6) n 11 (2) 1.4 3.8 0.7 6.8 (11.8) 1.0 (8.5) 22.7 (35.3) 2.1 (11.4) 1 2.3 (5.9) 0.4 (4.1) %F %W %F %W 2.9 0.6 2 1.4 1.4 0.5 0.2 1 1 1.3 0.5 2 5.7 1.4 4.3 5.7 1.5 0.1 0.1 0.7 5 3.2 1 0.6 3 4.5 4 11.7 0.6 0.6 0.3 0.1 0.1 0.7 0.1 0.1 5 1 7 18 1 1 8 2 (2) 2.9 0.03 2 1.3 3.9 0.1 0.1 2 6 0.6 0.1 1 2.9 1.4 0.2 0.003 2 1 4.3 5.7 0.2 1.7 3 8 0.6 2.6 0.01 0.1 1 5 1.4 0.04 1 1.4 0.04 1 0.1 1.4 0.1 0.01 2.7 0.2 1.0 0.5 1 1 2.9 25.7 1.4 0.6 0.6 4 3.9 26.0 1 5.2 0.6 0.6 1 2.6 1.3 29.2 154 0.001 0.03 0.4 0.004 9.0 1576 1 1 4 1 1 3.8 0.7 26.9 32.2 26 12.8 1 2.3 (5.9) 0.4 (4.1) 44 (17) 81.9 (7.57) n 1 (1) 1 (1) 2 11 (2) n 3 1 (1) 7.7 38.5 3.8 Male 1 (1) 1.4 0.1 34.3 70 11.3 599.3 6 T Horie and S Tanaka 1.7 %F Female FISHERIES SCIENCE Oplophoridae spp. Oplophorus gracilirostris Systellaspis debilis Plesionika grandis Plesionika martia Heterocarpus spp. Heterocarpus sibogae Crangonidae spp. Crangon sagamiensis Nephropidae sp. Nephropsis stewarti Polycheles typhlops Palinuridae sp. Scyllaridae spp. Scyllarus cultrifer Scyllarides squamosus Diogenidae spp. Axiidae spp. Parapagurus monstrosus Galatheidae sp. Munida japonica Brachyura spp. Megalopa Dorippidae sp. Goneplax renoculis Pseudosquilla ciliata Pseudosquillopsis dofleini Squillidae sp. Squilloides leptosquilaa Brachyura spp. unit Crustacea spp. unit Other Amphinomidae sp. Ophiuroidea spp. Holothroidea sp. Polychaeta spp. Polychaeta spp. unit Non-food items Total (No. of specimens and weight, g) East %W 822 G. eastmani Female Reproduction and food habits of sawtail catsharks FISHERIES SCIENCE 823 DISCUSSION Fig. 10 Monthly changes of water temperature by depth during the former (1981–1989) and the latter (1992–1996) periods in the (a) east side and (b) west side of Suruga Bay (from Fisheries Experiment Station of Shizuoka11–13). 150 m in depth during the former period (䊊) and the latter (䊉); 200 m in depth during the former period (䊐) and the latter (䊏); 250 m in depth during the former period (䉭) and the latter (䉱); 300 m in depth during the former period (䉬) and the latter (䉫). The ovum was considered to be ovulated between 18– 20 mm in G. eastmani and between 20–25 mm in G. nipponensis. Both species of Galeus with egg cases had yolky ova over 8 mm in diameter. The interval of laying egg cases in Scyliorhinus retifer ranged from 14.1 to 16.7 days for the mean rate.10 Large yolky ova of both species of Galeus with egg cases would be ovulated again after a few weeks. Size at sexual maturity of both species of Galeus differed between the former and latter periods. It is generally known that size at sexual maturity in fishes changes according to the population size and environmental conditions. In Suruga Bay, the monthly average of water temperature at every 50 m in depth from 150 to 300 m, where both species of Galeus inhabit, differed between the former and latter periods. Namely, those in April and May during the latter period were higher by about 1°C than during the former period (Fig. 10).11–13 Size at sexual maturity of Mustelus manazo tended to become larger with the decline in water temperature.14 The change of maturity size in both species may be caused by the change of physical environments. However, further investigation of both biological and environmental information is needed to elucidate the variation. Female G. eastmani, collected off Kochi, possessed a fully developed ovary and shell gland over 368 mm TL, and female G. nipponensis also had fully mature gonads over 556 mm TL.1 The minimum size of mature individuals in female G. eastmani in the west and female G. nipponensis in Suruga Bay Fig. 9 Seasonal changes of ranking index of foods in (a) young, (b) immature and (c) mature of female and male Galeus nipponensis. Osteichthyes in female (䊊) and male (䊉); Cephalopoda in female (䉭) and male (䉱); Crustacea in female (䊐) and male (䊏). 824 FISHERIES SCIENCE was almost the same as the size at sexual maturity in both species from Kochi. For G. eastmani, size at sexual maturity differed between the east and west of Suruga Bay. Distance between the east and west fishing grounds was only about 10 km. However, there is the Suruga Trough reaching over 2000 m deep between both fishing grounds, and no G. eastmani were fished in the innermost recesses of Suruga Bay. The CPUE of G. nipponensis differed a great deal between both locations which may indicate a rare interchange of populations between the east and west. Both species of Galeus tended to ovulate throughout the year. Occurrence of egg cases in G. eastmani from the east showed a bias by month. Galeus nipponensis possessed egg cases in all examined months, and they indicated the higher occurrence rate in December and January. Scyliorhinus canicula, belonging to Scyliorhinidae as Galeus, from the Menai Straits and the Adriatic, deposits egg cases throughout the year with maximum intensity in spring and a minimum in the fall.15,16 In S. canicula, maximum feeding intensity lags behind or precedes the most intensive spawning periods.16 Thus, S. canicula has the most intensive spawning periods in spite of ovulating all year round. This may be caused by an interval of egg cases deposition. Interval of egg cases deposition in Scyliorhinus retifer ranged from 14.1 to 16.7 days for the mean rate and changed in water temperature.10 Galeus sauteri inhabits the bottom layer where water temperature remains constant throughout the year, and it is believed that this species deposits egg cases all year round.17 Monthly averages of water temperature at every 50 m depth from 150 to 300 m in Suruga Bay in the examined years indicated a lower value from August to September and a higher value from October to January, and the difference between the higher and lower temperatures was about 2°C (Fig. 10).11–13 Thus, water temperature in Suruga Bay showed little fluctuation through the year. Therefore, both species may have a bias in occurrence of egg cases in the oviducts. A few sharks in both Galeus preyed on schooling pelagic species such as Sardinops melanostictus, Engraulis japonicus, Carangidae spp. and Scombridae spp. Cephaloscyllium umbratile from Choshi, Japan also preyed frequently on schooling pelagic species such as sardine and mackerel.6 Scyliorhinus canicula is known to be nocturnally active.18 Compagno8 hypothesized that the nocturnal activity pattern of the sluggish and weakswimming S. canicula enable it to catch day-active bony fishes that lie on the bottom at night and are relatively inactive and unresponsive. In adult G. melastomus, pieces of prey too large in relation to a predator’s size may indicate that they hunt in groups.19 Schooling pelagic fishes observed in the stomach from both species of Galeus were mostly pieces. The pieces were too large in size for the sharks to have bitten off of those fishes, because the teeth of these sharks are not suitable for such cutting. Therefore, both species seemed to swallow T Horie and S Tanaka pieces of pelagic fishes, which were already cut off, in the same way as non-food items. It is unknown how the pieces are derived. Both species preyed on various organisms. Galeus melastomus from the western Mediterranean also fed on a wide variety of prey, and their foods differed by depth for a change in available food resources.19 Galeus polli and five species of Scyliorhinidae from the west coast of southern Africa preyed mainly on Osteichthyes.20 Galeus eastmani in the east preyed mainly on Osteichthyes and Crustacea throughout three seasons. In contrast, G. eastmani in the west preyed mainly on Crustacea in winter and spring seasons. Galeus eastmani, caught in April 1996 from the west, foraged much more Cephalopoda (especially Watasenia scintillans) and Crustacea (especially Euphausiacea spp.). Watasenia scintillans seems to have aggregated for preying on Euphausiacea spp. Thus, G. eastmani also may eat different types of prey between locations for a change in available food resources. Immature and mature specimens of G. nipponensis were primarily piscivorous throughout three seasons. However, the young of G. nipponensis differed in their foods between seasons, and preyed on different foods from G. eastmani in the same location. The young of G. nipponensis also preyed on various organisms. These may indicate that G. eastmani and the young of G. nipponensis change prey items to avoid food competition between them. We have concluded from the diet composition that both species are voracious and opportunistic feeders. ACKNOWLEDGMENTS We are grateful to Dr GM Cailliet, Moss Landing Marine Laboratories, for his review and linguistic correction of the first draft. We also thank Katsumi Yamada, captain of the trawl boat Hinode maru, and the crew for their help with sample collection. REFERENCES 1. Nakaya K. Taxonomy, comparative anatomy and phylogeny of Japanese catsharks, Scyliorhinidae. Mem. Fac. Fish. Hokkaido Univ. 1975; 23: 1–94. 2. Tachikawa H, Taniuchi T. Galeus longirostris, a new species of the sawtail catshark from Japan. Jpn. J. Ichtyol. 1987; 33: 352–359. 3. Shirai S, Hagiwara S, Nakaya K. Scyliorhinus tokubee sp. nov. Southern Japan (Scyliorhinidae, Elasmobranchii). Jpn. J. Ichtyol. 1992; 39: 9–16. 4. Kudo S. Sexual maturity and embryo in Halaelus buergeri. Rep. Nankai Reg. Fish. Res. Lab. 1959; 11: 41–45 (in Japanese). 5. Makihata N. Development and nutrition in embryo and young in oviparous blackspotted dogfish Halaelus buergeri (Müller et Henle). Rep. Jpn. Soc. Elasmobranch Stud. 1984; 18: 12–25. 6. Taniuchi T. Aspects of reproduction and food habits of the Japanese swellshark Cephaloscyllium umbratile from Choshi, Japan. 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