Reproduction and Food Habits of Two Species of Sawtail Catsharks, Galeus Eastmani and G

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 1981Ð1989 and 1992Ð1996. 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 reproductive cycle is unknown. There have not been specific studies on their reproduction or food habits. The sawtail catsharks belonging to the genus Galeus Thus, the influence the Galeus species may have on consist of four species around Japan, G. eastmani, G. other aquatic organisms in bottom communities is sauteri, G. nipponensis, and G. longirostris. These four unknown. It is important to evaluate their interrelation- species inhabit the upper continental slope off Japan and ships with other aquatic organisms. This study provides are caught incidentally with commercial trawl and the first detailed information on the reproduction and bottom long-line fisheries. In Suruga Bay, G. eastmani food habits of G. eastmani and G. nipponensis in Suruga and G. nipponensis are often caught with bottom trawl- Bay. net together with other elasmobranchs, Cephaloscyllium umbratile, Etmopterus brachyurus and E. molleri etc. However, they are usually discarded. MATERIALS AND METHODS In Japan, only a few studies have been conducted on scyliorhinid sharks, including species of Galeus, despite A total of 731 (578 female and 153 male) G. eastmani there being 17 species, which makes the group the third and 754 (374 female and 380 male) G. nipponensis were most numerous among Japanese shark families. These sampled by commercial bottom trawlers in Heda port in studies have been on their taxonomy,1–3 reproduction4–6 western Izu Peninsula between April 1981 and May 1996 and food habits.6 Biological information on both species (Table1), with the exception of 1990 and 1991 which of Galeus is merely limited to classification.1,7,8 The could not be sampled between June and August because reproductive mode of both species is oviparity, and their of seasonal closure for the trawl fishery. Seasons were divided into: (i) autumn (between September and November); (ii) winter (between December and Febru- *Corresponding author: Tel: 81-0543-34-0411. Fax: 81-0543-37- ary); and (iii) spring (between March and May). Fishing 0239. Email: [email protected] operation usually included six tows per day. For each, the Received 1 July 1999. Accepted 17 April 2000. fishing location and depth were recorded. Reproduction and food habits of sawtail catsharks FISHERIES SCIENCE 813

Table1 Number of specimens in Galeus eastmani and G. nipponensis examined in this study Month G. eastmani G. nipponensis Female Male Female Male East West East West September 16 0 5 0 19 19 October 96 63 15 34 74 88 November 23 3 4 0 50 31 December 13 10 1 2 30 16 January 16 0 2 0 42 40 February 8 36 0 4 12 34 March 27 5 4 0 37 48 April 34 151 8 37 53 45 May 53 24 30 7 57 59 Total 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 Fig. 1 Map showing sampling area (shaded) of Galeus eastmani and G. nipponensis in Suruga Bay, Japan. 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 numer- parison of food habits by similar size on G. eastmani, ous specimens: because the maximum size of G. eastmani in the east was (1) Immature. Ovary is thin and has no yolky ova. 430 mm TL. 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 RESULTS gland is well developed. The maximum width of shell gland is greater than 10 mm in G. eastmani and 14 mm Catch condition in G. nipponensis. Sexual maturity for males was assessed using the fol- Fishing occurred between 90 and 450 m on the east side lowing criteria: and from 52 to 405 m in depth on the west side of (1) Immature. The claspers are short, soft and not Suruga Bay, which are separated by Suruga Trough calcified. which reaches about 2800 m deep in the mouth of the (2) Mature. Stem cartilage of the claspers becomes bay (Fig. 1). hard or calcified. In eastern Suruga Bay, 286 females and 69 males of The research period of 1981–1996 was separated into G. eastmani and 348 females and 370 males of G. nippo- two periods to determine any change of size at sexual nensis were fished between 150 and 450 m deep from 414 maturity owing to the long period. The former period is fishing tows. In western Suruga Bay, 292 females and 84 1981–1989 and the latter is 1992–1996. males G. eastmani were fished between 150 and 405 m Stomach contents were examined in detail on the deep from 159 fishing tows. However, only 26 females specimens caught after 1993. Food items were identified and 10 males of G. nipponensis were collected in western to the lowest taxonomic level possible, and their number Suruga Bay. No G. eastmani were fished from 50 fishing and weight were recorded. tows in the north of 34°50¢N. In G. eastmani, females Index of stomach fullness (ISF) was obtained by using were collected more than males in both locations, the following formula: ISF = (SCW/BW) ¥ 100. although catch per unit of effort (CPUE; i.e. the number Ranking index (RI) of stomach contents was obtained of individuals per tow) in the west was much higher than from the following formula:9 RI = %F ¥ %W (%F: per- the east. In G. eastmani, CPUE of the mature specimens centage by frequency; %W; percentage by weight). was much higher than the immature in both locations. For immature G. nipponensis, individuals under Galeus nipponensis was more common in the east and the 430 mm TL were defined as the young stage for the com- sex ratio in the east was almost similar (Table2). In G. 814 FISHERIES SCIENCE T Horie and S Tanaka

Table2 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 G. nipponensis East West East West Female Immature 0.10 0.07 0.34 0.04 Mature 0.59 1.77 0.50 0.12 Total 0.69 1.84 0.84 0.16 Total length 172–430 270–450 267–675 531–644 (mm) Male Immature 0.02 0 0.50 0.03 Mature 0.14 0.53 0.39 0.04 Total 0.17 0.53 0.89 0.06 Total length 188–385 351–393 213–644 360–622 (mm)

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 Fig. 2 Relationships between ovum diameter and ovum similar. Ovum reached about 18 mm in diameter and weight in Galeus eastmani from the (a) east [OW = 6.12 ¥ OD2.96 about 3.2 g in weight in both locations. Ovum over 5 mm ¥ 10-4 (r = 0.964, n = 759)] and the (b) west [OW = 9.89 ¥ OD2.79 became yellow and contained yolk material. Diameter of ¥ 10-4 (r = 0.982, n = 882)] and (c) G. nipponensis [OW = 1.05 ¥ the maximum ovum in each mature female ranged from OD2.79 ¥ 10-3 (r = 0.981, n = 805)]. 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 latter period, minimum mature size of females was develop at about 320 mm TL (Fig. 4). The outset of 343 mm TL in the east and 375 mm TL in the west, and development of the shell gland was not observed in the maximum immature size was 400 mm TL in the east sharks from the west, because no individuals between and 391 mm TL in the west. The percentage of mature 280 and 340 mm TL were collected. The ovary weight females in the class interval of 350–360 mm TL in the began to increase at about 350 mm TL after the devel- east was 50%. In the west, only one female in the class opment of the shell gland. Individuals with the shell interval of 360–370 mm TL was immature and five gland over 10 mm in width and the ovary over about 3 g specimens in the 370–380 mm TL were all mature. Size attained maturity. These individuals possessed thickened at sexual maturity of females from the east tended to be oviducts. smaller than those from the west. In females from the During the former period, the minimum mature size east, maturity size during the former period was larger of female was 354 mm TL in the east and 363 mm TL in than the latter period. In contrast, maturity size in the west, and the maximum immature size was 382 mm females from the west was almost similar between both TL in the east and 368 mm TL in the west (Table3). The periods. percentage of mature females in the class interval of In male sharks from the east, claspers over 34 mm long 360–370 mm TL was 50% in both locations. During the were hardened and calcified. The calcified claspers was Reproduction and food habits of sawtail catsharks FISHERIES SCIENCE 815

Fig. 4 Relationships of total length to maximum width of shell gland and ovary weight in (a) east and (b) west Galeus eastmani Fig. 3 Frequency distribution of diameter of maximum ovum and (c) G. nipponensis. (), Shell gland; (+), ovary weight. 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 358 mm TL during the former period and 351 mm TL oviduct. during the latter were ﬁshed. Ova of mature individuals showed considerable size variability in the month examined in both locations (Fig. observed in individuals over 320 mm TL from the east, 6). Large yolky ova were found almost every month in although a shark of 338 mm TL possessed the soft both locations. In the east, individuals with an egg case claspers (Fig. 5). A pair of testes in shark under 340 mm in the oviduct appeared from October to January (Table TL was less than 1 g. Sharks from the west possessed the 4). The highest percentage of occurrence of egg cases was calciﬁed claspers over 35 mm long and most sharks had 16.7% in January, the second was 9.1% in December. In a pair of developed testes over 1 g. the west, the occurrence was 5.7% in February, 6.8% in During the former period, the minimum mature size April and 10.2% in October. No individual with egg of male in the east was 322 mm TL and the maximum cases was seen in the east in April and May nor in the immature size was 328 mm TL of the two males in the west in May although we examined over 20 individuals class interval of 320–330 mm TL; one was mature while at that time. 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 Galeus nipponensis was 343 mm TL and the maximum immature size was 355 mm TL. Five males out of six in the class interval of Only the right ovary was functional in all specimens. 340–350 mm TL were mature. In males from the east, The relationship between ovum diameter and ovum maturity size during the former period was smaller than weight was obtained as OW = 1.05 ¥ OD2.79 ¥ 10-3 (r = the latter period. Maturity size of males was unknown 0.981) (Fig. 2). The ova reached about 23 mm in diam- from the west because only mature individuals over eter and about 7.0 g in weight. Ovum over 8 mm became 816 FISHERIES SCIENCE T Horie and S Tanaka

Table3 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 West Length Former period Latter period Former period Latter period (mm) Immature Mature % Immature Mature % Immature Mature % Immature Mature % Female in G. eastmani <330 12 0 0 4 0 0 1 0 0 0 0 – -340 2 0 0 2 0 0 0 0 – 0 0 – -350 3 0 0 3 2 40 1 0 0 0 0 – -360 4 1 20 2 2 50 4 0 0 2 0 0 -370 4 4 50 1 10 91 1 1 50 1 0 0 -380 1 19 95 1 16 94 0 0 – 0 5 100 -390 1 32 97 0 16 100 0 7 100 0 12 100 -400 0 26 100 0 37 100 0 3 100 1 37 97 -410 0 24 100 1 33 97 0 16 100 0 56 100 -420 0 2 100 0 17 100 0 9 100 0 47 100 420 0 1 100 0 3 100 0 9 100 0 79 100 Male in G. eastmani <320 5 0 0 0 0 – 0 0 – 0 0 – -330 1 1 50 0 0 – 0 0 – 0 0 – -340 0 8 100 1 0 0 0 0 – 0 0 – -350 0 2 100 1 5 83 0 0 – 0 0 – -360 0 10 100 1 15 94 0 3 100 0 7 100 -370 0 7 100 0 7 100 0 8 100 0 15 100 370 0 2 100 0 3 100 0 10 100 0 41 100 G. nipponensis <500 72 0 0 20 0 0 100 0 0 42 0 0 -520 13 0 0 1 0 0 12 3 20 7 0 0 -540 8 0 0 0 0 – 9 1 10 11 0 0 -560 7 1 13 2 0 0 9 6 40 12 2 14 -580 9 7 44 0 3 100 0 8 100 6 9 60 -600 8 20 71 1 13 93 0 14 100 1 33 97 -620 0 37 100 0 31 100 0 6 100 0 48 100 620 0 48 100 0 47 100 0 6 100 0 25 100

% Indicates the rate of mature sharks in the class.

yellow and contained yolk material. Diameter of the class interval of 560–580 mm TL were mature. The per- maximum ovum in each mature female ranged from centage of mature females in the class interval of 10 mm to 25 mm and that of female with egg cases ranged 580–600 mm TL was 93%. Maturity size of females from 11 mm to 25 mm (Fig. 3). during the former period tended to be a little larger than The shell gland began to develop at about 480 mm TL during the latter. (Fig. 4). The ovary began to develop at about 560 mm In male sharks, the claspers began to extend rapidly TL after the development of the shell gland. Individuals at about 470 mm TL, and most claspers over 90 mm long with the shell gland over 14 mm in width and the ovary were hardened and calcified (Fig. 5). The calcified over about 25 g attained maturity. These individuals pos- claspers were observed in individuals over 490 mm TL. sessed thickened oviducts. Testes weight also began to increase at about 500mm TL. During the former period, the minimum mature size Most males over 570 mm TL possessed a pair of testes of female was 556 mm TL and the maximum immature above 5 g. Individuals with a pair of testes above 4 g and size was 598 mm TL. The percentage of mature females calcified clasper over 90 mm long attained maturity. in the class interval of 580–600 mm TL exceeded over During the former period, the minimum mature size 70%, although those in the 560–580 mm TL was 44%. of males was 514 mm TL, and the maximum immature During the latter period, the minimum mature size of size was 549 mm TL. The percentage of mature males female was 567 mm TL, and the maximum immature size in the class interval of 540–560 mm TL was 40% and was 585 mm TL. Two females in the class interval of eight individuals in the 560–580 mm TL were all mature. 540–560 mm TL were immature and three females in the In the latter period, the minimum mature size of males Reproduction and food habits of sawtail catsharks FISHERIES SCIENCE 817

Table4 Frequency of occurrence of mature individuals with egg cases by month in Galeus eastmani and G. nipponensis G. eastmani G. East West nipponensis F(%) nF(%) nF(%) n September 0 13 – – 5.9 17 October 6.5 93 10.2 59 10.7 28 November 5.0 20 0 3 18.2 33 December 9.1 11 0 9 36.4 22 January 16.7 12 – – 41.7 12 February 0 6 5.7 35 9.1 11 March 0 17 0 4 7.1 14 April 0 32 6.8 148 20.6 34 May 0 44 0 23 10.8 37

F(%), percentage by frequency of occurrence; n, total number of mature individuals in each month.

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. Fig. 5 Relationships of total length to clasper length and testes weight in Galeus eastmani from the (a) east and (b) west Main food items were Osteichthyes, Cephalopoda, and (c) G. nipponensis. (), Calcified clasper; (), soft and not and Crustacea in both sexes and both locations (Table calcified clasper; (+), testes. 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 was 546 mm TL, and the maximum immature size was were vegetable, vinyl etc. They preyed on schooling 583 mm TL. The percentage of mature males in the class pelagic species such as Engraulis japonicus. These foods interval of 540–560 mm TL was 14% and that in the were mostly observed as pieces of fish meat. The number 560–580 mm TL was 60%. Maturity size of males in the of prey species below the family level found in the female former period was a little smaller than in the latter. and male specimens in the east was at least 5 and 0 in Monthly changes of the maximum ovum diameter in Osteichthyes, 4 and 3 in Cephalopoda, and 21 and 6 in mature individuals indicated a similar tendency to G. Crustacea, respectively. The number in the west was also eastmani, as large yolky ova were found almost every 3 and 0 in Osteichthyes, 6 and 3 in Cephalopoda, and month (Fig. 6). Individuals with egg cases in the oviduct 19 and 17 in Crustacea, respectively. Females preyed on appeared every examined month (Table4). The highest more various species than males in both locations, espe- occurrence of egg cases was 41.7% in January, and the cially for Crustacea. Both females and males from the second highest was 36.4% in December. 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 Food habits males. In the west, females and males fed on more Crus- tacea and Cephalopoda than Osteichthyes. However, as Galeus eastmani shown in the parentheses of Table5, when the 120 females and 27 males collected from the west from only There were no significant seasonal differences in the one survey day in April 1996 were excluded from the index of stomach fullness (ISF) (Fig. 7). The median of total sample, the %F and %W of Osteichthyes became ISF for females from the east in each month ranged from 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 () and west () and G. nipponensis (). Symbols and extent bars indicate median and range.

east. Crustacea in the west showed higher values over Galeus nipponensis 50% in %W than in the east. In females and males from the east, there were no sig- There were no signiﬁcant seasonal differences in ISF niﬁcant seasonal differences in RI (Fig. 8). Osteichthyes (Fig. 7). The median of ISF for young and immature and Crustacea indicated higher RI over 2100 throughout females in each month ranged from 1.6% to 4.5% and three seasons, respectively. for males from 3.0% to 6.1%. The maximum ISF over 10 Females from the west had seasonal changes in RI. was observed in October, November and January for Osteichthyes indicated the highest RI of 6058 in females, and in September, October, March and April for autumn. The RI of Cephalopoda in spring showed the males. The median of ISF for mature females in each highest value of 2294. Crustacea indicated the highest month ranged from 1.1% to 4.6% and for males from RI of 6852 in spring. As noted above, we collected many 2.5% to 4.9%. The maximum ISF over 10 was observed specimens from only one survey day in April 1996. in April for females, and in September, November and Among them, 116 females had fed on a total of 5924 February for males. Only one female and one male had Euphausiacea (375 g) and 48 females also fed on Watase- an empty stomach. nia scintillans (114.8 g). Cephalopoda caught in spring, Main food items were Osteichthyes, Cephalopoda when excluded from the above specimens, indicated a and Crustacea in both sexes (Table5). Sharks preyed lower RI of 41. Males from the west also indicated sea- mainly on Osteichthyes (Sardinops melanostictus, Glos- sonal changes in RI. Osteichthyes indicated the highest sandon semifasciatus, Chlorophthalmus albatrossis and RI of 3561 in autumn. Crustacea in winter and spring Myctophidae spp.), Cephalopoda (Sepiolidae spp. and indicated a higher RI of 8596 and 8032, respectively. Enoploteuthidae spp.) and Crustacea (Aegidae spp., Cephalopoda in spring indicated the highest RI of 1491. Euphausiacea spp. and Decapoda spp.). They preyed on However, among the specimens in spring, 26 males col- schooling pelagic species such as Sardinops melanostictus, lected in April 1996 fed on a total of 732 Euphausiacea Engraulis japonicus, Carangidae spp. and Scombridae spp. (42 g), and 25 males also fed on Cephalopoda (15 g). The These foods were found to be in pieces as for G. east- RI of Cephalopoda became 0 in spring, excluding the 27 mani. The number of prey species below the family level males. found in the female and male specimens was at least 16 Reproduction and food habits of sawtail catsharks FISHERIES SCIENCE 819

Fig. 8 Seasonal changes of ranking index of foods in (a) Fig. 7 Monthly changes of index of stomach fullness (ISF) female and (b) male of Galeus eastmani from the east and west for Galeus eastmani in the (a) east and (b) west and (c) imma- of Suruga Bay. Osteichthyes in the east () and the west (); ture including young and (d) mature G. nipponensis. (), Cephalopoda in the east () and the west (); Crustacea Female; (¥), male. Symbols and extent bars indicate median in the east () and the west (). Symbols in parentheses and range. indicate the values without specimens in April 1996.

and 23 in Osteichthyes, seven and 11 in Cephalopoda, The young males had seasonal changes in RI. Oste- and 16 and 19 in Crustacea, respectively. Males tended ichthyes indicated higher RI over 1900 throughout to prey on more various species than females. Oste- three seasons. Crustacea indicated the highest RI of ichthyes indicated high %W over 60% in both female 5287 in winter. Cephalopoda indicated the highest RI of and male. The %W of Cephalopoda in females was 2915 in spring. Food items of the highest RI in autumn, higher than that of Crustacea. However, this relation- winter and spring changed in Osteichthyes, Crustacea ship was reversed in males. Non-food items appeared in and Cephalopoda, respectively. In immature males, about 30% of both females and males. there were no significant seasonal differences in RI. The young females indicated seasonal changes in RI Osteichthyes indicated the highest RI of over 6400 (Fig. 9). Osteichthyes showed the highest RI of 7319 in throughout three seasons. In mature males, the RI of autumn. However, RI of Osteichthyes in winter and Osteichthyes indicated a similar tendency as immature spring were low. Crustacea in winter and spring indicated males and mature females. Thus, young sharks in both a high RI of 4235 and 5614, respectively. In mature sexes changed food items seasonally as did G. eastmani females there were no significant seasonal differences in from the west. However, immature and mature sharks, RI. Osteichthyes indicated a high RI over 4700 through- which were of a larger size than G. eastmani, always out three seasons. preyed on Osteichthyes principally. 820 FISHERIES SCIENCE T Horie and S Tanaka and Wn % Male 0.60.6 0.20.6 0.20.6 0.2 1 0.11.3 1 0.6 1 2.21.9 1 1.00.6 1.3 2 0.4 1 3 1 0.6 0.10.6 0.6 1 0.61.3 1 0.2 0.0 1 2 1.9 0.65.8 3 2.6 13 0.6 0.20.6 4 0.1 1 % F 92.9 18.8 Galeus eastmani G. nipponensis Wn % Female 1.41.4 0.11.4 1.1 0.4 1 1 0.6 1 0.022.9 0.6 4.7 0.5 1 3 2 1.4 0.2 1 1.4 0.81.41.4 0.1 1 0.4 1.3 1 0.2 1 2 5.7 3.2 8 16.9 3.5 37 4.3 5.6 3 3.2 6.11.4 0.5 5 1.4 10.05.7 1 8.21.4 3.2 1 1.4 4.0 19 0.4 1.3 12.3 10.5 1 5 1 1.3 37 0.1 2 4.3 2.3 3 2.6 3.5 5 7.3 % F Wn % West n ) in each food item for female and male of Male % F Wn % East % F 84.6 21.5 40.9 (64.7) 1.4 (12.2) W ) and number of individuals ( G. eastmani 8 1 Wn % West ), percentage by weight (% F Female % F 0.6 (2.9) 0.4 (3.9) 1 (1) 0.6 0.1 Wn % East 3.5 2.81.7 4 4.70.9 2 0.3 0.6 (2.9) 1 1.8 (19.1) 1 (1) % F sp. spp. sp. sp. Percentage by frequency of occurrence (% evermanni scolopax melanostictus semifasciatus albatrossis unit Peristedion orientale Carangidae spp. Decarterus tabl Cepola schlegeli Champsodon snyderi Foetorepus Benthodesmus tenuis Scombridae spp. Paralichthydae sp. Pleuronectidae spp. kitaharai Tanakius Osteichthyes spp. 87.0 17.9 59.7 (85.3) 1.7 (8.1) Hygophum Symbolophorus Diaphus garmani Chaunax abei Zenion japonicum Macroramphosus Scorpaenidae sp. sp. Triglidae Lepidotrigla Benthosema pterotum Osteichthyes spp.Anguilliformes spp. Sardinops 40.9 8.9Engraulis japonicus Euteleostei spp. 81Glossanodon 20.1 (23.5) 2.5 (12.8)Stomiiformes spp. 1.7Maurolicus muelleri 39 (13) 0.5Sternoptychinae sp. 19.2Polyipnus stereope 0.9 2Phosichthyidae sp. 6.7 11Chlorophthalmus 0.6 (2.9) 0.7 13.6 (5.9)Neoscopelidae spp. 1 0.1 (1.5) 0.8 (0.5)Neoscopelus Myctophidae spp. 7 (2) 1 (1) 61.4 6.1 3.8 11.1 6.2 3.1 127 26.0 1 7 10.6 4.5 (5.9) 4.5 1.0 (8.9) 84 2 (1) 1.5 2.9 0.4 2 5.8 0.9 12 Total of OsteichthyesTotal 88.7 41.9 98 64.9 (85.3) 8.1 (45.3) 51 (16) 84.6 31.3 12 45.5 (64.7) 3.1 (21.5) 9 (3) 88.6 61.8 176 94.2 65.1 229 Table5 G. nipponensis Reproduction and food habits of sawtail catsharks FISHERIES SCIENCE 821 % Wn Male 0.6 0.02 1 1.9 0.41.9 0.3 3 3 0.6 0.2 1 0.6 0.010.6 4.2 1 1 1.3 0.1 2 3.2 0.02 6 0.60.6 0.12.6 0.4 0.2 1 0.6 1 4 0.13.9 1.3 1 6 % F G. nipponensis % Wn Female 1.4 1.3 1 1.3 0.5 2 1.4 3.8 1 2.91.4 0.1 0.003 2 1 1.9 0.03 4 5.7 1.71.4 0.02 4 8.4 1 2.7 1.3 0.02 13 2 % F 11.4 0.8 12 7.8 0.2 16 37.1 3.4 47.4 2.6 1 4.3 0.5 4 3.2 0.01 6 % Wn West Male % F 4.5 4.0 2 1.4 1.8 6 10.4 3.7 28 2.36.8 0.9 3.4 1 3 2.9 0.6 5 6.5 0.7 12 2.3 (5.88) 0.04 (0.4) 1 (1) 1.4 0.8 1 1.9 0.2 3 % Wn East 3.8 0.1 1 % F 23.1 7.7 13 63.9 (23.5) 8.9 (0.9) G. eastmani 1 23 11.5 3.8 6 2 2 % Wn West Female % F 0.6 (2.9) 0.001 (0.01) 1 (1) 0.6 0.1 5.2 0.05 8 3.8 0.4 1 1.3 0.1 % Wn East 7.8 1.3 9 1.90.9 0.2 0.1 1 2.6 2.3 3 4.3 0.2 5 0.6 0.02 1 3.8 0.3 1 0.9 0.1 1 20.1 (8.8) 2.6 (0.2) 42 (7) 4.5 3.3 3 4.3 0.8 4 0.6 0.03 1 2.6 2.4 3 0.64.3 6.1 0.3 5 31.2 14.1 60 % F Continued doederleini curvirostris beak beak beak bartrami unit spp. beak Argathona japonica Aegidae spp.Aega antillensis Rocinela maculata Amphipoda spp. 17.4Gammaridae spp.Euphausiacea spp. 2.5 20.0Decapoda spp. 0.9 23 13.0Haliporoides sibogae 1.0Aristeidae sp. 0.1 0.6 0.9 45Trachypenaeus 53.9 10.4 50 2 6.8 85.1 (35.3) 154 46.4 (4.8) 0.1 35.7 (38.2) 5980 (56) 0.2 3.0 (7.9) 7.7 1.4 84 (25) 6 23.1 26 68.2 10.2 8 34.1 (52.9) 19.2 57.9 6.1 (14.0) 1.3 23 (11) 7 34.3 20.5 (29.4) 741 4.9 0.6 (5.3) 12 (6) 88 4.3 42.9 0.4 1.9 27 154 8.4 0.2 43 Onychoteuthidae sp. Gonatidae spp. beak Histioteuthidae spp. Ommastrephidae sp. Ommastrephes Octopoda spp.Cephalopoda spp. 40.0 1.7 5.0 0.6Bathynomus 2 81.2 (41.2) 1.3 5.2 (1.1) 0.01 2 Cirolana japonensis Sergestes lucens Cephalopoda spp. Coleoidea spp.Sepiidae sp. Sepiadarium kochii Sepiolidae spp. 3.5Sepiolidae spp. beakSepiolina nipponensis 4.2 7.8Loliginidae spp. 1.7Loliginidae spp. beak 0.1 4Enoploteuthidae 0.5 9.1 13 14.3Enoploteuthidae spp. 2 13.9 0.9 2.6 (5.9) scintillans Watasenia 0.4 0.7 2.8 0.4 (0.04) 0.1 25 1 56.5 (17.6) 4 (2) 0.5 (0.4) 17 27 261 (7) 11.5 0.2 7.7 3 0.2 31.8 2 2.3 0.5 0.02 31 7.1 0.1 14 20.1 0.04 53 Total of CrustaceaTotal 92.2 28.7 380 92.9 (73.5) 67.3 (51.0) 6261 (101) 76.9 27.3 36 93.2 (82.4) 78.8 (68.7) 795 (29) 67.1 17.7 172 66.2 9.7 283 Table5 Total of CephalopodaTotal 55.7 19.7 55 86.4 (55.9) 23.4 (1.5) 384 (10) 42.3 8.5 19 65.9 (23.5) 17.7 (5.7) 39 (1) 51.4 9.0 38 60.4 16.6 137 822 FISHERIES SCIENCE T Horie and S Tanaka Wn % Male 0.60.6 0.001 0.031.3 1 0.004 1 0.6 2.7 1 3.9 0.10.6 0.1 6 1 0.60.6 0.1 0.1 1 1 % F G. nipponensis Wn % Female 4.35.7 0.2 1.7 31.4 8 0.6 0.04 2.6 0.01 0.1 1 1 5 2.9 0.2 2 1.4 0.1 1 0.6 0.1 1 2.9 0.61.4 0.5 2 1 1.3 0.5 2 2.9 0.03 2 1.3 0.1 2 1.4 0.2 1 5.7 1.5 5 3.2 0.3 5 1.4 0.042.9 0.1 1 0.6 4 0.01 3.9 1 0.2 70 599.3 154 1576 % F 34.3 11.3 29.2 9.0 25.7 1.4 26.0 1.0 Wn % West Male % F 2.3 0.2 1 6.8 3.2 3 2.3 (5.9) 0.3 (3.6) 1 (1) 2.3 (5.9) 1.9 (20.7) 2 (2) 5.7 0.7 4 11.7 0.7 18 Wn % East 3.8 0.5 1 2.3 0.1 1 1.4 0.003 1 7.7 1.4 6.8 (11.8) 1.0 (8.5) 26 12.8 44 (17) 81.9 (7.57) % F 26.9 32.2 38.5 3.8 22.7 (35.3) 2.1 (11.4) G. eastmani 4 1 3 Wn % West Female % F 0.6 (2.9) 0.1 (1.0) 1 (1) 1.9 (2.9) 0.3 (0.7) 3 (1) 0.6 (2.9) 0.03 (0.3) 2 (2) 0.6 (2.9) 0.2 (1.8) 1 (1) 0.6 (2.9) 2.6 (27.1) 1 (1) 1.9 1.0 24.7 6.1 69 Wn % East 5.2 1.3 5 7.1 (0.1) 0.2 (0.7) 11 (2) 3.8 0.7 1 2.3 (5.9) 0.4 (4.1) 1 (1) 1.4 0.1 1 5.2 0.5 6 0.9 0.10.9 1 0.1 1 1.7 0.4 2 1.7 0.2 3 0.6 (2.9) 0.02 (0.2) 1 (1) 0.9 0.1 1 0.9 1.9 1 0.6 (2.9) 0.2 (2.0) 1 (1) 0.9 0.2 1 % F 115 261.4 154 (34) 815.4 (77.9) 11.3 1.1 19 12.2 2.8 17 6.5 (5.9) 0.8 (1.7) 10 (2) spp. Continued dofleini monstrosus gracilirostris Holothroidea sp. Polychaeta spp.Polychaeta spp. unit 0.9 2.6 0.02 0.9 3 0.6 5.8 (5.9) 0.2 (0.7) 0.002 11 (2) 3.8 0.7 1 2.3 (5.9) 0.4 (4.1) 1 (1) 1.4 0.1 1 2.6 0.4 4 Amphinomidae sp.Ophiuroidea spp. 0.9 0.3 0.9 0.02 1 1specimens and 1.3weight, g) 0.01 2 Oplophoridae spp. Megalopa Dorippidae sp. Goneplax renoculis Pseudosquilla ciliata Pseudosquillopsis Squillidae sp.Squilloides leptosquilaa Brachyura spp. unitCrustacea spp. unit 13.0 0.9 39.1 1.1 0.02 2.2 1 0.6 (2.9) 4.5 (5.9) 29.9 (17.6) 0.001 (0.01) 0.3 (0.6) 1.7 (2.4) 1 (1) Scyllarides squamosus Diogenidae spp.Axiidae spp. Parapagurus 4.3Galatheidae sp. 0.7Munida japonica Brachyura spp. 5 0.9 1.9 0.02 2.6 1 0.5 0.2 3 0.6 0.0 Scyllarus cultrifer Crangonidae spp.Crangon sagamiensis Nephropidae sp. 11.3Nephropsis stewarti 1.5Polycheles typhlops Palinuridae sp. 19Scyllaridae spp. 7.1 0.9 8.7 0.1 1.2 0.4 1 11 1.9 (2.9) 20 0.1 (0.3) 11.5 4 (2) 3.6 3.8 5 11.4 0.9 1 2.0 8 4.3 0.1 3 4.5 0.1 7 Plesionika martia Heterocarpus Systellaspis debilis Plesionika grandis Heterocarpus sibogae Oplophorus Value in parentheses excluded specimens April 1996. Value Total (No. of Total Non-food items 37.4 8.4 13 (23.5) 0.9 (1.5) Other Table5 Reproduction and food habits of sawtail catsharks FISHERIES SCIENCE 823

Fig. 10 Monthly changes of water temperature by depth Fig. 9 Seasonal changes of ranking index of foods in (a) during the former (1981–1989) and the latter (1992–1996) young, (b) immature and (c) mature of female and male Galeus periods in the (a) east side and (b) west side of Suruga Bay nipponensis. Osteichthyes in female () and male (); (from Fisheries Experiment Station of Shizuoka11–13). 150 m in Cephalopoda in female () and male (); Crustacea in female depth during the former period () and the latter (); 200 m () and male (). in depth during the former period () and the latter (); 250 m in depth during the former period () and the latter (); 300 m in depth during the former period () and the DISCUSSION latter ( ).

The ovum was considered to be ovulated between 18– 20 mm in G. eastmani and between 20–25 mm in G. nip- the former and latter periods. Namely, those in April and ponensis. Both species of Galeus with egg cases had yolky May during the latter period were higher by about 1°C ova over 8 mm in diameter. The interval of laying egg than during the former period (Fig. 10).11–13 Size at sexual cases in Scyliorhinus retifer ranged from 14.1 to 16.7 days maturity of Mustelus manazo tended to become larger for the mean rate.10 Large yolky ova of both species of with the decline in water temperature.14 The change of Galeus with egg cases would be ovulated again after a few maturity size in both species may be caused by the change weeks. of physical environments. However, further investiga- Size at sexual maturity of both species of Galeus dif- tion of both biological and environmental information fered between the former and latter periods. It is gener- is needed to elucidate the variation. Female G. eastmani, ally known that size at sexual maturity in ﬁshes changes collected off Kochi, possessed a fully developed ovary and according to the population size and environmental shell gland over 368 mm TL, and female G. nipponensis conditions. In Suruga Bay, the monthly average of water also had fully mature gonads over 556 mm TL.1 The temperature at every 50 m in depth from 150 to 300 m, minimum size of mature individuals in female G. east- where both species of Galeus inhabit, differed between mani in the west and female G. nipponensis in Suruga Bay 824 FISHERIES SCIENCE T Horie and S Tanaka

was almost the same as the size at sexual maturity in both pieces of pelagic fishes, which were already cut off, in the species from Kochi. same way as non-food items. It is unknown how the For G. eastmani, size at sexual maturity differed pieces are derived. between the east and west of Suruga Bay. Distance Both species preyed on various organisms. Galeus between the east and west fishing grounds was only about melastomus from the western Mediterranean also fed on 10 km. However, there is the Suruga Trough reaching a wide variety of prey, and their foods differed by depth over 2000 m deep between both fishing grounds, and no for a change in available food resources.19 Galeus polli and G. eastmani were fished in the innermost recesses of five species of Scyliorhinidae from the west coast of Suruga Bay. The CPUE of G. nipponensis differed a great southern Africa preyed mainly on Osteichthyes.20 Galeus deal between both locations which may indicate a rare eastmani in the east preyed mainly on Osteichthyes and interchange of populations between the east and west. Crustacea throughout three seasons. In contrast, G. east- Both species of Galeus tended to ovulate throughout mani in the west preyed mainly on Crustacea in winter the year. Occurrence of egg cases in G. eastmani from the and spring seasons. Galeus eastmani, caught in April 1996 east showed a bias by month. Galeus nipponensis possessed from the west, foraged much more Cephalopoda (espe- egg cases in all examined months, and they indicated cially Watasenia scintillans) and Crustacea (especially the higher occurrence rate in December and January. Euphausiacea spp.). Watasenia scintillans seems to have Scyliorhinus canicula, belonging to Scyliorhinidae as aggregated for preying on Euphausiacea spp. Thus, G. Galeus, from the Menai Straits and the Adriatic, deposits eastmani also may eat different types of prey between egg cases throughout the year with maximum intensity locations for a change in available food resources. Imma- in spring and a minimum in the fall.15,16 In S. canicula, ture and mature specimens of G. nipponensis were pri- maximum feeding intensity lags behind or precedes the marily piscivorous throughout three seasons. However, most intensive spawning periods.16 Thus, S. canicula has the young of G. nipponensis differed in their foods the most intensive spawning periods in spite of ovulat- between seasons, and preyed on different foods from G. ing all year round. This may be caused by an interval of eastmani in the same location. The young of G. nippo- egg cases deposition. Interval of egg cases deposition in nensis also preyed on various organisms. These may indi- Scyliorhinus retifer ranged from 14.1 to 16.7 days for the cate that G. eastmani and the young of G. nipponensis mean rate and changed in water temperature.10 Galeus change prey items to avoid food competition between sauteri inhabits the bottom layer where water tempera- them. We have concluded from the diet composition ture remains constant throughout the year, and it is that both species are voracious and opportunistic feeders. 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 ACKNOWLEDGMENTS examined years indicated a lower value from August to September and a higher value from October to January, We are grateful to Dr GM Cailliet, Moss Landing Marine and the difference between the higher and lower tem- Laboratories, for his review and linguistic correction of 11–13 peratures was about 2°C (Fig. 10). Thus, water tem- the first draft. We also thank Katsumi Yamada, captain perature in Suruga Bay showed little fluctuation through of the trawl boat Hinode maru, and the crew for their help the year. Therefore, both species may have a bias in with sample collection. 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. REFERENCES Cephaloscyllium umbratile from Choshi, Japan also preyed 1. Nakaya K. Taxonomy, comparative anatomy and phylogeny of frequently on schooling pelagic species such as sardine Japanese catsharks, Scyliorhinidae. Mem. Fac. Fish. Hokkaido 6 and mackerel. Scyliorhinus canicula is known to be Univ. 1975; 23: 1–94. nocturnally active.18 Compagno8 hypothesized that the 2. Tachikawa H, Taniuchi T. Galeus longirostris, a new species of the nocturnal activity pattern of the sluggish and weak- sawtail catshark from Japan. Jpn. J. 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