SUISANZOSHOKU 47(3), 331-336 (1999)

Food and Feeding Habits of the Japanese , japonica, in Tateyama Bay

SULIsTIONO * 1, Seiichi WATANABE * 1, and Masashi YOKOTA * 1

(Accepted May 19, 1999)

Abstract: The study on food and feeding habit of the , Sillago japonica, were conducted. Stomach contents were examined from 442 (varied from 115 mm to 245 mm total body length) collected using encircling trammel net from October 1993 to January 1995 in Tateyama Bay. All samples were distinguished to be male (n=227) and female (n=215). Monthly changes on the index of stomach contents (ISC) indicated that feeding became active from April (0.39) to September (0.45) and decreased during October to March. Four phyla of organisms were found in the stomach of the samples, which were Arthropoda, Mollusca, Annelida and Chordata. Major diets of fish were Natantia () and Polychaeta which constituted of 44% and 33% in female and 40% and 34% in male, respectively. Stomach contents of male and female were similar. They varied according to the sampling month and season. The feeding incidence on Natantia increased corresponding to size in both female and male.

Key words: Sillago japonica; Food and feeding habits; Tateyama Bay

One of the most popular fish in Japan, the and feeding habits of S. japonica in Tateyama Bay. Japanese whiting, Sillago japonica, is commonly

consumed, and also a target for game fishing in Materials and Methods sandy coastal areas, especially during the summer

season. It is distributed along the from Samples were taken monthly by encircling

Hokkaido to Kagoshima in Japan, , , trammel net in Tateyama Bay (139•‹49'-139•‹51'E

Taiwan and probably also Philippines1). Over- and 34•‹59'-35•‹01') from October 1993 to January fishing and the degradation may have 1995. A total number of 442 fish were collected.

caused a decline in some populations. Total length-TL (nearest 1 mm), total body

Although several studies on ecology2,3), weight-BW and stomach content weight-SCW fishing methods4) and a number of experimental (nearest 0.01 g) were measured. After the observations5-12) have been conducted on S. stomach was dissected out, its contents were japonica, little information on food and feeding preserved in 10% formalin. These stomach habits of this has been available. Observa- contents were later removed into a petri dish tions on the food and feeding habits of Sillago and observed under a stereo microscope and japonica in Hiroshima, Japan13) revealed that it identified14-19). mainly feeds on and . Index of stomach contents was computed using

To understand of the interaction between mem- ISC =102 SCW/BW14,20) Frequency of occurr- bers of a community and prey selection which ence in stomach contents was determined20)

enables mapping of energy, nutrient, and occa- Similarity index analyses were carried out on the

sionally pollutant flow and management of natural prey to compare differences between female and populations and , we investigated food male and among seasons; the equation used

* 1 Tokyo University of , Department of Aquatic Biosciences, 4-5-7 Konan, Minato, Tokyo 108-8477, Japan. 332 Sulistiono, S. watanabe, and M. Yokota was, similarity index S = 2C/(A+B), where A, B = number of different prey items in groups A and B, C = number of joint prey items shared by groups A and B20).

Results

Fish Length Composition Samples of 442 individual of fish were disting- uished to be female and male. The total length distribution of both sexes are presented in Fig. 1. All samples were adult, ranged from

135 to 245 mm in females and from 115 to Fig. 2. Monthly changes of the index of stomach contents 245 mm in males. This figure also shows that of the Japanese whiting, Sillago japonica, collected there exists more than one modes, 165 mm and from Tateyama Bay. Vertical bars indicate standard 195 mm in female and 155 mm, 185 mm and deviation. 215 mm in male. around 0. 39, increased to 0.57 in June and 0.59 Feeding Activity in August, but it decreased in October to March, Feeding activity of S. japonica collected in when the ISC values were 0.30 (October), 0.04 Tateyama Bay from April to September using (December) and 0. 12 (March). analysis of index of stomach content (ISC) is presented in Fig. 2. In April the value was Stomach Contentsprey Prey types in the stomach contents were represented by at least 9 orders in 4 phyla: Arthropoda (Crustacea): Mysidacea, Tanaedacea, Isopoda, , Decapoda (Natantia, Brachyura), Stomatopoda; Mollusca (Gastropo- da); Annelida (Polychaeta); Chordata (Osteich- thyes). Major ones were Crustacea (33%, 34%), and Polychaeta (44%, 40%), for female and male respectively (Fig. 3). The figure shows that prey types of female and male Japanese whiting were similar. A similarity index of 85% (with 11 organisms was found in both female and male; 11 in female and 15 in male) showed that the diet was basically the same between sexes. However, prey types in male seemed more varied as Mycidacea, Tanaedacea and Stomatopoda were not found in female. Unidentified flora (debris), fauna, and inert matter (silt) were also found in the stomach contents.

Relationship betweenStomach Contents and Season Monthly observation on the stomach contents of both female and male fish is presented in Fig. 4. Fig. 1. Total length frequency distribution of the Japanese From these results, it can be stated that the diet of whiting, Sillago japonica, collected in Tateyama Bay. both sexes were similar. As shrimps (Natantia) Food and Feeding Habits of Sillago japonica 333

Fig. 3. Diet composition of the stomach contents of the Japanese whiting, Sillago japonica, collected from Tateyama Bay. C-Crustacea: A-Amphipoda, B-Brachyura, I-Isopoda, M-Mysidacea, N-Natantia, S-Stomatopoda, T-Taenadacea; Mollusca: G-Gastropoda; Annelida: P-Polychaeta; : O-Osteichthyes; D-Debris; Si-Silt; U-Unidentified .

Fig. 4. Monthly stomach contents of the Japanese whiting, Sillago japonica (with number of samples), collected in Tateyama Bay. C-Crustacea: A-Amphipoda, B-Brachyura, I-Isopoda, M-Mysidacea, N- Natantia, S-Stomatopoda, T-Taenadacea; G-Gastropoda; O-Osteichthyes; P-Polychaeta; D-Debris; Si- Silt; U-Unidentified animals. 334 Sulistiono, S. watanabe, and M. Yokota

and polychaetes were always present in the Table 1. Similarity index of the diet of the Sillago japonica stomach contents of at least one sex, these prey in Tateyama Bay among seasons were always present in both feeding ground. Generally consumption of crustaceans exceeded that of polychaetes with no significant correlation to season in either sex. However, in October 1993 only around 20% of the diet was polychaetes, and none in January 1994, but from June to August 1994, it was the major diet in female. In male, it appeared that no polychaetes were consumed in November 1993, but in January 1995 it occupied around 60% of the diet. As shown in Table 1, when similarity index analysis was employed for diets among seasons by sex, the values were smallest between winter and autumn in female (0.59), and between summer and spring (0.63) in male. But highest in female (0.80) between winter and summer, and in male (0.84) between autumn and spring.

Relationship between Stomach Contents and Total Body Length Figure 5 shows the relationship between the stomach contents and total body length. Analysis of samples from a minimum size of 150 mm to 210 mm maximum (at 10 mm intervals) showed that in both sexes, fish consumed more Natantia and less Polychaeta as they grew. This figure shows the change in the food preference at around 160-175 mm in TL.

Discussion

Feeding activity of the Japanese whiting in Fig. 5. Length and diet composition of the Japanese whiting, Tateyama Bay appeared to be most active from Sillago japonica, collected from Tateyama Bay. April to October. This correlated both to the May- October spawning season and the increasing water found in male). Male included Taenadacea in their temperature. It was also close to the period of diet (not found in female), and also had more plant feeding activity of April to September reported for matter (2% debris) than female (0.4%). From the same fish in Hiroshima13). these observations, S. japonica collected in this Based on the examination, main foods of S. area was predominantly carnivorous. This condi- japonica collected in Tateyama, Crustacea (mainly tion is similar to that in whiting from the Seto Natantia) and Annelida (Polychaeta) were by far Inland Sea (Hiroshima)13. Although it can be the principle prey. In total, 49.5% of stomach stated that crustaceans and polychaetes were the contents were crustaceans and 33% polychaetes preferred prey of S. japonica in Tateyama Bay, in female and 43% and 34%, respectively in male. the percentage of each consumed probably was The diet of female was more varied most dependent on the prey availability in the including , mysids, and amphipods (not feeding ground as can be seen in Kakuda's report Food and Feeding Habits of Sillago japonica 335

(ibid. ) where Macrura was the dominant crusta- process in encircling gillnet as inferred from catch. cean. Nippon Suisan Gakkaishi, 58(2), 249-254. 5) Kashiwagi, M., N. Yamada, Y. Okada, and F. Nakamura On the monthly basis as shown in Fig. 4, (1984): A periodic variation of spawning time of Japanese generally crustaceans were dominant, polychaetes whiting Sillago japonica during the spawning season. second, but in several months the reverse was Bull. Japan. Soc. Sci. Fish., 50(12), 2135. found. Why no polychaetes were consumed by 6) Kashiwagi, M., H. Sasaki, and T. Takahashi (1987): A relationship between size and hatching rate in male in November 1993 and female in January Japanese whiting Sillago japonica. Nippon Suisan 1994 can not be explained as they were present Gakkaishi, 53(12), 2105-2110. in the feeding ground, consumed in great number 7) Oozeki, Y. and R. Hirano (1985): Effects of temperature by the opposite sex. No significant trends or changes on the development of eggs of the Japanese whiting Sillago japonica Temmincki et Schlegel. Bull. correlation between prey and seasons could be Japan. Soc. Sci. fish., 51(4), 557-572. found. 8) Oozeki, Y. and R. Hirano (1986): Variation in

Although the stomach contents among seasons qualities of the Japanese whiting, Sillago japonica, in the were similar, when analyzed by similarity index spawning season, in •gFirst Asian Fisheries Forum•h (ed. by J. L. Meclean, L. B. Dizon, and L. V. Hosillos), (Table 1), it was found that it was closest in female Asian Fisheries Society, Manila, pp. 679-681. (0.59) between winter and autumn, and in male 9) Oozeki, Y. and R. Hirano (1994): Changes in oxygen (0.63) between summer and spring. This relation- consumption rate during development of larvae, ship may have been caused more by physiological Japanese whiting Sillago japonica. Japan. J. Ichthyol., 41(2), 207-214. (e.g. maturity-immaturity) and the environmental 10) Oozeki, Y., P-P Hwang, and R. Hirano (1992): Larval (e.g. prey availability) conditions than on seasonal development of the Japanese whiting, S. japonica. Japan food preference. J. Ichthyol., 39(1), 59-66. From analysis of the change in preference as 11) Kumai, H. and M. Nakamura (1977): On the natural reflected in stomach contents (Fig. 5), in both spawning of borer, Sillago sihama (Forsskal), Mem. Fac. Agric. Kinki Univ., (10), 39-43. sexes, at around 170 mm TL, prey preference 12) Kumai, H. and M. Nakamura (1978): Spawning of the switched from polychaetes to shrimps. As the fish silver whiting Sillago sihama (Forsskal) cultivated in grew, shrimps represented a larger percentage of laboratory. Bull. Japan. Soc. Sci. Fish., 44(9), 1055. 13) Kakuda, S. (1970): Studies on the ecology and fishing the diet, reaching around 80% at 210 mm TL. This stock of Sillago sihama (Forsskal) through the analysis was probably in part caused by the environmental of Its bottom drift-net . J. Fac. Fish. Ani. Hus., factors such as availability and distribution of Hiroshima Univ. , 9, 11-55. foods, but the change in prey preference was 14) Roman, R. (1985): Feeding of Aplocheilichthyes mainly related with maturity of the fish. The normani, Ahl, a small Cyprinodontidae from West . J. Fish Biol., 26, 399-410. previous study21 found that 90%-100% of the 15) Burukovskii, R. N. (1983): Key to Shrimps and Lobster. large-sized fish collected during spawning season Balkema, Rotterdam, 174 p. (June-October) were mature fish. However, a 16) Hayashi, K. (1992): Ecology and of the more detailed study on diet and the maturity is Japanese Shrimps. Dendrobranchiata Crustaceans from Japanese Waters. Seibutsu Kenkyusha, Tokyo, 300 p. needed to provide a more definite explanation. 17) Okada, M. (ed.) (1965): Illustrated Encyclopedia of the Fauna of Japan. Hokuryu-kan, Tokyo. 803 p. References 18) Dore, I. and C. Frimodt (1987): Illustrated guide to of the world. An Osprey Book, New York. 229 p. 1) Masuda, H., K. Amaoka, C. Araga, T. Uyeno, and T. 19) Nishimura, S. (1995): Guide to seashore animals of Japan Yoshino (eds.) (1984): The of the Japanese with color pictures and keys, Vol. II. Hoikusha. 663 p. Archipelago. Tokai University Press, Tokyo. 437 p. 20) Cailiet, G. M., M. S. Love, and A. W. Ebeling (1986): 2) Ito, M. and H. Uchida (1990): Age and growth of Fishes. A field and laboratory manual on their structure, Shirogisu in Chikuzen Sea. Seikaiku Block, Gyoruikenk- identification and natural history. Wadsworth Publishing yukaihou, 7, 39-44. Company. Belmonth, California, 194 p. 3) Sulistiono, M. Yokota, S. Kitada, and S. Watanabe 21) Sulistiono, S. Watanabe, and M. Yokota (1999): Repro (1999): Age and growth of Japanese whiting, Sillago duction of the Japanese whiting Sillago japonica in japonica in Tateyama Bay. Fisheries Sci., 65(1), 117- Tateyama Bay. Suisanzoshoku, 47(2), 209-214. 122. 4) Kawamura, G., S. Mori, and S. Toya (1992): Catching 336 Sulistiono, S. Watanabe, and M. Yokota

館 山 湾 に お け る シ ロ ギ ス,Sillago japonicaの 食 性

SULISTIONO・ 渡 邊 精 一 ・横 田 賢 史

館 山湾 にお いて1993年10月 か ら1995年1月 に かけ て漕 ぎ刺 網 に よ り採 集 した シロギ ス442個 体(全 長115～245mm)の 食 性 を調 査 した。標 本 は雄227個 体,雌215個 体 で あ った。 胃内容 物指 数(ISC) は4月 か ら9月 まで は高 く,10月 か ら3月 まで は低 い値 を示 した。標 本 中 には節 足動 物,軟 体 動物, 環形 動物,脊 索動 物が餌 生 物 として見 られ た。同湾 におい ては遊 泳類 と多 毛類 が本種 の主要 な餌 であ り,雌 で は それ ぞれ44%,33%,雄 で はそ れぞ れ40%,34%を 占 め てい た。雌 雄 と も胃内容 物 は類似 してお り,餌 生物 の存在 比 率 は季節 的変化 が 見 られ た。サ イズ の増加 と ともに遊 泳類 を利 用 す る割 合 が 高 くな った。