Japanese Journal of Ichthyology 魚 類 学 雑 誌 Vol.34, No.2 1987 34巻2号1987年

The Oriental Goby, Acanthogobius River system, 30km north of Sydney Harbour. flavimanus, Colonizes a Third These data were taken mostly from a study of Estuary in New South Wales, fishes associated with seagrass habitats (Bell, 1986) Australia and they indicate that A. flavimanus is re producing in the Hawkesbury system.

Johann D. Bell, Aldo S. Steffe and R. Bill Talbot Methods

(Received October 21, 1986) In June (winter) and December (summer) 1984 all fish were collected from a 36m2 plot within The oriental goby, Acanthogobius flavimanus, is each of 24 beds of the seagrass Zostera capricorni, native to estuarine and brackish waters of Japan, and in 30 of the 7m2 artificial seagrass units the Korean Peninsula and China (Masuda et al., (ASUs) described by Bell et al. (1985), distributed 1984), but it has spread elsewhere. In 1963 A. throughout the Pittwater and Cowan Creek arms of the Hawkesbury system (Fig. 1). We sampled flavimanus was collected in San Francisco Bay, fish from Zostera plots by surrounding them with and was common there by 1970 (Brittan et al., a wall net of 1mm mesh and then applying roten 1970). Individuals from San Francisco Bay reach one, after Gray and Bell (1986). We collected sexual maturity within a year and grow to 270mm fish from an ASU by completely encasing it with total length (TL) (Baker, 1975). The oriental a net of 1mm mesh and then applying rotenone goby is thought to have been introduced to San Francisco via ballast water discharged from cargo (Bell et al. 1985). ASUs were submerged for six weeks prior to collection. ships (Brittan et al., 1963). On 8 May 1985, we collected all oriental gobies Acanthogobius flavimanus has also been intro from the catch of a small (10m L.O.A.) commercial duced to Australia, presumably in ballast water prawn trawler, operating further up the Hawkesbu (Hoese, 1973). Between 1971 and 1981, 107 spec ry River from our sites (Fig. 1). The -trawl used imens, comprising mostly adults, were collected had a minimum mesh size of 38mm, and so was from Sydney Harbour and Botany Bay, 20km only capable of catching adult gobies. to the south. Except for two specimens from All oriental gobies collected were preserved in the Hunter River, a major port 120km north of 10% formalin and later measured to the nearest Sydney, there are no records of the goby from millimetre TL. other Australian estuaries (Middleton, 1982; J. Paxton, pers. comm.). This is in contrast to the Results and discussion distribution of another introduced goby, Tri dentiger trigonocephalus, in Australia: it has been- No oriental gobies were collected in June 1984. recorded from Sydney Harbour, Port Kembla, In contrast, we collected 72 gobies in December Melbourne and Perth (Paxton and Hoese, 1985; 1984; 50 from nine Zostera sites and 22 from six R. Talbot, unpublished data). ASUs (Fig. 1). All of these gobies came from Ninety-six of the specimens of A. flavimanus sites in Cowan Creek. Specimens ranged in length from Sydney Harbour and Botany Bay were ex from 38-73mm; their mean length was 58.4mm•} amined by Middleton (1982). Although the spec 7.6 S.D. Individuals of this length in San Fran imens included sexually mature females, Mid cisco Bay are in the 0+age class (Baker, 1975).- dleton was not sure whether the gobies were The 16 specimens from the prawn trawler ranged spawning or whether catches represented indi in length from 118-200mm and had a mean viduals from continual introductions in ballast length of 167.4mm•}22.4 S.D. Individuals of water. However, a collection of running ripe in this size are sexually mature (Baker, 1975; Mid dividuals from Sydney Harbour in 1983 (P. Gibbs, dleton, 1982). pers. comm.) indicates that A. flavimanus is spawn Three events could explain absence of oriental ing there. gobies in Cowan Creek during June and the rel Here we report data from an estuary that is not ative abundance of 0+aged individuals the fol a port for ocean-going vessels, the Hawkesbury lowing December. First, as larvae of A. flavimanus -

―227― 魚類学雑誌 Japan. J. Ichthyol. 34 (2), 1987

Fig. 1. Map showing location of Zostera sites (•œ) and artificial seagrass units (•›) in Pittwater and Cowan Creek. Also shown is the general area where adult gobies were collected within the Hawkesbury River itself. Numbers are abundances of 0+ aged oriental gobies collected at that

site.

―228― Bell et al.: Gobiid Record from Australia are pelagic (Dotu and Mito, 1955), larval recruits duced to Australia, Tridentiger trigonocephalus, could have arrived in ballast water dumped in was living in the water intake pipe of a local trawler

Sydney Harbour or Botany Bay between June and moored in Sydney Harbour (Paxton and Hoese, December. Second, as A. flavimanus is a winter 1985). spawner (Dotu and Mito, 1955), larvae spawned It took 13 years, from the first record of A. in Sydney Harbour or Botany Bay could have dis flavimanus in Sydney Harbour in 1971 (Hoese, persed northwards to colonise the Hawkesbury- 1973) to the apparent establishment of a breeding system by December. Third, adults are already population in an estuary •`30km to the north. established and spawning in the Hawkesbury It is possible that the spawning biology and pat system, with juveniles recruiting to habitats in the terns of water discharge from estuaries in N.S.W. lower reaches during December and then moving may slow the rate of further larval dispersal of from these to the more brackish spawning habitat A. flavimanus. The adult specimens from the up the river before the end of their first year (i.e. Hawkesbury River, and the ripe fish collected

June). from Sydney Harbour by P. Gibbs, were taken Larval gobies recruiting from sites for disposal 15-20km from the sea. Spawning during winter of ballast water, or from spawning sites in Sydney in such locations, and the demersal nature of the

Harbour and Botany Bay, should settle in Pitt eggs (Dotu and Mito, 1955), places larvae well water, as well as in Cowan Creek because both inside estuaries when river flow rates are at a areas receive oceanic water during flood tide (A. minimum (Bureau of Meteorology, 1979). Thus,

Nielsen, pers. comm.). Since no gobies occurred larvae of A. flavimanus have a high probability of in Pittwater during our comprehensive collections, being retained within their natal estuary. Never the first and second propositions are unlikely to theless, we believe the oriental goby will colonize explain the appearance of relatively high numbers other estuaries on the coast of N.S.W. in a slow of 0+ individuals in the Hawkesbury system. and stepwise manner. This will happen at a faster The presence of fish of breeding size upcurrent rate to the north of Sydney because surface cur from Cowan Creek suggests that the gobies we rents within 1km of the coast usually move in collected were spawned the previous winter within that direction (A. Nielsen and J. Padman, pers. the Hawkesbury system. A. flavimanus of 0+ comm.). Colonization of estuaries in northern. age were absent from Pittwater presumably be N.S.W. may be limited by water temperature be cause water that has ebbed from the Hawkesbury cause A. flavimanus spawns in winter. However, River proper does not flow into Pittwater when all that is known of the temperature tolerances of the tide floods, whereas it does enter Cowan reproduction in this species is that eggs can be Creek (A. Nielsen, pers. comm.). Thus there is incubated at temperatures as great as 13•Ž (Dotu little scope for larvae from the Hawkesbury River and Mito, 1955). to reach Pittwater. There is no evidence that A. flavimanus will The occurrence of 0+ oriental gobies in the dominate local estuarine and brackish-freshwater Hawkesbury system is significant because it shows fish assemblages, as reported for San Francisco that A. flavimanus can spread from a point source Bay (see references in Middleton, 1982). Popula of introduction (ports) to adjacent estuaries. We tion densities of estuarine gobies in N.S.W. - can do not know how the gobies first arrived in the be highly variable, due to the vagaries of larval Hawkesbury system. It seems reasonable to life (Bell, 1986; D. Hoese, pers. comm.). It assume, however, that spawning fish in Sydney remains to be seen whether populations of A. Harbour now provide a greater source of larvae flavimanus will display such variability or whether to disperse to the Hawkesbury system than does their spawning habits, combined with local hy ballast water. But larval dispersal may not be drological conditions, will confer an advantage - the only means by which larvae reached the permitting them to reach, and maintain, great Hawkesbury system. For example, larval A. abundance in the Australian estuaries they col flavimanus may settle on the hulls of pleasure onize. craft in Sydney Harbour, occupy outlet pipes in the hull, and then be transported to the Hawkesbu ry system. A specimen of the other goby- intro-

―229― 魚類学雑誌 Japan. J. Ichthyol. 34 (2), 1987

flavimanus (Temminck et Schlegel). Japan J. Acknowledgments Ichthyol., 4: 153-161. A. Nielsen (N.S.W. Department of Public Gray, C.A. and J.D. Bell. 1986. Consequences of two common methods for sampling fish and decapods Works) and J. Padman (Marine Studies Centre associated with the seagrass Zostera capricorni. at Sydney University) provided information on Mar. Ecol. Prog. Ser., 28: 43-48. river and ocean currents, respectively. D. Hoese, Hoese, D.F. 1973. The introduction of the gobiid D. Pollard and R. Williams commented on the fishes Acanthogobius flavimanus and Tridentiger draft manuscript. The study of seagrass fishes trigonocephalus in Australia. Koolewong, 2: 3-5. that yielded most of the data presented here was Masuda, H.,K. Amaoka, C. Araga, T. Uyeno and T. funded by Australian Marine Science and Tech Yoshino, eds. 1984. The fishes of the Japanese nologies Grant no. 83/1350. Archipelago. English text and plates. Tokai Univ. Press, Tokyo, xxii+437 pp., 370 pls. Literature cited Middleton, M.J. 1982. The oriental goby, Acantho gobius flavimanus (Temminck and Schlegel), an Baker, J.C. 1975. A contribution to the life history of introduced fish in the coastal waters of New South the yellowfin goby (Acanthogobiusflavimanus) in the Wales, Australia. J. Fish Biol., 21: 513-523. San Francisco Bay-delta area. M. Sc. Thesis, Paxton, J.R. and D.F. Hoese. 1985. The Japanese California State Univ., Sacramento. sea bass, Lateolabrax japonicus (Pisces, Percich Bell, J.D. 1986. The distributions of fish and thyidae), an apparent marine introduction into decapods in seagrass beds. Ph. D. Thesis, eastern Australia. Japan. J. Ichthyol., 31: 369-372. Macquarie Univ., Sydney. Bell, J.D., A.S. Steffe and M. Westoby. 1985. (JDB and RBT: Fisheries Research Institute, Depart Artificial seagrass: how useful is it for field experi ment of Agriculture, P.O. Box 21, Cronulla, N.S.W.- ments on fish and macroinvertebrates? J. Exp.- Mar. 2230, Australia; ASS: School of Biological Sciences, Biol. Ecol., 90: 171-177. Macquarie University, North Ryde, N.S.W. 2109, Brittan, M.R., A.B. Albrecht and J.D. Hopkirk. Australia) 1963. An oriental goby collected in the San Joaquin River Delta near Stockton, California. Calif. Fish Game, 40: 302-304. オ ー ス トラ リア に お け る マ ハ ゼ の 新 産 地 Brittan, M.R., J.D. Hopkirk, J.D. Connors and M. Johann D. Bell・Aldo S. Steffe・R. Bill Talbot Martin. 1970. Explosive spread of the oriental オ ー ス ト ラ リ ア,ニ ュ ー サ ウ ス ウ ェ ー ル ズ 州 の goby Acanthogobiusflavimanus in the San Francisco Hawkesbury河 川 水 系 が 同 国 に お け る マ ハ ゼ の 第3番 目 Bay-delta region of California. Proc. Calif. Acad. の 産 地 で あ る こ と が 確 認 さ れ た.採 集 標 本 は1984年12 Sci., IV, 38: 207-214. 月 の72個 体(全 長38-73mm)と1985年5月 の16 Bureau of Meteorology. 1979. Climatic survey, 個 体(全 長118-200mm)で あ る.こ れ ら の 大 き さ,出 Sydney Region 5, New South Wales. Australian 現 時 期 お よ び こ の 水 系 が 港 湾 で な い こ と か ら,既 に 他 Government Publishing Service, Canberra. 所 か ら の 侵 入 定 着 が あ り,水 系 内 に 補 給 源 が あ る 可 能 Dotu, Y. and S. Mito. 1955. On the breeding habits, 性 が 示 唆 さ れ た. larvae and young of the goby, Acanthogobius

―230―