Pseudogobius olorum ( Sauvage, 1880 )

Larson, Helen K. & Hammer, Michael P., 2021, A revision of the gobiid fish genus Pseudogobius (Teleostei, Gobiidae, Tridentigerinae), with description of seven new species from Australia and South-east Asia, Zootaxa 4961 (1), pp. 1-85 : 56-59

Pseudogobius olorum ( Sauvage, 1880)

Swan River goby

Figs 1 , 22–23 , Tables 1–5, 17

Gobius olorum Sauvage, 1880: 43 (Swan River, Western Australia).— Bauchot et al. 1991: 37 (Rivière des Cygnes).

Mugilogobius galwayi McCulloch and Waite, 1918: 50 , pl. 3, fig. 1 (Patawalunga Creek, near Adelaide, South Australia).— Koumans 1940: 172–173 (Patawalunga Ck., S. Australia); Glover 1976: 175 (Patawalonga Creek).

Ellogobius (Lizagobius) galwayi — Whitley 1933: 93 (south Australia).

Lizagobius olorum [in part]— Whitley 1964: 125 (Victoria), South and Western Australia, northward to the Hill River ; Tasmania ).

Pseudogobius olorum —[in part] Hoese & Larson 1980: 186–188 (from Moreton Bay to Geraldton); Allen 1989: 207, pl.50 (Murchison River, Western Australia); Humphries & Potter 1993: 193 (Wilson Inlet, south-western Australia); [in part] Gomon et al. 1994: 805 (Western Australia, South Australia); Larson 2001: 203 (Swan River; Coorong, South Australia); Hoese & Larson in Hoese et al. 2006: 1680 (Gulf St Vincent, SA to Horrocks, WA); [in part] Kuiter 1993: 358 (western Victoria to western Australia); Larson & Hoese 1996: 220 (western Victoria to Western Australia); Morgan et al. 1998: 37 (Kalbarri to Esperance); Hutchins 2001: 44 (Western Australia); [in part]; Allen et al. 2002: 282 (Murchison River, WA to about the South Australia-Victoria border); [in part] Hammer & Walker 2004: 89 (South Australia); Close & Gouws 2007: 288 (Torbay Inlet, Western Australia); Hoese & Larson in Gomon et al. 2008: 769 (Western Australia to western Victoria); Gomon et al. 2008: 769 (Western Australia, South Australia); [in part] Larson 2011: 237 (southern Australia); [in part] Hammer et al. 2012: 65 (South Australia); Hammer et al. 2021: 2 (south-western Australia, Murchison River to Adelaide [diagnosable at nuclear markers and with a distinct mtDNA lineage, with a hybrid zone in the east]).

Material Examined. WESTERN AUSTRALIA: Syntypes of Gobius olorum, MNHN A.1913 , 3(37.5–40), river in Australia, Castelnau . AMS I.19514-001, 5(38.5–47), Parry Inlet, W.A. Fisheries, 25 October 1976 ; AMS IA.7437, 2(21–29.5), Angove River , Two Peoples Bay , V. Serventy ; AMS I.33396-010, 1(41), Young Rocks, Wilson Inlet, F. Neira, January 1988 ; AMS I.17622-001, 50(29–46), Moana Caravan Park, St Vincent Gulf, D.F Hoese and party, 18 December 1973 ; NTM S.17889-001, 5(36–52), Swan River , H. Gill, 27 November 1984 ; NTM S.17885-001, 11(35–40), Swan River , H. Gill, 30 January 1985 ; S.17886-001, 8(20.5–42.5), landing at Wilson Inlet, H. Gill, 14 November 1987; NTM S.17887-001, 1(55), Soldiers Cove, Peel-Harvey Inlet, H. Gill, 16 September 1987 ; WAM P.25122-055, 4(33–37), Murchison Park, Galena, G . R. Allen, 25 November 1974 . SOUTH AUSTRALIA: Holotype of Mugilogobius galwayi, SAMA F. 583, 50.5 mm SL male, Patawalonga Creek , near Adelaide . AMS I.34800-001, 10(15–61), Walker Creek on Salt Creek / North Para Road, P. Unmack, 9 April 1994 ; AMS I.20159-003, 19(16.5– 30), Vivonne Bay , Kangaroo Island, D. Hoese and party, 2 March 1978 ; SAMA F.5006, 7(24.5–39), Minnimbbie Creek , near Lake Wangary, Eyre Peninsula, 21 March 1980 .

Additional material (no data taken). WESTERN AUSTRALIA: AMS I.15724-011, 11, Leschenault estuary, Bunbury, Collette and J. Paxton, 8 February 1970 ; NTM S.18298-001, 13, Canning River , Perth , MH 19-05 , M. Hammer and G. Moore, 10 April 2019 . SOUTH AUSTRALIA: SAMA F.6552, 13, Port Lincoln , W. Zeidler, 23 March 1980 ; AMS S,17627-002, 3, Port Wakefield , D.F. Hoese and W. Ivantsoff, 22 December 1973 .

Diagnosis. A large Pseudogobius with second dorsal rays I,8–9; anal rays I,7–9; pectoral rays 9–18; 15–17 segmented caudal rays, usually in 9/7 pattern; lateral scales 26–30; TRB 8–12; predorsal scales 8–11; opercle with several rows of small cycloid scales, cheek naked; shoulder girdle usually smooth, may be narrow bony to fleshy flange along edge; tongue blunt to rounded; lips thick and fleshy in large males; upper jaw teeth in outer row stout and conical, curved to fairly straight with slightly pointed to almost blunt tips; mid-side of body with dark brown elongate blotches or X-shaped spots, and small round blackish spot just before caudal fin base, vertically elongate dark brown mark along hypural crease (this mark may appear as two coalesced dark brown spots); found in freshwater to hypersaline lakes, estuaries of rivers, streams and mangroves, south-western Australia (Western Australia and South Australia) .

Description. Based on 60 specimens, 21–61 mm SL. An asterisk indicates the counts of the 38.5 mm SL MNHN male syntype of Gobius olorum ( Fig. 23D ).

First dorsal IV–VII, usually I,6*; second dorsal I,8–9 (usually 8*); anal I,7–9 (usually I,8*); pectoral rays 9–18 (usually 16*); segmented caudal rays 8/7–9/8, nearly always 9/7*; branched caudal rays 7/6 (in 3), 7/7 (2), 8/6* (7), 8/7 (33), 8/8 (1), 9/7 (8); unsegmented (procurrent) caudal rays 9/9 (in 1), 10/9 (1), 10/10 (1); lateral scale count 26–30 (usually 28, 29 in syntype); TRB 8–12 (usually 10, 9 in syntype); predorsal scale count 8–11 (usually 10*). Gill rakers on outer face of first arch 2+5 (in 4), 2+6 (7), 3+6 (4), 3+7 (5), 4+6 (1).

Body relatively slender, compressed. Head large and bluntly rounded, wider than deep, especially in males (HL 23.5–31.3% SL (mean 27.1%). Depth at posterior preopercular margin 55.0–70.0 HL (mean 61.0%). Width at posterior preopercular margin 57.0–84.0% HL (mean 70.2%). Mouth moderate, subterminal, horizontal to very slightly oblique; jaws reaching to vertical through mid-eye in adult males and to anterior part of eye in females; upper jaw 28.4–49.7% HL (mean 39.0%), jaws in male always larger than in female (mean 42.8% of HL versus 34% in females); lips thin, to fleshy and thick in large males, lower lip broadly fused to chin anteriorly; inner edge of lower lip with fine fimbriae. Eyes lateral, high on head, top forming part of dorsal profile, 18.8–30.0% HL (mean 24.5%). Snout rounded and slightly inflated, 24.3–34.2% HL (mean 28.4%). Interorbital moderate, 11.8–28.2% HL (mean 16.4%). Body depth at anal origin 16.5–22.8% SL (mean 19.3%). Caudal peduncle compressed, length 24.6–30.6% SL (mean 27.8%). Caudal peduncle depth 10.0–17.6% SL (mean 12.3%).

First dorsal fin roughly triangular with rounded margin, with first to fourth spines longest, usually third (in 21 of those measured) or first (in 17). Appressed first dorsal fin just reaching to second dorsal fin origin in adult males, fin falling short of second dorsal fin in females; fin length 15.1–23.2% SL (mean 19.1%). Third dorsal spine length 10.0–15.5% SL (mean 12.8%). Fourth dorsal spine length 10.7–14.1% SL (mean 13.1%). Second dorsal and anal fin heights moderate, fins rounded to pointed posteriorly with posteriormost rays longest, rays falling well short of caudal fin base when appressed. Pectoral fin oval to rounded, central rays longest, extending back to vertical just before anus, 19.7–24.4% SL (mean 21.5%). Pelvic fins rounded, not reaching anus, 17.8– 23.9% SL (mean 20.3%). Caudal fin narrow and slender, rounded posteriorly, 24.4–34.2% SL (mean 28.9%).

Anterior nostril in short tube, oriented down over upper lip. Posterior nostril rounded to oval, with very low rim, placed at mid-level of eye. Gill opening extending from pectoral fin base or to under mid-opercle. Gill rakers on outer face of first arch very short stubs. Shoulder girdle usually smooth, may have narrow bony to fleshy flange along edge. Tongue tip blunt to rounded; fleshy in larger males. Upper jaw teeth in 2–3 rows, teeth in outer row always largest and usually evenly spaced, stout and conical, curved to fairly straight with slightly pointed to almost blunt tips; teeth in inner rows very small, close-set and sharp. Lower jaw teeth in 3–5 rows, conical, and curved to almost upright in outermost row, with sharp tips; no symphyseal canines present. Teeth in females smaller than in males.

Body scales ctenoid to behind pectoral fin; cycloid scales on predorsal and pectoral fin base; opercle with several rows of small cycloid scales, lower quarter to half of opercle may be naked; belly usually with ctenoid scales anteriorly, cycloid on posterior half, or all scales cycloid. Lateral canals, pores and sensory papillae pattern as in Fig. 22 .

Coloration of preserved material. Head and body yellowish white to brownish, darker along dorsum and usually paler ventrally, scale margins usually darkened, noticeable even on dark specimens. Dorsum with about 8–9 short dark brown blotches, commencing on mid-nape; blotches may join diffuse oblique brown blotches on upper half of body. Mid-side of body with about six dark brown elongate blotches or X-shaped spots ending in small round blackish brown spot just before caudal fin base, and vertically elongate dark brown mark along hypural crease, mark may have small dark brown spot above and below it; hypural crease mark may appear as two coalesced dark brown spots. Predorsal with brown mottling and indistinct spots. Breast, pectoral fin base and belly plain brownish. Peritoneum blackish on dorsal half, ventral half silvery white. Snout and side of head dark brown, lips plain brown with chin always paler than lips. Dark brown marks may be present by lower rear edge of eye, just behind corner of mouth; indistinct dark brown bar from lower front edge of eye to upper lip may be present.

First dorsal fin transparent to slightly greyish with two dark brown bands along fin, one just above base and one at mid-fin, may be blackish spot in rear part of mid-fin band; fin margin with scattered brownish pigment which may form distinct marginal dark band. Second dorsal fin transparent to greyish with 5–6 irregular lines of elongate dark brown spots, becoming more diffuse posteriorly. Anal fin plain dark brown with translucent margin. Caudal fin transparent to greyish with 6–8 irregular dark brown lines, becoming diffuse and indiscernible ventrally and darker and more pronounced near dorsal edge close to fin base. Pectoral fin translucent, evenly scattered with fine melanophores. Pelvic fins and frenum greyish brown in males and whitish in females; in some males margin of fin distinctly whitish and contrasting with central dark region, occasionally dark area is split into two dark oblongs.

Coloration of fresh material. Based on photos of captive specimens ( Fig. 23 ). Head and body translucent brownish grey, paler ventrally, scale margins on upper half of body at least narrowly outlined with slightly darker pigment. About 7–9 diffuse brownish short saddles across dorsum; several of these with indistinct oblique narrow bars extending to mid-side of body, to join row of about eight dark brown paired spots extending from below first dorsal fin to middle of caudal peduncle. Dark brown spot at base of caudal fin just above midline and similar dark spot at lower base of fin; markings may be joined as irregular brown bar. Several dark brown blotches or spots present just above pectoral fin base. Peritoneum white, usually showing through body wall. Side of head with short dark brown bar from lower rear edge of eye across cheek, may be second short oblique dark mark from above upper jaw, or whole side of head dark and relatively unspotted. Lips whitish to pinkish white. Iris iridescent brownish grey to silvery pinkish grey with narrow pale ring around pupil.

First dorsal fin translucent yellowish to pale yellowish brown, always brighter yellow on proximal half of fin with two brown bands, one across centre and one near base, with bright blue spot at rear of fin at end of central brown band. Second dorsal fin translucent yellowish to pale yellowish brown with 2–3 indistinct brownish bands, dark pigment mostly present on rays, yellow broad fin margin. Anal fin brownish yellow with bright bluish white margin. Caudal fin transparent yellowish with about five irregular brownish bands. Pectoral fin transparent, with brown spot at base of uppermost few rays. Pelvic fins with translucent pale golden brownish rays.

Comparisons. This species is similar to the eastern Australian species P. eos but differs in having higher second dorsal and anal fin ray counts (I,8-9, usually I,8 second dorsal rays and I,7–9, usually I,8 anal rays versus second dorsal and anal rays I,6-8, usually I, 7 in P. eos ), higher TRB (usually 10 versus usually 8), more lateral scales (27–30 versus 25–27), more predorsal scales (usually 10 versus usually 7–8), and is more robust compared to the more elongate P. eos with a typically larger head in males (mean 27.8 versus 25.5% SL).

Distribution. Endemic to south-western Australia. Recorded from Murchison River in Western Australia to the Gulf St Vincent region of South Australia including Adelaide and Kangaroo Island. Hybrid individuals involving this species with P. eos occur in south-east South Australia (from just east of and including the Murray River estuary and lakes), south-west Victoria (Glenelg River area) and north-west Tasmania.

Ecology. Shallow-water estuarine to freshwater to hypersaline lakes; found in estuaries of rivers, streams and mangroves, at depths of 0– 3 m. Can extend some distance inland in freshwater situations, escpecially where secondary salinization has occurred following land clearing ( Morgan et al. 2003). Humphries & Potter (1993) described the diet of P. olorum in a sand and Ruppia seagrass habitat (detritus, amphipods, mollusc siphons, ostracods). Neira & Potter (1994) discuss the seasonal abundance of P. olorum larvae in a Western Australian estuary, where the species was the second most abundant after Engraulis australis . In the Swan River estuary, this species spawns in spring and autumn, with the young of that year spawning the following autumn when they are about five months old ( Morgan et al. 1998). Some survive to spawn again the following year, but the life span is usually one year ( Morgan et al. 1998).

Remarks. Eastern populations of this species were split as a second species, P. eos , supporting a previously purported divide at the Glenelg River in western Victoria ( Larson & Hoese 1996) and supported with molecular data ( Hammer et al. 2021). Genetic data indicates the central area of overlap (Murray Mouth to Glenelg River inclusive and north-west Tasmania) between the two taxa represents a hybrid zone. Putative hybrid specimens examined within this geographic zone from the Coorong (SAMA F.5123) were morphologically indistinguishable from P. olorum ; further work with tissue vouchered material would be beneficial to characterise hybrid individuals and to fully map the hybrid zone.

Figures

FIGURE 1A. Distribution maps of species in the genus Pseudogobius, based upon material examined and inspected (circles) with the type localities indicated (squares).

FIGURE 22. Sensory pores and papilla rows in Pseudogobius olorum, 39 mm SL male, NTM S.17886-001, Wilson Inlet, Western Australia. Drawing by HKL.

FIGURE 23. Pseudogobius olorum, south-western Australia, (A) captive male, Canning River, Perth; (B) captive female, Canning River, Perth; (C) fresh male (top) and female, NTM S.18298-001, Canning River, Perth; (D) preserved syntype of Gobius olorum, 38.5 mm SL male, MNHN A.1913, Swan River, Western Australia. Photos by MPH.