Salinity and Spawning of Nurseryfish, Kurtus Gulliveri, in the Adelaide

Salinity and spawning of nurseryfish, Kurtus gulliveri, in the Adelaide River of northern Australia with notes on electrofishing and photos of a male carrying eggs Tim M. Berra & Dion Wedd

Environmental Biology of Fishes

ISSN 0378-1909 Volume 100 Number 8

Environ Biol Fish (2017) 100:959-967 DOI 10.1007/s10641-017-0620-3

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1 23 Author's personal copy

Environ Biol Fish (2017) 100:959–967 DOI 10.1007/s10641-017-0620-3

Salinity and spawning of nurseryfish, Kurtus gulliveri, in the Adelaide River of northern Australia with notes on electrofishing and photos of a male carrying eggs

Tim M. Berra & Dion Wedd

Received: 23 November 2016 /Accepted: 5 May 2017 /Published online: 27 May 2017 # Springer Science+Business Media Dordrecht 2017

Abstract Nurseryfish are unique among fishes in that the Keywords Larvae . Spawning season males carry the fertilized eggs on a supraoccipital hook on their head. In an attempt to learn where, when, and at what salinities spawning occurs, an ichthyoplankton net was Introduction towed at 14 stations in the Adelaide River from the mouth (38 ppt) to the most upstream sections of the river The nurseryfish, Kurtus gulliveri (de Castelnau 1878) (0.1 ppt). Larval nurseryfish (5–27.5 mm SL) were col- (Kurtidae: Perciformes) is the only fish species known lected, preserved and measured, and water chemistry to exhibit Bforehead brooding^ (Balon 1975), that is, the parameters were recorded with each sample. Larvae were males carry the fertilized eggs on a supraoccipital hook. It found in the mid-reaches of the river during July–October, occurs in large, turbid rivers of northern Australia and most commonly at salinities between 13.6–0.5 ppt. southern New Guinea (Berra 2003). A congeneric spe- Salinities increased as the dry season progressed. Larvae cies, K. indicus, is found in southern Asia, but is not were not taken at salinities higher than 19 ppt, nor did they known to carry eggs, however, its life history is very occur in the upper-most reaches of the river system during poorly known (Berra 2007). Field studies to elucidate this time of the dry season. What nurseryfish do and the life history of K. gulliveri were commenced on the where they occur during the massive influx of freshwater Adelaide River in the Northern Territory of Australia in runoff during the wet season (November–April) remains a 2001. Prior to this, the most recent papers on the biology mystery. Electrofishing for nurseryfish proved to be inef- of this species were Weber (1913) and de Beaufort (1914). fective in the Adelaide River due to its extraordinary Berra and Wedd (2001) showed that nurseryfish diet turbidity which made recovery of stunned fish difficult consists of insect, isopods, and small fishes. Berra and and fresh material of males carrying eggs remains elusive. Humphrey (2002) examined the histology of the male’s Two historic photographs showing males carrying eggs hook and showed that the supraoccipital crest is hollow are described. and included soft tissue. They speculated that swelling of the fleshy part of the hook helps clamp the egg mass in place. Early life history stages were illustrated by Berra T. M. Berra : D. Wedd Research Institute for the Environment and Livelihoods, Charles and Neira (2003). The taxonomy and distribution of Darwin University, Darwin, Northern Territory 0909, Australia Kurtus was reviewed by Berra (2003) and photographs of yolk sac fry and egg masses were presented. T. M. Berra (*) Carpenter et al. (2004) provided CT scans of the Department of Evolution, Ecology & Organismal Biology, The Ohio State University, 1760 University Drive, Mansfield, OH unusual ribs and swim bladder arrangement whereby 44906, USA lobes of the swim bladder are encased in the concavities e-mail: [email protected] of expanded ribs creating a Brib window^ visible on the Author's personal copy

960 Environ Biol Fish (2017) 100:959–967 side of the fish. Berra and Aday (2004)showedthat isgiveninMesseletal.(1979)andBerra(2003). most nurseryfish in the population are one or two years Fourteen stations in the river from the mouth to the old, but a few can reach four years of age. Berra et al. uppermost headwaters were established and latitude (2004) observed egg carrying by male nurseryfish in the and longitude recorded (Fig. 1). A 500 μmmesh field. Lake (1971) (expanded by Merrick and Schmida ichthyoplankton net with a 50 cm2 mouth and length 1984) reported S. H. Midgley’s observation that a male of 2 m was towed with the incoming tidal flow at a boat nurseryfish carrying eggs was taken from the Saxby speed of c. 2 km/h for 10 min at each station. Water River at Taldora, Queensland. This location is hundreds chemistry parameters were recorded with a Horiba U10 of kilometers upstream in fresh water. This was a sig- Multiprobe Water Quality Monitor, and Secchi disk nificant observation at the time because Kurtus was then readings were taken. considered a marine species. Since many years of gill netting failed to produce a Epizootic ulcertative mycosis was reported for the male carrying eggs due to the detachment of the egg first time in nurseryfish by Humphrey and Berra (2006). mass when the fish struck the net (Berra et al. 2004), Berra (2006) presented a commissioned Aboriginal electrofishing was attempted as an alternative method. painting of nurseryfish in a paper on art and ichthyology. An electrofishing boat utilizing direct current of 115 V, Nurseryfish karyotype of 2 N = 44 was determined by 3.5 amps @ 25% wave form, and 100 Htz was Ezaz et al. (2007). Berra et al. (2007)showedgonad employed in water of salinity 0.5 ppt or less. Stream histology and demonstrated that females are batch segments shown to have larvae present in a plankton spawners. Sommer et al. (2011), using microsatellite sample were shocked for about 20–45 min each. DNA paternity analysis, pointed out that males associ- Localities shocked include: Marrakai Ck near Station ated with egg masses in the gill net were consistent with 9, Beatrice Ck Sta. 10, Goat Island Sta. 11, Manton Ck, being the genetic father of the embryos, but that genetic 1st Rock Bar Sta 12, and between Sta 12–13 (Fig. 1). variability was too low at the suite of loci employed to Gill netting with 4″ and 5″ mesh in Marrakai Creek was say with certainty that a given male was the father of a carried out on 14 Oct. 2016 to verify the presence of specific egg mass. Kurtus gulliveri where electrofishing was attempted. Eisemberg and Berra (2016) provided photographic evidence that nurseryfish are of commercial importance in the Kikori Market of Papua New Guinea. He et al. Results (2016) demonstrated that the male’s hook forms by resorption and growth of parts of the supraoccipital bone Larvae and salinity and provided 3D CT images of the neurocranium. Crook et al. (2015), using strontium isotope analysis Table 1 shows the number of larval nurseryfish caught in of otoliths, demonstrated that nurseryfish are euryhaline each 10-min plankton tow at each station along with the and make movements across a freshwater-estuarine sa- standard length (SL) of the larvae, the salinity of the river linity gradient. Berra et al. (2016) found larval at each site, the date, latitude, longitude and stream width. nurseryfish in the Adelaide River from June through No larvae were found in marine waters (Stations 1–4). January, but none were present during February–May The highest salinity in which a single larval nurseryfish and therefore concluded that the spawning season is was recorded was 19 ppt. The largest number of larvae June–January. It is with this background information were collected from the mid-reaches of the river (Stations that the present study was undertaken in 2016 to deter- 7–11), and their size ranged from 5 to 27.5 mm SL mine where in the Adelaide River nurseryfish spawn (Fig. 2). Therefore, we consider the region of the andatwhatsalinity. Adelaide River between Station 7 and 11 as the spawning grounds during this time period and with these salinities (Fig. 3). Salinities between 13.6–0.5 ppt seem the pre- Methods ferred conditions for spawning activity. The largest number of larvae in a single collection occurred at 2.0 ppt in The Adelaide River is a large, extremely turbid, tidal Station10(Table1). The uppermost Stations (13–14) are river about 65 km east of Darwin, the capital city of the very narrow, shallow, and littered with woody debris Northern Territory. A detailed description of this system compared to the rest of the river. Author's personal copy

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Reflective of the marine conditions, downstream Stations 1–6 yielded hydrozoan jellyfish (Limnomedusa), unidentified scyphazoan jellyfish, and the ctenophore Beroe. Chaetognaths were common at Stations 1– 4. Acetes shrimp were common at most upstream stations. Salinity continued to increase at all stations above Station 4 throughout the dry season. Other water chemistry parameters are listed in Table 2. Water temperature increased with time. Dissolved oxygen was always ad- equate at all stations except the uppermost Station 14 where values reached a low of 1.98 mg/l. No larvae were collected there, and this station was choked with filamentous green algae. The Adelaide is one of the most turbid rivers in Australia due to the very large water movement during 8-m spring tides. It is not unusual for the Secchi disk to disappear at 7.0 cm (Table 2). The upstream stations tend to be somewhat less turbid. The pH in the mid-reaches varies slightly from 7.8–8.5.

Electrofishing

Electrofishing for nurseryfish was not successful. No specimens were collected in seven samples. Species stunned included Thryssa scratchleyi, Nematalosa erebi, Liza ordensis, Lates calcarifer, Ambassis macleayi, Toxotes chatareus and a 3.5 m Crocodylus porosus. Gill netting readily caught nurseryfish (10 females, 20 males 150–250 mm SL) in Marrakai Creek, one of the electrofishing localities, but egg masses were not observed. Electrofishing was not a useful technique for capturing nurseryfish including the specific target of a male carrying eggs. This failure is most likely due to the elevated water turbidity (Table 2). Stunned fish are simply not visible. Only large species that disturb the surface are noticeable. The smaller fishes that sink are unseen and cannot be dip netted.

Photographs of males with eggs

In past years we have caught many male nurseryfish carrying eggs in Marrakai Creek only to watch in horror Fig. 1 Map of the Adelaide River showing locations of larval fish as the egg masses were detached from the male’shook and water chemistry stations. This map was extensively modified from Messel et al. (1979) by the gill net (Berra et al. 2004). Figure 4 is a living nurseryfish (225 mm SL) in a gill net with the eggs still attached to the male’s hook. When lifted out of the Author's personal copy

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Table 1 Number and size of larval nurseryfish collected at each Station in the Adelaide River during 2016 along with date, salinity, stream width, latitude and longitude

Station Name Stream Latitude & Longitude Date Salinity No. Avg. mm SL Width (m) 2016 ppt Kurtus (range)

1 95.0 km below bridge 1625 12o13.40′S131o13.50′E11Aug38.10 _ (Mouth) 2 82.4 km below bridge 483 12o17.56′S131o17.58′E11Aug38.10 _ (BD^ Ck) 3 74.2 km below bridge 337 12o21.32′S131o16.82′E11Aug36.90 _ (BE^ Ck) 4 65.8 km below bridge 231 12o23.61′S131o19.34′E11Aug34.30 _ 5 42.0 km below bridge 183 12o28.11′S131o21.13′E 8 Aug 19.0 1 22.0 8Sept 21.2 0 _ 6 31.0 km below bridge 157 12o30.32′S131o22.52′E 8 Aug 12.6 1 16.6 8 Sept 15.6 2 22.8 (22.5–23.1) 7 Oct 18.9 0 7 20.7 km below bridge 159 12o33.29′S131o22.59′E 8 Aug 7.1 4 14.4 (12.3–16.9) (Barra Farm) 8 Sept 10.2 18 15.1 (11.0–21.3) 7 Oct 13.6 14 15.9 (10.4–23.5) 8 10.9 km below bridge 133 12o36.66′S131o22.71′E 8 Aug 3.4 18 11.3 (6.0–21.4) (Scott’s Ck) 8 Sept 5.7 19 14.6 (6.7–26.9) 7 Oct 8.9 481 14.4 (10.0–24.5) 9 Bridge/Boat Ramp 144 12o39.63′S131o20.25′E 29 July 0.8 61 9.5 (5.7–15.9) 8 Sept 2.6 53 8.2 (5.0–18.1) 7Oct 4.6 67 14.2(7.0–23.8) 10 16.0 km above bridge 100 12o44.97′S131o16.91′E 29 July 0.3 18 10.4 (6.9–14.0) (Beatrice Ck) 8 Sept 1.0 70 9.1 (5.0–21.4) 7Oct 2.0 1652 11.7 (7.0–17.0) 11 25.1 km above bridge 98 12o46.77′S131o14.45′E29July0.27 15.1(9.8–27.5) (Goat Island) 8 Sept 0.5 30 12.1 (8.0–20.3) 7 Oct 0.9 7 15.5 (11.2–20.2) 12 31.9 km above bridge 105 12o49.20′S131o13.12′E 31 Aug 0.2 1 17.1 (1st Rock Bar) 26 Sept 0.5 1 12.6 13 40.6 km above bridge 41 12o52.83′S131o12.07′E 31 Aug 0.1 0 _ (2nd Rock Bar) 26 Sept 0.2 0 _ 14 49.1 km above bridge 12 12o54.92′S131o15.29′E 31 Aug 0.1 0 _ (Margaret R) 26 Sept 0.1 0.1 _

1 Does not include 81.7 mm SL specimen caught in plankton net 2 Does not include 60.0 mm SL specimen caught in plankton net water, the eggs separated from the male. This photo was Since, after 15 years of trying on hundreds of field provided by Tokyo Sea Life Park (TSLP) and was taken trips during eight separate visits to Australia, we were on 7 November 2008 in the main channel of the unable to secure a living male nurseryfish carrying eggs, Adelaide River about 5–6 km below the Arnhem we offer Fig. 5 as the only known photograph of a male Highway Bridge (Fig. 1) by biologists from TSLP as carrying the egg mass that remained in place. It is they collected Kurtus for their exhibit. noteworthy that this specimen was collected with Author's personal copy

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to ‘rescue’ the fish collection there-i.e. to wrap it up and arrange its dispatch to Port Moresby (where it was to be added into the BKanudi^ fish collection, which is now held in a building adjacent to the Biology Department at the UPNG). But as I recall, all (emphasis hers) of the Fig. 2 This 16.0 mm SL larval nurseryfish, Kurtus gulliveri,was specimens wrapped up were small ones-none larger than collected on 26 September 2016 at Station 9 and photographed by perhaps 250 mm FL…and no Kurtus. –so if the Kurtus Michael Hammer shortly after death. Note teeth on jaws was preserved, then it and other large fish must have and brain development been put in drums—but no drums of fish were there in the biology unit of OTML when I visited, and no one rotenone, not nets. Weber (1913) presented a drawing of directed me to them-and I remember asking about large a male with eggs which was reproduced by Berra fish^ (Kailola, in litt.9/7/16). (2007). Weber’s drawing is very similar to Fig. 5.We Andrew Storey (9/12/16 in litt.) writes: BJust back have attempted to locate the specimen in this photo- from trip to PNG…The specimen [male with eggs] …is graph, but to no avail. Because of its importance we not in the collection at Tabubil—that ‘collection’ is non- present a detailed account of our search for this existent unfortunately. It may have gone to DPI…so I specimen. doubt it would still be there…The site we collected The photo in Fig. 5 was taken by Kent G. Hortle and Kurtus with eggs from several years ago, Oxbow 8, is is used with his permission. The c. 210 mm SL male fish up the Strickland river, and we don’tplantobeupthere was collected by rotenone sampling near Bosset Lagoon in near future.^ in the Middle Fly River of Papua New Guinea (PNG) in William White, referring to the UPNG fish collection 1984. The fish was preserved and given to Ok Tedi wrote: BUnfortunately the collection lost about Mining Ltd. (OTML), Hortle’s employer at the time, 80% of its specimens between when it was at who maintained a fish collection at Tabubil, PNG. Kunudi and when it was moved to UPNG^ OTML most likely transferred the specimen to the (White, in litt. 8/26/16). He visited the PNG col- PNG Department of Primary Industry’s Kanudi fish lection in 2016, looked for the specimen and recollection, but this is not certain (Hortle in litt.8/24/16). ported BTherearequiteafewmaleKurtus in the Patricia Kailola, who was involved with the Kanudi PNG collection but none of them have any eggs fish collection for many years, has no recollection of the present on the head…^ BNo Ok Tedi material as I specimen. She oversaw the removal of the Kanudi col- could see^ (White, in litt.9/13/16).So,sadly,we lection to the University of Papua New Guinea (UPNG) conclude that the trail is cold and has come to a in 2000. She further writes: BIn 2003 I went to Ok Tedi dead end.

Fig. 3 Adelaide River at Station 10 facing upstream. Beatrice Creek enters the main channel at the left (east). The river is 100 m wide at this point. Note turbidity of river and mangroves and mud flats becoming exposed as tide recedes. Photo by Tim M. Berra Author's personal copy

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Table 2 Water chemistry parameters at Stations in the Adelaide River on dates of larval fish collections

Station Date Water pH Conductivity Turbidity Dissolved Saturation Secchi 2016 Temp Oxygen % Disk oC µS/cm NTU mg/l cm

1 11 Aug 25.9 8.49 52,200 12.5 5.24 81.0 71.0 2 11 Aug 25.7 8.37 57,200 38.4 5.30 83.5 42.0 3 11 Aug 25.6 8.28 56,600 51.8 5.04 78.1 27.5 4 11 Aug 26.1 8.13 52,100 44.0 4.87 74.6 30.5 5 8 Aug 25.2 7.91 30,400 258.0 5.90 80.6 7.0 8 Sept 28.4 7.51 33,600 261.0 5.08 71.4 12.0 6 8 Aug 25.3 8.40 21,000 248.0 6.30 83.0 7.0 8 Sept 28.2 7.89 25,500 177.0 4.75 64.0 10.0 7 Oct 30.3 7.68 30,400 165.0 5.00 72.7 15.0 7 8 Aug 25.2 8.40 13,100 307.0 5.69 70.6 10.0 8 Sept 28.2 7.99 17,400 218.0 5.47 74.6 16.0 7 Oct 30.3 7.88 22,600 126.0 4.19 60.5 27.5 8 8 Aug 25.3 8.27 6150 357.0 5.98 75.2 7.0 8 Sept 28.5 8.11 10,200 207.0 4.90 65.1 14.0 7 Oct 30.3 7.90 15,300 129 4.75 66.7 19.5 9 29 July 25.5 8.11 1590 _ 7.23 88.0 _ 8 Sept 29.4 8.14 4890 278 5.23 68.4 11.0 7 Oct 30.7 7.90 8280 205 4.5 61.8 13.0 10 29 July 25.3 7.85 618 _ 7.05 87.0 _ 8 Sept 29.6 8.45 2060 173 7.91 103.0 13.0 7 Oct 31.0 7.93 3730 102 6.00 80.2 20.0 11 29 July 26.2 7.92 363 244 8.29 103.2 _ 8 Sept 29.4 8.34 983 181 5.80 78.6 16.0 7 Oct 31.0 7.87 1770 59.6 6.05 81.4 26.0 12 31 Aug 27.5 7.48 459 60.7 6.42 81.5 19.2 26 Sept 30.9 7.31 998 36.7 5.79 75.3 21.0 13 31 Aug 27.6 7.37 304 17.9 6.01 77.5 50.0 26 Sept 30.8 7.38 477 16.4 7.90 106.2 46.0 14 31 Aug 26.9 6.85 221 7.0 2.24 28.5 89.0 26 Sept 30.1 7.21 254 8.0 1.98 26.6 106.5 * 7 Sept 29.7 6.79 98 0.1 5.30 70.5 _

*Darwin tap water

Discussion well have been a stray washed down by outgoing tide from upstream. Other studies that include all months of Based on the presence of larvae in plankton samples the year over a 12-year period show that larvae are (Table 1), we conclude that nurseryfish spawn in the present from June through January in the main channel mid-reaches of the Adelaide River at salinities between of the Adelaide between Station 9 and Marrakai Creek 13.6 and 0.5 ppt during the months of July–October. We (Berra et al. 2016), reflecting a lengthy spawning sea- suspect that it is the salinity gradient that is driving son. If spawning is directly correlated with salinity, we spawning activity, not the specific location (mid-reaches speculate that it may occur in different reaches of the of river). The one larva present at Station 5 at 19 ppt may river during different times of the year. Author's personal copy

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the river runs entirely fresh, often pushing a plug of fresh water several kilometers out to sea. As the monsoon retreats north in the early months of the year (March– May), the salinity of the river gradually increases from the mouth upstream. By the end of the dry season (Oct- Nov) salinities at Station 11 and upstream can be around 2–3 ppt. The reverse is true when the monsoon returns, that is the salinity is diluted with ever increasing amounts of fresh water until the entire river is running fresh. This may Fig. 4 Living male Kurtus gulliveri caught in gill net carrying egg influence the presence and absence of larvae throughout mass attached to his hook. The fish was 225 mm SL and weighed 162 g. It was caught in the main stream of the Adelaide River 5– the river system at different times of the year. For example 6 km downstream from the Adelaide River Bridge between Sta- we did not find any larvae in salinities higher than 19 ppt tions 8–9 by biologists from Tokyo Sea Life Park (TSLP) while (Station 4) during this study; however as the wet season collecting specimens for exhibition. The posterior part of the egg progresses and the salinity is diluted by an influx of fresh mass appears to still be attached to the male’s hook and anterior part of the egg mass has floated up and backward. Normally the egg water, salinities lower than 19 ppt will be recorded further mass would sit above the eyes (Fig. 5). The egg mass detached downstream than Station 4. The Wilshire Creek system from the male as it was removed from the net, and the fish died four (noted on the map as creeks B, C and D) are substantial days later. It is preserved at the TSLP. The photograph was provid- systems draining a coastal floodplain that is inundated with ed by Masato Ikeda and used with the permission to the TSLP fresh water during the height of the wet season. It is possible that over the course of six months when the Top Our findings are consistent with the results reported End receives the majority of its rainfall that the salinities of by Crook et al. (2015) who stated that most nurseryfish this downstream area will be between 0.5–19 ppt and, if had strontium isotope ratios indicative of periods of we are correct in saying that salinity is a primary require- saline residence (salinity >4 ppt) during their early life ment for Kurtus spawning in the Adelaide River, then it is history which was followed by a distinct transition into possible that spawning could occur from the mouth up to brackish (0.5–4 ppt) or fresh water (<0.5 ppt) later in and above Station 11 depending on the salinity at the life. They also showed that some nurseryfish were specific location over the course of the year. hatched in waters between 0.5–4 ppt. Our results extend Very little is known of the breeding biology of fishes those of Crook et al. (2015), whose methods could not in Australia’s northern rivers (King et al. 2013). Pusey discriminate between salinities of 4–38 ppt. We are able et al. (2015) collected 81 taxa in the estuaries of the South to show a spawning window of 0.5–13.6 ppt. Alligator River, but, with the exception of barramundi, We need more information about the general salinity Lates calcarifer, a protandrous hermaphrodite that characteristics of the Adelaide River over a 12-month spawns in brackish water, one would be hard put to say period. The salinity of the river varies according to the where, when and at what salinity most of these species amount of rain captured and transported within the catch- spawn. Because barramundi is the most important game ment during the wet season. At the height of the wet season species in Australia, much effort has been spent on

Fig. 5 The only known photograph of Kurtus gulliveri carrying an in that will allow the eggs mass to remain attached to the male. The situ egg mass. The specimen was collected and photographed by Kent specimen was taken near Bosset Lagoon in the Middle Fly River of Hortle using rotenone, which may be the only collection technique Papua New Guinea in 1984. It is estimated to be c. 210 mm SL Author's personal copy

966 Environ Biol Fish (2017) 100:959–967 understanding its biology. The timing of its spawning is in Fig. 4 after Bill Boustead called our attention to it. We appre- related to the beginning and strength of the wet season ciate the willingness to help locate the photo of the male with eggs exhibited by Kent Hortle, Patricia Kailola, Andrew Sanger, and (Larson and Martin 1990). What we present in this paper Will White. The spatial expertise of Ian Leiper of CDU who is a small step forward in understanding the unusual constructed the map (Fig. 1) is greatly appreciated. Field work breeding biology of one of the world’s most unique fishes was carried out with Northern Territory Fisheries Permit in one of the world’s most complex habitats. No.2015-2016/S17/3381, and the specimens have been de- posited in the Museum and Art Galleries of the Northern The ecological conditions of northern Australian rivers Territory fish collection under receipt number: R2016/001. All are such that it is difficult to make hard and fast predictions procedures performed in the study were in accordance with the for such systems. The arrival of the wet season can be early ethical standards of Charles Darwin University under Ethics Com- or late, the dry season may be prolonged or end a month mittee Permit A16021. This work was partially funded by a small grant from OSU’s Emeritus Academy. early. Collections made on incoming tides may be different than those made on outgoing tides. Data gathered on neap tides may be quite different from those recorded on spring References tides. Pusey et al. (2015) expressed similar reservations when trying to explain environmental variability in north- Balon EK (1975) Reproductive guilds of fishes: a proposal and ern rivers. definitions. J Fish Res Board Can 32:821–864 Nearly all of the 1650 mm average rainfall in the Top Berra TM (2003) Nurseryfish, Kurtus gulliveri (Perciformes: End near Darwin occurs during November to April. Kurtidae) from northern Australia: redescription, distribution, egg mass, and comparison with K. indicus from Southeast Normally, very little rain falls in the dry season, May to Asia. Ichthyological Explor Freshwat 14:295–306 October. However, each year is different. The two years Berra TM (2006) Art, ichthyology, Charles Darwin and the northern prior to this 2016 study had very weak wet seasons with territory of Australia. The Beagle: Records of the Museums – relatively low rainfall. The wet season began in mid- and Art Galleries of the Northern Territory 22:91 97 Berra TM (2007) Freshwater fish distribution. University of September of 2016 and record rainfalls were recorded. Chicago Press, Chicago This makes it very difficult to extrapolate from one year Berra TM, Aday DD (2004) Otolith description and age-and- to another. Our data were collected from late July to mid- growth of Kurtus gulliveri from northern Australia. J Fish – October. This sheds no light about what is happening in the Biol 65:354 362 Berra TM, Gomelsky B, Thompson BA, Wedd D (2007) downstream reaches of the river, which show marine levels Reproductive anatomy, gonad development and spawning of salinity in the dry season. When the estuary areas seasonality of nurseryfish, Kurtus gulliveri (Perciformes: become inundated with monsoonal rains in the wet season, Kurtidae). Aust J Zool 55:211–217 what does that do to the salinity, and do nurseryfish then Berra TM, Humphrey JD (2002) Gross anatomy and histology of the hook and skin of forehead brooding male nurseryfish, move into these areas? Could they possibly spawn there Kurtus gulliveri, from northern Australia. Environ Biol Fish and then? These questions need to be answered by long- 65:263–270 term studies throughout the year and throughout the length Berra TM, Neira FJ (2003) Early life history of the nurseryfish, of the river. Our data are a start to this ambitious goal. Kurtus gullieri (Perciformes: Kurtidae), from northern Australia. Copeia 2003:384–390 Furthermore, hydrological manipulation of the river Berra TM, Wedd D (2001) Alimentary canal anatomy and diet of the by water diversion or damn building could alter the nurseryfish, Kurtus gulliveri (Perciformes: Kurtidae) from the salinity of the estuary, reduce the area suitable for larval northern territory of Australia. The Beagle: Records of the occupancy, and degrade the freshwater nature of the river. Museums and Art Galleries of the Northern Territory 17:21–25 Berra TM, Wedd D, Allsop Q (2004) Observation of egg carrying by male nurseryfish, Kurtus gulliveri (Perciformes: Acknowledgements This work would not have been possible Kurtidae), and natural history notes from northern without the physical and logistical support of the Fisheries Re- Australia. The Beagle, Records of the Museum and Art search Staff of the Northern Territory Department of Primary Galleries of the Northern Territory 20:187–193 Industry and Fisheries. We thank Thor Saunders and Mark Grubert Berra TM, Wedd D, He Y (2016) Larval nurseryfish, Kurtus for making this cooperation possible and Quentin Allsop, Nathan gulliveri (Perciformes: Kurtidae), in the Adelaide River of Crofts, Graham Schultz, Dave Wilson, Chris Errity, Sean the northern territory: their season, fellow travelers, and Fitzpatrick, Brandon Cardona, Jeremy Rioli, and Kurtly Harvey unusual rib anatomy. Aust J Zool 64:262–266 for their skill in the field. Charles Darwin University and the Carpenter KE, Berra TM, Humphries JM Jr (2004) Swim bladder Museum and Art Galleries of the Northern Territory also provided and posterior lateral line nerve of the Nurseryfish, Kurtus valuable support. Michael Hammer kindly photographed Fig. 2 gulliveri (Perciformes: Kurtidae). J Morphol 260:193–200 and commented on an early version of the manuscript as did Crook DA, Wedd D, Berra TM (2015) Analysis of otolith Alison King. Masato Ikeda graciously supplied the original photo 87Sr/86Sr to elucidate salinity histories of Nurseryfish Author's personal copy

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Kurtus gulliveri (Perciformes:Kurtidae) in a tropical lowland Lake JS (1971) Freshwater fishes & rivers of Australia. Nelson, river in northern Australia. Freshwat Sci 34:609–619 Melbourne de Beaufort LF (1914) Die Anatomie und syssstematische Larson HK, Martin KC (1990) Freshwater fishes of the northern Stellung des Genus Kurtus Bloch. Gegenbaurs Morphol territory. Northern territory museum of arts and sciences. Jahrb 48:391–410 Darwin, NT, Australia de Castelnau F (1878) Australian fishes. Proc Linnean Soc NSW Merrick JR, Schmida GE (1984) Australian freshwater fishes: 2:225–249 biology and management. JR Merrick, School of Biological Eisemberg CC, Berra TM (2016) Fish species sold in the Kikori Sciences, Macquarie University, North Ryde, NSW, market, Papua New Guinea, with special reference to the Australia Nurseryfish, Kurtus gulliveri (Perciformes: Kurtidae). Messel H, Gans C, Wells AG, Green WJ (1979) Survey of tidal Fishes of Sahul ANGFA (Australia New Guinea Fish river systems in the northern Territory of Australia and their Association) 30(1):942–949 crocodile populations, Monograph no. 3. The Adelaide, Daly, Ezaz T, Berra TM, Graves JAM (2007) Karyotype of the and Moyle rivers. Pergamon Press, Sydney, 58 pp Australian nurseryfish, Kurtus gulliveri (Kurtidae: Pusey BJ, Kennard MJ, Larson HK, Alsop Q, Hammer M, Buckle Perciformes). Chromosome Sci 9:85–88 DJ (2015) Estuarine fishes of the south Alligator River, Kakadu national park, northern Australia. Mar Freshw Res. He Y, Berra TM, Wedd D (2016) A microtomographic osteology doi:10.1071/MF15221 of the forehead hook of nurseryfish, Kurtus gulliveri – Sommer JA, Li C, Brozek J, Bessert ML, Ortí G, Berra TM (2011) (Perciformes: Kurtidae). Copeia 2016(4):897 906 Low genetic diversity in nurseryfish, Kurtus gulliveri Humphrey JD, Berra TM (2006) Epizootic ulcerative syn- (Perciformes: Kurtidae), and an appraisal of its breeding drome in nurseryfish, Kurtus gulliveri (Perciformes: system using microsatellite loci. The Beagle: Records of the Kurtidae), in the northern Territory. Aust Soc Vet Museums and Art Galleries of the Northern Territory 27: Pathol Rep No 71:12–13 179–188 King AJ, Humphries P, McCasker NG (2013) Reproduction Weber M (1913) Süsswasserfische aus Niederländisch süd-und and early life history. In: Humphries P, Walker K (eds) nord-Neu-Guinea. Résultats de L’Expédition Scientifique Ecology of Australian freshwater fishes. CSIRO Néerlandaise á la Nouvelle-Guinée en 1907 et 1909. Publishing, Collingswood, pp 159–193 Zoologie, Leiden 9: 513–613, pl. 12–14