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 1 23 Your article is protected by copyright and all rights are held exclusively by Springer Science +Business Media Dordrecht. This e-offprint is for personal use only and shall not be self- archived in electronic repositories. If you wish to self-archive your article, please use the accepted manuscript version for posting on your own website. You may further deposit the accepted manuscript version in any repository, provided it is only made publicly available 12 months after official publication or later and provided acknowledgement is given to the original source of publication and a link is inserted to the published article on Springer's website. The link must be accompanied by the following text: "The final publication is available at link.springer.com”. 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 num- ber 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 Environ Biol Fish (2017) 100:959–967 961 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.