Arch. Pol. Fish. (2013) 21: 169-177 DOI 10.2478/aopf-2013-0014 RESEARCH ARTICLE Spawning behaviour of Danube huchen from three Austrian rivers Manu Esteve, Günther Unfer, Kurt Pinter, Ignacio Doadrio Received – 20 September 2013/Accepted – 27 September 2013. Published online: 30 September 2013; ©Inland Fisheries Institute in Olsztyn, Poland Citation: Esteve M., Unfer G., Pinter K., Doadrio I. 2013 – Spawning behaviour of Danube huchen from three Austrian rivers – Arch. Pol. Fish. 21: 169-177. Abstract. A camera inside an underwater housing was used Introduction to record a pair of Danube huchen, Hucho hucho (L.) spawning at the Ybbs River, Austria. A description of spawning behaviour is made including observations of two The Danube huchen, Hucho hucho (L.) referred to other Danube huchen pairs recorded at the Rivers Mur and further as “huchen”, is a freshwater salmonid inhab- Pielach. Results were compared with the spawning behaviour iting the Danube River system in the European Black of Siberian taimen, Hucho taimen (Pall.), Manchurian trout, Sea watershed. It lives in well-oxygenated waters and Brachymystax lenok (Pall.) and Sakhalin taimen, Parahucho can grow to sizes ranging from 1500 to 1800 mm in perryi (Brevoort). Danube huchen females, likewise the Siberian taimen and Manchurian trout females, rest for length and 40 to 70 kg in weight (Holèik 1990, a variable number of minutes after the spawning act, before Kottelat and Freyhof 2007). As top predator, huchen covering the eggs with gentle tail beating. This behaviour joins is a key species that regulates the ecology of the Danube huchen with Siberian taimen intragenerically and montane and submontane water systems it inhabits Hucho with Brachymystax intergenerically, distinguishing it from Parahucho and strengthening our current conception of (Holèik et al. 1988). As the most-westerly distributed the Salmoninae subfamily. species of its genus, huchen is a key species in the evolutionary history of the Hucho group (Holèik Keywords: phylogeny of behaviour, underwater video, 1982). Finally, as a member of the genus Hucho, con- postspawning behaviour, male digging sidered to be basal in the Salmoninae subfamily (Crespi and Fulton 2004, Wilson and Williams 2010), it is an important link in the understanding of the evolution of all the salmonids. Unfortunately, its current status in Europe is critical as it has disap- + M. Esteve [ ], I. Doadrio peared from most of its original range, and only a few Departamento de Biodiversidad y Biología Evolutiva Museo Nacional de Ciencias Naturales (CSIC) self-sustaining populations survive. The loss of habi- Jose Gutierrez Abascal 2, Madrid, Spain tat space and quality from water regulation and pol- e-mail: [email protected] lution from industrial and agricultural development G. Unfer, K. Pinter is responsible for this dramatic decline (Holèik Department for Water, Atmosphere and Environment 1990). Today, most of the remaining populations are Institute of Hydrobiology and Aquatic Ecosystem Management University of Natural Resources and Life Sciences, Vienna, Austria thought to be largely dependent on stocking (Holèik 1995), with the consequent loss of genetic variability and other problems associated with hatchery fish 170 Manu Esteve et al. propagation (Fleming and Petersson 2001, Álvarez than English. However, this manuscript lacks details and Nicieza 2003, Araki et al. 2007, Fraser 2008). about the spawning act itself or the female behaviour Since huchen is an endemic species to the Dan- immediately after spawning. Witkowski (1988) pre- ube catchment area, Austria lies in the center of its sented a study of the spawning ecology of a huchen natural distribution range. Before human interfer- population in Poland. These observations, together ence, huchen inhabited the Austrian Danube and its with the works referred to by Holèik et al. (1988) and larger tributaries in the barbel and grayling zones to- later corroborated by Esteve et al. (2009a) with Sibe- talling over 2,500 km in length (Schmutz et al. 2002). rian taimen, identified a spawning behavioural sin- Stocks had already declined dramatically by the late gularity with respect to the other salmonines; namely nineteenth century (Jungwirth 1984) mainly due to that pair formation in huchen and Siberian taimen fragmented migration routes between the Danube occurs days or weeks before spawning starts (Esteve and tributaries as a result of hydropower develop- et al. 2009a). Interestingly, Holèik et al. (1988) re- ment and river channelization (Schmutz et al. 2002). ported another exceptional behaviour: huchen According to IUCN criteria (IUCN 2013) and the males, like females, contribute to digging the nests in Bern Convention (Appendix III), huchen is listed as which eggs are deposited. Reports of huchen as well an endangered species. In Austria today the largest as Siberian taimen male digging behaviour were later population of approximately 1,500 adult huchen in- reported by other authors, although none of these habits a 270-km segment of the Mur River; however, were based on their own observations (Mateyev et al. the Mur population has declined by 80% over the last 1998, Kottelat and Freyhof 2007, Freyhof and twenty years (Schmutz et al. 2011). Small, Kottelat 2008). This is a remarkable fact as male dig- self-sustaining populations are currently also found ging among the salmonids is only present in the in the Pielach, Drau, and Gail rivers. Huchen occurs Oncorhynchus genus, and it is thought to be the re- at very low densities in the approximately forty rivers sult of displacement reactions (McCart 1969, Esteve of its historic natural distribution in Austria 2007). (Schmutz et al. 2002). The Danube itself functions The validity of behaviour as a phylogenetic signal mainly as habitat for sub-adults and adults, while re- has been demonstrated repeatedly (Brooks and production and early development happen in the McLennan 2002 and references therein). tributaries. The River Ybbs is one of the most promis- Salmonines are categorized into three groups accord- ing areas for huchen restoration in the nearest future ing the female post-spawning behaviour from egg de- since habitat enhancement measures are being car- position to egg covering (Esteve et al. 2011): 1. ried out in it, and fish passes are being constructed to Brachymystax + Hucho: the female rests for a num- reopen migration barriers. In its lower reaches, ber of minutes and then digs to cover the eggs; 2. a small population of > 50 adult individuals has been Salvelinus: the female undulates her body over the established (Guttmann 2006, Unfer et al. 2012), and deposited eggs and then digs; 3. Salmo + Parahucho huchen occurs in small numbers up to the village of + Oncorhynchus: female digs to cover the eggs im- Göstling. mediately after spawning. This classification was Despite its status as one of the largest, only sur- made before there was any knowledge of female passed by the co-generic Siberian taimen, and most huchen post-spawning behaviour. In the present pa- emblematic members of the entire Salmoninae per, the validity of this behaviour as a phylogenetic subfamily, a complete description of the huchen tool is assumed to predict, firstly, that after having spawning ritual has not been compiled to date. spawned the female will rest for a number of minutes Holèik et al. (1988), in an impressive monograph before covering the eggs, and, secondly, that the male provide a consensus review of huchen spawning will not dig. These predictions were tested using an ecology and behaviour referencing the written work underwater video recording system that permitted of several authors who published in languages other monitoring huchen spawning in the wild without Spawning behaviour of Danube huchen from three Austrian rivers 171 disrupting natural behaviour. The aim of this study brown trout, Salmo trutta L., and rainbow trout, was to describe huchen spawning behaviour and to Oncorhynchus mykiss (Walbaum). compare these results with the spawning behaviours The River Mur is located in central Austria and is of other salmonids. 460 km long. Its source is in the eastern Alps, and its main runoff direction is south-east through Slovenia, Croatia, and Hungary before it discharges into the Material and methods River Drava, a tributary of the Danube. At the spawn- ing site (47°7’42.85"N; 14°14’40.83"E), the river is a sixth order stream with an average width of 35 m. Study area The dominant species in this section of the river is grayling, accompanied by brown trout and rainbow Underwater recordings were made during the 2011 trout. spring spawning season on the Pielach (April 1), Ybbs (April 8), and Mur (April 10) rivers in Austria (Fig. 1). The Pielach is a fourth order stream that Underwater video drains into the Danube. At 74 km long, its source is located in the foothills of the northern limestone A Sony HDR-HC7 color digital video camera pre-Alps. Huchen were recorded in the lower course mounted inside an underwater housing was used to of the river (48°12’33.26"N, 15°24’05.84"E) close to record the fish. The video signal from the camera was transmitted via cable to a digital recorder located on land. The camera was positioned approximately 0.75 m from the nest in which a female had been observed previously. Redds, which are disturbed areas of gravel containing nests, were located in tail pool ar- eas with decreased water depths ranging from 1 to 0.5 m and increased flow velocity. Males and females presented with very little sexual dimorphism (Fig. 2), and in each of the rivers where recordings were made the male was slightly darker and redder in compari- son to the female. Sex was confirmed by the behav- Figure 1. Map showing the three spawning sites in this study. iours exhibited. The fish were positioned one slightly behind the other; the male was identified as the fish the mouth of the Danube.