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The status of Danube beluga sturgeon (Huso huso): Past, present and future

Av Carolyn M. Rosten, Dalia Onara, Kate Hawley and Radu Suciu

Carolyn M. Rosten1 is a researcher with the Norwegian Institute for Water Research (NIVA), Pirsenteret, Havnegate 9, 7462 Trondheim, Norway. Dalia Onara is a scientific researcher with the Danube Delta National Institute (DDNI), Sturgeon Research Group, 165 Babadag Street, RO-8800, Tulcea, Romania. Kate L. Hawley is a research assistant with NIVA. Radu Suciu is leader of the Sturgeon Research group at the DDNI and CITES Scientific Authority for Acipenseriformes of Romania.

Status for Donau beluga drett og utsettelse av stør er også trådt i stør (Huso huso): kraft for å bedre fiskebestanden i områ­ Fortid, nåtid og fremtid det. En av de største utfordringene ligger Støren i Donau er i stadig tilbakegang, og i forebyggingen av illegalt fiske, gitt den langsiktige forandringer i populasjons­ gode markedsverdien på stør, og forval­ størrelse og struktur av størarter er blitt tingsprogrammet utarbeider stadige nye observert. I dette manuskriptet er beluga strategier for å håndtere utfordringene. stør (Huso huso) brukt som en flaggskips­ Som et ledd av dette ble Danube Sturgeon art for en casestudie av stør i Donau. Den Task Force (DSTF) opprettet i 2012 for å rumenske regjeringen brukte i 2006 doku­ ta denne utfordringen i årene som mentasjonen fra disse kritiske forandrin­ kommer. gene til å tvinge igjennom midlertidige fiskestanse på størarter, samt imple­ Summary mentere regionale overvåkingsstrategier. Sturgeons of the Danube River are in Overvåkingsprogrammet for juvenil stør decline. Long term changes in both som ble implementer på grunnlag av population size and structure of sturgeon dette har samlet ny og vital data på antall species have been observed. Beluga stur­ fisk samt nedstrøms migrasjonsmønster geon (Huso huso) as the flagship species for juvenil stør i Donau. Suksessfull opp­ of the Danube are used in this manuscript as a case study species. In 2006 the Roma­ 1 Author to whom correspondence should be addressed. nian government used documentation of Tel: +47 22 18 51 00; Fax: +47 22 18 52 00; these critical changes to enforce a fishing E-mail: [email protected]. moratorium on sturgeon species and

Vann I 04 2012 523 Innsendte artikler implement a regional monitoring stra­ powerdams Iron Gate I & II at river tegy. The juvenile sturgeon monitoring kilometres 942 and 863 in 1970 and 1984 programme implemented as part of these respectively (Hensel & Holcik 1997). changes has collected vital new data on These barriers divide the lower and mid the numbers and downstream migration Danube halving the historic spawning of Danube sturgeon. Juvenile sturgeon migrations of sturgeons which were have also been successfully produced and documented extending as far upstream released as part of the supportive stock­ as Vienna (Bacalbasa- Dobrovici 1997). ing programme. The greatest challenge The lower Danube extends downstream lies in the prevention of illegal fishing, from the Cerna River at river kilometre given the extreme value of sturgeon. The (rkm) 955 (Hensel and Holcik, 1997), with management programme is constantly the Romanian stretch reaching from the evolving to deal with the challenges of Iron Gates II dam at rkm 859 to the Danube conserving Danube sturgeon and in 2012 delta when the river meets the Black Sea. the Danube Sturgeon Task Force (DSTF) Many neighbouring countries border was created to take this challenge forwards. along the banks of the Danube (Ukraine, Moldova, Bulgaria and Serbia in the Lower Introduction Danube), figure 1. All countries borde­ Six species of sturgeon once migrated ring the river downstream of Iron Gate along the Danube for spawning: The ana­ II participate in the sturgeon fishery. The dromous species beluga; Huso huso, Rus­ river is, at its widest point, 1 km wide sian sturgeon; Acipenser gueldenstaedtii, and reaches maximum depths of up to stellate sturgeon; A. stellatus, and the 60 m. At the entrance to the Danube delta European Atlantic sturgeon; A sturio and the river splits into three main branches the river resident ship sturgeon; A nudi- forming the delta, figure 1. It also splits ventris (Bacalbasa- Dobrovici 1997). and re-joins at several places along its Only the beluga, Russian, stellate and length. sterlet; A. ruthenus remain and as with During the 20th Century, world demand sturgeon populations throughout the for sturgeon meat and caviar has inflated world, all species are in sharp decline. the economic value of sturgeon fishing, The Danube river system has long with the value of beluga caviar estimated been subjected to anthropogenic influ­ at $1000 per 100 grams (Suciu, 2005). ence from a number of sources altering This, when coupled with the develop­ the entire ecosystem. The fish commu­ ment of intense fishing pressure follo­ nity, in particular sturgeon species, has wing a lack of fishing controls after the been greatly impacted by these changes. Romanian revolution in 1989 (Kynard et Loss of habitat has occurred throughout al 2002), has caused the sharp decline in the system and in particular, historical recent documented catches of sturgeon. spawning grounds are no longer acces­ In 2006 all sturgeon fishing was sible due to the construction of the hydro­ banned for ten years by the Romanian

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Figure 1. Map of the Danube course through Romania giving the position of the two Iron Gate dams. government, with the exception of a few ery renowned throughout the world. His­ individuals to be used for a supportive torical catches of sturgeon are closely stocking programme and afterward related to the development of human returned live to the Danube. These settlements and fishing techniques on the strong measures were made possible Danube. Sturgeon have been harvested after documentation of changes in both on a commercial scale since the 4th and 5th the size and structure of the sturgeon Centuries and from the Middle Ages populations in recent years. This sophi­sticated gear was constructed taking manuscript takes beluga sturgeon, the advantage of the anadromous movements flagship species of the Danube Commis­ of these fish. One such method was the sion in Vienna, as a case study and dis­ construction of fishing weirs; fence traps cusses the changes in the population and made of wooden branches, spanning the the management approaches which were river and intersected with small gates for developed to aid the recovery of the species. river traffic to pass through, figure 2. These would be operated by a team of Past – Historical beluga 100-200 people, catching 1000-2000 stur­ population geons daily (Bacalbasa-Dobrovici 1997). The sturgeon stocks associated with the Such fishing methods resulted in a docu­ Danube have, over the centuries, formed mented decline of beluga as early as the the basis of a significant commercial fish­ 16th century and initiated international

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Figure 2. Historical method of sturgeon capture on the Danube consisting of fence traps spanning the entire river. These were very efficient capture methods and caught 1000-2000 sturgeon daily at times. Picture taken from Kunike (1979). disputes between upstream and down­ period (1920-2006) that records from the stream nations, culminating in the col­ Danube have been available, figure 3. A lapse of migratory sturgeon fishing in large crash occurred in the early 1940s, Austria during the 18th Century (Hensel coinciding with the Second World War & Holcik, 1997). and a reduction in fishing and therefore Limited sources of historical data fisheries records at that time. Stocks have exist for Danube sturgeon populations. also been in slow decline since the build­ However Antipa (1909) made meticulous ing of Iron Gate dams I and II. records of mean weight and sex ratio In addition to population size, popu­ data. These were compared to data lation structuring of beluga in the Danube record­ed as part of new, more detailed has altered during recent history. In the Romanian fishery catch statistics collec­ early 20th century (1903-1904) the sex ratio ted since 2003. Only catch statistics from of beluga was strongly skewed towards 2003 to 2005 are available because the males during summer and autumn sturgeon fishing ban was implemented months, gradually increasing towards a by the Romanian government in 2006. 50:50 balance during winter and spring, The beluga sturgeon stock has been suggesting earlier arrival of males prior relatively variable during the whole to spawning, figure 4. Fishery statistic

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Figure 3. Annual commercial catch of beluga sturgeon (Huso huso) in the lower Danube river / Romania. data from 2003 to 2005 suggest the same T = 3.18, p < 0.01). Interrogation of pattern of a bias towards males, evening length frequency of returning adult out as the spawning period approached. beluga and comparison with length at However, males were apparently 10 – 20 age taken from Ambroz (1960) demon­ % more abundant throughout the year strates an apparent lack of first time than 100 years previously, despite greater spawners in the population (first-time variation in the data due to lower sample spawning traditionally occurred at age size. These statistics were used to bring 13-15 years in females and younger in about the 10 year sturgeon moratorium, males (Otel 2007), particularly affecting though later communications with fis­ females (Figure 6). Lengths of returning hermen suggested that these records beluga during 2003-2005 suggested few might be biased, since it was still possible first returns of females below age 13, and to sell caviar on the internal black males below 12 or that the length at age market which indicates that the females of returning adults had increased. (particularly large specimens) were under reported in the fishery statistics. Present – Current Comparison of current and historical management data indicate a significant decrease in A regional monitoring system (RMS) of mean weight of both male and female sturgeon in the Danube was developed by beluga between the beginning of the 20th the Black Sea Sturgeon Management and 21st centuries, figure 5 (t-test; Female Action Group. This was agreed in April df = 18, T = 4.11, p < 0.005; Male df = 14, 2002 and put into practice in 2003 (Anon.

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Figure 4. Sex ratio of beluga sturgeon (Huso huso) in the Danube river (a) between 1903 and 1904 and (b) between 2003 and 2005.

2003). The RMS records both adult catch from 2001 until the sturgeon fishery ban data and also supported a juvenile moni­ in 2006. Juvenile monitoring is conduct­ed toring programme (first undertaken in annually during the downstream migra­ 2000). tion phase of young of the year (YOY). For the adult monitoring component Juveniles are caught with trammel nets of the RMS, variables including catch to provide catch per unit effort (CPUE) location and date, species, sex, standard statistics and prior to release all indivi­ length, total weight and gonad weight duals are weighed, measured and tagged were reported to the fishery authorities with Floyd fingerling tags to enable iden­ for every legally landed adult sturgeon tification upon subsequent capture.

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Figure 5. Mean weight of female and male beluga sturgeon in the Danube River in 1903-1904 (grey bar) and 2003-2005 (black bar). Weights differ significantly between time periods (t-test; Female df = 18, T = 4.11, p < 0.005; Male df = 14, T = 3.18, p < 0.01).

The new adult population size and management strategy. The goals of this structure data collected as part of the strategy were to prevent total extinction, RMS since 2003 led to the development to preserve the genetic diversity of popu­ of a more detailed Danube sturgeon lations / stocks, to rebuild a natural age

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Figure 6. Length frequency distribution (standard length) of migrating beluga sturgeon (Huso huso) in the Danube river during 2003-2005. Dotted bluelines mark length at age taken from Ambroz (1960) and modified to standard length using equations provided in Froese and Pauly (2009). class structure (in part by implementing Romanian waters of the Danube halted a supportive stocking programme), to (the Romanian sturgeon fishery was con­ restore natural recruitment and to sidered the largest of all Lower Danube develop sturgeon aquaculture to lower border countries (R. Suciu, Pers. Comm.). market pressure on wild populations. The single exception to the morato­ These objectives led to a joint ministerial rium is authorisation to capture a small order in May 2006 designed to support number of wild brood fish to be used for the conservation of wild sturgeon popu­ artificial propagation for both supportive lations and the development of sturgeon stocking of the Danube and development aquaculture in Romania. This in turn led of sturgeon aquaculture, in accordance to a ten year complete moratorium on with the objectives of the management the sturgeon fishery, which begun in strategy. A minimum effective number 2006. While the sturgeon fishery still of brood fish are used (based upon exists in other Danube bordering coun­ having a minimum effective number of tries, all legal fishing of sturgeon in 100 brood fish per generation interval

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(FAO/UNEP 1981), which in the case of Future beluga is 7 fish per year). Non-lethal arti­ Six years after the implementation of the ficial propagation procedures were sturgeon management plan (including implemented for the first time in Roma­ the fishing moratorium and the RMS) it nia and all brood fish are passive integra­ is appropriate to begin initial evaluations ted transponder (PIT) tagged and and modifications. The juvenile aspect, as entered onto a database of the National previously described, consists of three Agency for Fishery and Aquaculture of components; monitoring of downstream Romania (NAFA) prior to release back in migrations of wild juveniles, captive the Danube. All offspring are grown ­rearing of juveniles from wild brood- separately in families to a total length of stock for supportive stocking and captive ≥ 15 cm, tagged with coded wire tags rearing of juveniles from wild brood- (CWT) and released near to the catch stock for development of aquaculture. sites of the brood fish. This restocking The monitoring has provided vital new programme was interrupted in 2010 and data on the behaviour and environmental 2011 when changing politics in Romania requirements of YOY sturgeon in the prevented it from happening. However, Danube system. It will be continued as it it is expected to be reactivated by the develops into a long term monitoring release of juvenile sturgeons in autumn programme. Juvenile sturgeons have 2012. successfully been reared in hatcheries for Data on YOY migrations collected as both release into the wild at two to three part of the RMS has provided new months of age and for growing on for insights into juvenile beluga downstream aquaculture. 12 500, 15 000, 20 000 and migratory behaviour. Juveniles migrate 45 000 juvenile beluga were released in downstream in groups, seemingly acti­ 2006, 2007, 2008 and 2009 respectively as vely by the grouping of individuals. Data part of the supportive stocking pro­ on downstream migration of beluga gramme. 94% in 2007, 79% in 2008 and juveniles in the Volga River (Khodorev­ 69 % in 2009 (16 of 17, 15 of 19 and skaya et al 2009) do not refer to such a respectively 9 of 13 individuals caught) of migratory behaviour. Increased under­ brood fish were released alive back into standing of the juvenile migratory beha­ the Danube after use for artificial propa­ viour will assist in designing the most gation. First returns of hatchery release appropriate release strategy for hatchery sturgeon (stellate, as the species with the raised juvenile sturgeon as part of the shortest age at maturity) should occur in supportive stocking scheme. It will also 2012, beluga should follow in 2018. This help in implementing measures (such as will enable the first evaluation of this part protection of feeding areas in the down­ of the management programme. While stream areas of the Lower Danube) to supportive stocking cannot be seen as a maximise survival and arrival of juveni­ long term solution for conserving les at the Black Sea. Danube sturgeon species (Doukakis et al,

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2010) it is considered to provide an the fishery. A recent project, antonym important interim measure alongside Best Combat, funded by the Norwegian other conservation actions (DSTF 2012). Cooperation Programme for Economic The greatest challenge to the Danube Growth and Sustainable Development in sturgeon management plan stems from Romania and the Romanian Ministry of the closure of the sturgeon fishery. In the Environment, investigated these Romanian waters while all recorded, social dependences and needs and the legal fishing and sale of beluga and other potential for the creation of sturgeon sturgeon species has ceased, there are ecotourism on the Danube, as well as the indications that illegal fishing persists, current genetic and ecological status of perhaps even at a high level. The limiting beluga sturgeon in the lower Danube. factor in terms of success is in the imple­ This multifaceted approach was unique mentation of the moratorium. To prevent in its approach and increased communi­ such an economically enticing activity cation with sturgeon fishermen and on a river as big and complex as the improved motivation towards the mana­ Danube requires an enormous control­ gement measures put in place to restore ling presence on the river and accord­ the fishery. ingly immense funds to be able to do so. A combined approach is required not Romania is currently undergoing rapid only in a topical sense but also from an change in its status as a new EU member international perspective. In January state, but nevertheless such enforcement 2012 the Danube Sturgeon Task Force of the moratorium is not reasonable to (DSTF) was founded by a group of stur­ expect. Romania is also not alone in this geon experts, NGO delegates, and repre­ task. The lower Danube passes through sentatives of the International Com­ four countries before it reaches the Black mission for the Protection of Danube Sea and a coordinated action is required River (ICPDR), the Danube Strategy and for conservation measures to succeed. national governments in the frame of the A further means of improving the EU Strategy for the Danube Region, Pri­ success of the fishery management would ority Area 6 (Biodiversity) (http://www. be to address the importance of the stur­ dstf.eu). The DSTF aims to coordinate geon fishery from a social perspective. and foster the conservation of highly Sturgeon fishing is a historical legacy of endangered native sturgeon species in the Danube and many villages and towns the Danube River Basin and the Black have developed centred around the best Sea by promoting the implementation of sturgeon fishing locations. Addressing the Program “STURGEON 2020”. The the needs of these communities and main goal of this program is to secure assisting with the creation of new econo­ viable populations of wild sturgeon by mic focuses will enhance the likelihood reversing the current declining trends of success of the management of adult for all sturgeon species, increasing the sturgeon catches and thus recovery of protection status of their habitats and

532 Vann I 04 2012 Innsendte artikler restoring the migratory movements, by development of fish passage at migration year 2020. To achieve this, the DSTF blockages along the Danube, identifica­ coordinates intensive cooperation bet­ tion of key habitats and restoration needs ween the political, managerial and and development of stock assessment implementation levels at basin-wide systems. scale. The objectives and actions for the This trend of increased international DSTF strategy to implement the Stur­ collaboration with mutual goals for geon 2020 program are based on those of Danube sturgeon is hopefully the tur­ the Danube Sturgeon Action Plan (SAP) ning point for sturgeon conservation on which can be grouped into four major the Danube. After centuries of exploita­ categories: tion the time has now come for the rever­ 1. basin-wide coordination of sturgeon sal of damages and rebuilding towards a policy and best-practice management; brighter future for Danube sturgeon spe­ 2. legislation and enforcement controls cies. for sturgeon fisheries and trade; Financial support was provided by 3. conservation of sturgeon species and the Norwegian cooperation Programme populations, including their genetic for Economic Growth and Sustainable integrity; development in Bulgaria and Romania, 4. protection, management and resto­ administered by Innovation Norway ration of sturgeon habitats, including with co-financing from the Romanian reopening of migration routes. Ministry of Environment and Forests – European Union Funded Programme Due to the international nature of the Unit. The authors would like to thank Danube River and its sturgeon species it Marian Paraschiv, Dana Holostenco and is only by such a cross boarder approach Marian Iani for profitable discussion. such as the DSTF that a difference can be made to the Danube sturgeon conserva­ References tion status. Ambroz A. I. (1960) Beluga of the Black The DSTF will drive different rese­ Sea. Scientific Annals of the Kishinev Uni- arch priorities which, when combined versity, tom. LVI, Ichthyology: 77 – 84 (In with the policy and enforcement measu­ Russian). res, are hoped to turn around the fate of Danube sturgeon. In terms of research it Anonymous (2003) Regional Strategy for prioritises development of gene banks the Conservation and Sustainable Mana­ and a standardisation of breeding and gement of Sturgeon Populations of the rearing practice for an international sup­ N-W Black Sea and Lower Danube River portive stocking programme as a short in accordance with CITES. Agreed docu­ term conservation goal. This must be ment of the Second Regional CITES implemented alongside long term rese­ Meeting on Sturgeon Conservation, arch objectives including evaluation and Tulcea, 26 November 2003, 7 pp.

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Antipa, G. (1909) Ichtyological Fauna of Khodorevskaya R.P, Ruban G.I, Pavlov Romania. Inst. De Arte Grafice “Carol D.S. 2009. Behaviour, migrations, distri­ Göbl” Bucuresti 264-270 (in Romanian). bution, and stocks of sturgeons in the Volga – Caspian basin. Sturgeon Conser- Bacalbaşa-Dobrovici, N. (1997) Endan­ vation Society: Special Publication No 3, gered migratory sturgeons of the lower Neu Wulmsdorf, Germany: 89-112. Danube River and its delta. Environmen- tal Biology of Fishes 48:201-207. Kunike, Adolph (1979) Donau-Ansichten vom Ursprunge bis zum Ausflusse ins Doukakis, P., Babock, E. A., Pikitch, E. K., Meer. Wien 1824. 2.Teil : von Belgrad bis Sharov, A. R., Biamukhanov, M., Erbule­ zur Mündung ins Schwarze Meer nach kov, S., Bokova, Y. and Nimatov, A. 2010 der Natur aufgenommen von Ludwig Management and recovery options for Ermini. Abbildung Nr. 247: Der Hausen­ Ural River beluga sturgeon. Conservation fang beim Dorfe Tufesti (In German). Biology 24:769-777. Kynard, B., Suciu, R. and Horgan, M. (2002) Migration and habitats of diadro­ Danube Sturgeon Task Force (DSTF) mous Danube River sturgeons in Roma­ 2012 Roof strategy document. www.dstf.eu nia 1998-2000 Journal of Applied FAO / UNEP, 1981. Conservation of the Icthyology 18: 529-535. genetic resources of fish: problems and recommendations. Report of the Expert Otel, V. 2007. The atlas of the fish species Consultation on the genetic resources of of the Danube Delta Biosphere Reserve. fish. Rome, 9 – 13 June 1980. FAO Fish. Ed. Centrul de Informare Tehnologica Tech. Pap., 217: 43 pp. Delta Dunarii, Tulcea (In Romanian).

Froese, R., and Pauly, D. Editors. (2009). Suciu, R., Suciu, M. & Paraschiv, M. FishBase.World Wide Web electronic (2005): Contributions to spawning eco­ publication. www.fishbase.org, version logy of beluga sturgeons (Huso huso) in (10/2009). the lower Danube River, Romania. Exten- ded Abstracts of the International Sturgeon Hensel, K. and Holcik J. (1997) Past and Symposium 5, 309-311. current status of sturgeons in the upper and middle Danube River. Enironmental Biology of Fishes 48: 185-200.

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