Citation: Citation : Sidorovich, V. (2005) Impact of fishing with fyke-nets on the otter Lutra lutra population in Belarus and neighbouring regions of Russia IOSF Report [Available from http://www.otter.org/sidorovich_2005.html]
Impact of fishing with fyke-nets on the otter Lutra lutra population in Belarus and neighbouring regions of Russia
Vadim Sidorovich
Vertebrate Predation Research Group, Institute of Zoology, National Academy of Sciences of Belarus
Scientific Report of the Institute of Zoology, National Academy of Sciences of Belarus prepared by Dr Vadim Sidorovich, leader of the Vertebrate Predation Research Group to the project sponsor, International Otter Survival Foundation (IOSF), Isle of Skye, Scotland, UK
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| August 2005, Minsk |
THE PROJECT TEAM
| Dr.Vadim Sidorovich: leader of the Vertebrate Predation Research Group |  |
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Anna Sidorovich, assistant |
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Grigorij Janyta. assistant |
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Dr.lrina Solovej, assistant |
The countries of eastern Europe (eastern regions of Russia, Belarus, Latvia, Lithuania, eastern Poland, and Estonia) fairly long-term been in the same economy regime and historically having similar environments seemingly provide very similar habitat conditions for otters and human pressure on the species. Well preserved habitats (rivers and lakes), dense habitat network, and fairly high habitat carrying capacity supported the relatively dense otter populations, there (Ozolin & Rantin, 1992; Sidorovich, 1992, 1997; Ozolin & Pilat, 1995; Brzeziński & Romanowski, 1996; Rozhnov & Tumanov, 1996; Ulevičius & Balčiauskas, 1996; Sidorovich, 1997). On the other hand, first and foremost trapping markedly reduced the otter number even in good habitat conditions, what was quite common a decade ago (Ozolin & Rantins, 1992; Sidorovich, 1992, 1997; Rozhnov & Tumanov, 1996). Currently, perhaps the other threats act in the Otter populations in eastern Europe.
In 1990s, in contrast to the western Europe, where the otter populations globally declined, in the countries of eastern Europe had seems to be healthy populations of the endangered species. That has been reported in many papers published (Kiili, 1991, Ozolin & Rantins, 1992; Sidorovich, 1992, 1997; Ozolin & Pilat, 1995; Brzeziński & Romanowski, 1996; Rozhnov & Tumanov, 1996; Ulevičius & Balčiauskas, 1996; Sidorovich etal., 1997).
In 1990s in Belarus in the areas with protected fauna (different kinds of numerous reserves), the otter density varied up to 8, and on average it constituted 1.7-4.4 individuals per 10 km of river stretch depending on a habitat quality connected with a river dimensions (depth and width), flowing rate, density of floodplain waterbodies in old riverbeds, and beaver construction activity, first of all, damming (Sidorovich, 1992, 1997). In 1997-2001 in the adjacent regions (Pskov, Tver, Smolensk) of Russia, in the areas characterized by seems to be a low hunting pressure on otters the species density was also very high - up to 9, on average 4.1±2.2 (SD) otters per 10 km of river stretch (n=13). According to the data published by Pozhnov and Tumanov (1996), in 1990 about 28.9 Otters inhabited 100 km2 of forested area and about 16.9 otters were recorded per 100 km2 a total in the north-western region of the European part of Russia, and, respectively, about 18.6(8,9) in its central region. In eastern Poland (the Biatowieza reserve), we found from 1.1 to 5.0, on average 2.5 otters per 10 km of river stretch {Sidorovich et al 1996). In Lithuania, Ulevičius & Balčiauskas, (1996) censused from 1.8 to 5.7, mean 2.9-3.7 otters per 10 km of river stretch. In Latvia, on average 1.5-3.1 otters were registered per 10 km of watercourses (Ozolin & Rantins, 1992). So, the above listed data suggest that in Belarus and regions around the country the potential (respecting to the habitat carrying capacity) density of otters mostly comprises 2-5 individuals per 10 km of river stretch.
In 1990s, otters drowning in fykes and another fish-net types were also recorded. However, there was a quite strong control against fish-net usage provided by organisations responsible for the nature protection, and in spite of a special study on this well-known threat was not done, I assume, that such otter's deaths were not common in Belarus.
In those years as well as several decades before, the other marked threat for the otter populations in eastern Europe was drainage reclamation of wetlands and canalising of rivers. It had been a large-scale and pronounced deterioration of otter habitats, and carrying capacity of the canalised rivers with drained floodplains dropped down a lot (Sidorovich, 1992, 1997). Since late 1990s, drainage reclamation of swamps and river valleys mostly stopped in Belarus, because the shortage of financial support for this economy appeared. The created canals were gradually inhabited by beavers, and with their damming and digging of numerous burrows the habitat conditions for otters in the drained river valleys were improved. So, the negative factor of draining became not so dramatic. Since the late 1990s, otter trapping and furbearing on the whole have also declined, at least, in Belarus and Baltic countries due to loosing interest by people to wear fur clothes. Moreover, trapping appeared to be more expensive, what turned the majority of trappers away this business. After the furbearing and draining of river valleys have been declined in Belarus, an increase in the otter population density, first of all, in the hunting areas might be expected.
Actually, the further decrease in the otter numbers was registered in hunting areas as well as any other areas still having fairly good otter habitats, but used by people a lot. In such areas, doing census of otters along 24 rivers and their fragments, up to 3.3, on average only about 1.1±1.0 otters/10 km were registered. This is nearly twice less that it was before. As to six model rivers regularly (almost each winter) inspected, there the otter density decreased 1.9-33 (mean 2.4) fold to the winter 2002-2003 compared to that during the winter 1997-1998 (Figure 1A). At the same time, there was no any evident trend in the otter number at the model rivers draining reserves (Figure IB). There, otters were at the same level of a fairly high population density.
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| A: Hunting area used by people a lot, but still having fairly good riverine habitats |
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| B. Well preserved rivers in reserves with protected fauna |
| Figure 1: The changes in the otter population density (inds / 10 km stretch) at the model rivers located in reserves and areas commonly used by people. Belarus, the winter 2002-03 compared to the winter 1993-94 |
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Otter foraging in River |
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Otter eating fish |
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According to the information randomly learnt in Belarus and from the papers published for the western Europe (Jefferies et al, 1984; Madsen, 1991; Reuther, 2002), we assumed that the plausible cause was a sharp increase of the frequency of otters death in fishing nets, first and foremost, ones having fykes.
To study that a special questionnaire to locals (see the supplement) and five special expeditions were undertaken in Belarus in the period from December 2002 until March 2005. During such an expedition we also talked a lot with locals, especially with local fishers and hunters, in order to get more knowledge about otter's drowning in fykes and how intensive people use equipments having fykes. We did many inspections of aquatic ecosystems, first of all, those ones where locals fish with fykes. We studied the distribution of otter's activity in such habitats and investigated how locals use fykes there.
We revealed that both foraging activity of otters, especially family groups of the predator, and local poaching on fish with fykes were placed very similar, perhaps, due to the simple reason, i.e. the fish distribution. We found very strong correlation between the locations and intensity of otter sprainting and our estimates of local poaching with fykes (rs=0.96, P<0.001). Amongst such habitats were as follows: lake shallow waters overgrown with macrophytes in the warm season, lake inlets and outlets in winter and by spring (especially from end January to mid June), old riverbeds of medium-sized and big rivers, especially in their connections with rivers.
Having investigated the impact, we became convinced that fyke usage was faulty for the next step of the otter population decline. Usage of nets with fykes and just fykes have evidently increased in Belarus during the last decade, and in effect, otters drowning in such fishing equipment appeared to be much more frequent. Actually, the following data were obtained. 179 of 204 respondents (87.7%), who stated, that they know the situation relating "otter-fykes" good enough, confirmed possible dramatic negative effect of fishing with a net equipment on an otter population. They answered that they using of fishing nets, especially fykes, increased approximately 5-40 fold, and as far as they informed during the last two years from 1 to 30 (mean 11.3} otters drowned in fishing nets (92% in fykes) in the localities, where they live. The locality is approximately 50-360 km2. It is approximately 1-9, on average 2-3 otters died in fishing nets per 100 km2 per year. By extrapolating the census data on an unit area, it resulted that from 5 to 38 (mean about 9) otters live per 100 km2. So, currently each third otter dies being drowned in a fyke and other fish net. Taking into account, that the answered responders had no complete information about all otter's deaths, we assume that the average number of otters drowned in fykes may be even higher - about 3-5 otters per 100 km2. So, it mortality about 50%, which is the gained data on the otter demography (Sidorovich, 1997), the plausible reproduction rate of the population is not higher than 30%. Thus, we think that, at least, in Belarus and adjacent regions of Russia the main current threat for the otter population is drowning in fykes and other fishing nets, which recently became to be used much more frequently.
By analysing the impact in its seasonality (Figure 2), we found that otters mostly drown in fykes in the second half of winter (February-March) and in the beginning of the warm season (April-June). The activity of fish poacher with fykes was very similar. First, they catch fish at glacial lakes in inlets and outlets in February ~ early March, when fish go there due to a low concentration of oxygen in lakes. Secondly, fykers catch fish a lot in spawning period (April-June). Looking at the habitat distribution of otter's drowning in fykes (Figure 3), it is notable that mainly otters died in fykes located in various rivers, especially in inlets and outlets at glacial lakes
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| Figure 2: Seasonality in otters drowning in fykes in Belarus 2000-2004 |
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Figure 3: Habitat Distribution of otters drowning
in fykes in Belarus 2000-2004
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Fykes of local fish poachers |
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When we have learnt that, being aimed to mitigate the heavy impact on the otter population, a special poster-booklet (see the supplement) has been published and wide-spread, to whom it may concern in Belarus and neighbouring regions of Russia. Totally 680 copies were posted and directly given to people. This poster-booklet explains what is the otter as a species, its habitats, tracks and it points out on the newly appeared heavy threat to the otter population in Belarus, i.e. frequent drowning of otters in fykes and, in turn, the population decline. Following to the well-known and effective experience in western Europe to protect otters from drowning in fykes (Jefferies et al., 1984; Madsen, 1991; Reuther. 2002), we recommended to use a grid in the fyke entrance. The poster-booklet has an attractive look to be more effective in its influence on locals, who fish with fykes. We assumed that it would also help.
Indeed, quite many (about forty) locals, who received the poster-booklet, answered asking some details. We got in touch with them again, explaining everything, what they need. Finally, seventeen locals, who faced otter drowning in fish nets with fykes before, have reported about effectively of the grid use and none of otters were killed by them in such a way anymore. Even from this information from the seventeen locals we found, that approximately 30-40 otters were saved by our efforts in 2004, and, perhaps, it will work in future on this land.
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REFERENCES
Brzeziński, M. &. Romanowski, J., 1996. Otter distribution in Poland. -Report of the Seminar on the Conservation of the European Otter (Lutra lutra). Leeuwarden, the Netherlands, 7-11 June 1994. Council of Europe Publishing, 1996. P.69-70.
Jefferies, D.J., Green, J. and R. Green, 1984. Commercial fish traps and crustacean traps: serious cause of Otter Lutra lutra (L.) mortality in Britain and Europe. The Vincent Wildlife Trust, London, 47 pp.
Kiili, J., 1991. Distribution and number of otters in Estonia.- Proceedings V. International Otter Colloquium, Hankensbüttel 1989; 45-50.
Madsen,A.B., 1991. Otters (Lutra lutra) mortalities in fish traps and experiences with using stop-grids in Denmark. Habitat 6, 237-241.
Ozolin, J. & M. Rantins, 1992. The distribution and habitat conditions of the otter (Lutra lutra) in Latvia.- Proceedings of the first Baltic Conference. Tartu, P. 186-190.
Ozolin, J. & V.Pilat, 1995. Distribution and status of small and medium-sized carnivores in Latvia. - Ann. Zool.Fennici 32:21 -29.
Reuther, C., 2002. Otters and fyke nets - some aspects which need further attention. - IUCN Otter Spec. Group. Bull. 19(1) 2002: 7-20.
Rozhnov, V. & I. Tumanov, 1996. The status of the river otter in Russia.- Report of the Seminar on the Conservation of the European Otter (Lutra lutra). Leeuwarden, the Netherlands, 7-11 June 1994. Council of Europe Publishing, 1996.P.91-94.
Sidorovich, V.E., 1992. Otter (Lutra lutra) population structure in Belarus. Bull. MOIP (Moskow), 97(6): 43-51.[In Russian]
Sidorovich. V.E., 1997. Mustelids in Belarus. Evolutionary ecology, demography and interspecific relationships. Minsk, Zolotoy uley.
Sidorovich, V.E., Jedrzejewska, B. & W. Jedrzejewski, 1996. Winter distribution and abundance of mustelids and beavers in the river valleys of Bialowieza Primeval Forest. Acta Theriologica, 41: 155-170.
Ulevičius, A. & L. Balčiauskas, 1996. Otter population dcnsity in Lithuania - Report of the Seminar on the Conservation of the European Otter (Lutra lutra). Leeuwarden, the Netherlands, 7-11 June 1994. Council of Europe Publishing, 1996. P.84-86.