Saimaa ringed seal
|Saimaa ringed seal|
P. h. saimensis
|Pusa hispida saimensis|
The Norppa (Finnish: Saimaannorppa) is a subspecies of ringed seal (Pusa hispida). They are among the most endangered seals in the world, having a total population of only about 390 individuals. The only existing population of these seals is found in Lake Saimaa, Finland (hence the name). They have lived in complete isolation from other ringed seal species for around 9,500 years and have diverged into a morphologically and ecologically different subspecies of ringed seal. The population is descended from ringed seals that were separated from the rest when the land rose after the last ice age. This seal, along with the Ladoga seal and the Baikal seal, is one of the few living freshwater seals.
The habitat of the Saimaa ringed seal is Lake Saimaa, Finland. The lake spans a circumference of approximately 180 Km X 140 Km and It has an area of 443 sq mi (1,147 sq km) and is relatively shallow, averaging about 12m deep and has a max depth of 85 m. Lake Saimaa contains approximately 13,000 islands and has over 14,850 km of shoreline. The freshwater lake freezes over between the months of November and May. Leaving the seals to two types of habitats throughout the year; the ice habitat and open water habitat. The freezing accompanied with the lakes natural architecture create a labyrinth-like habitat for the seals. During summer months when the ice is melted these islands provide ample space for the seals to molt and breed.
Saimaa ringed seals are named as such due to their only habitat being Lake Saimaa, Finland. Thus meaning that their range is also only the waters and surrounding banks of Lake Saimaa.
An adult Saimaa ringed seal is between 85 and 160 centimetres (2.79 and 5.25 ft) in length and weighs between 50 and 90 kilograms (110 and 200 lb); males usually being larger than females. They are coloured dark gray, with a gray-black dorsal with circular white rings. The bottom is light gray. The Saimaa ringed seal is darker in color than other ringed seals.
The Saimaa ringed seal does not have an incredibly varied diet. They are generalist feeders and eat exclusively fish. The fish consumed consist primarily small schooling fish averaging 8.6 cm in length and up to 21 cm in length, while it has been shown that the pups eat slightly smaller fish than the average. The majority of their diet consists of vendace, smelt, perch and roach. The pups diet varies markedly from the adults in that their diet consists primarily of perch and roach found in the shallow water where they spend most of their time in their earlier months while the adults consume more vendace and smelt.
It was believed for a long time that the Saimaa ringed seal was competing with the commercial and recreational fishing industries and there were bounties paid on them until the 1940’s. However it has recently been proven that the Saimaa ringed seal has minimal to no effect on the fishing industry. They do not prey on the local endangered salmon species(Salmo salar m. Sebago, S. trutta m. lacustris, and Salvelinus alpines) and although they do prey on the valuable vendace population, the proportion of the vendace population to the amount consumed by the seals indicates that they do not compete with the local fishing industries.
Saimaa ringed seals have a gender ratio of 1:1 and become mature between the ages of 4 and 6. Their pregnancy rate is between 80 and 95 percent. Ringed seals' gestation lasts 11 months. Their pups are between 55 and 65 centimetres (1.80 and 2.13 ft), and 4 to 5 kilograms (8.8 to 11.0 lb) at birth. The Saimaa ringed seal's longevity is just over 20 years.
A study conducted from 1980-84 revealed that Saimaa ringed seals make burrowed dens close to the shore and they reproduce once a year due to their longevity.
Saimaa ringed seals have two kinds of lairs or dens; they have a haul out lair where no breeding takes place, and the breeding lair. Breeding lairs are located closer to the shore than haul out dens.
Diving is an important behavior for marine mammals as it is something they rely on for behaviors such as foraging and travelling. The duration of their dives increases from spring to autumn, which may be a result of food availability, but is interesting because they are one of the few land locked seal species. Many studies have been done to observe Saimaa ringed seal diving, and has been discovered to last longer than expected. Their average time for a long dive was recorded to last for 15 min and was believed to be an aerobic resting dive.
The average dive depth ranges from 10 to 15 m, however, their maximum dive depths were limited by environmental depth. The saimaa ringed seal has also been observed to have seasonal hauling-out patterns. In May and June, when the seals are molting, they are observed to haul out both day and night, however, in late summer they are only observed to haul out at night.
The saimaa ringed seal is able to complete their dives and navigate in their environment due to their highly developed vibrissae, also known as whiskers. Using their vibrissae they are able to detect sound and pressure waves in their otherwise dark environment.
The Saimaa ringed seal has been protected since 1955. In 1983, the population was between 100 and 150 seals. In 2005, it was about 270, but as a result of two unfavorable breeding seasons, 2006 and 2007, the number dropped down to 260. In 2013 the population was estimated at just over 300 and the population numbers were in a slight growth. The number of breeding-aged females was 87. It is thought that the immediate threat of extinction would be alleviated if the population grew to over 400 individuals. It is listed as endangered by the U.S. government under the Endangered Species Act.
In spring 2016, 79 pups were found, four of which were dead.
In order to protect the Saimaa ringed seal, there are voluntary fisheries restrictions in a part of their living areas. The most important form of restriction is a ban for fishing nets from April 15 to the end of June in about 15% of the lake; nearly all fishing is recreational. Bycatch mortality has, however, remained high with estimated mortality of 20–30 seals annually, most of them pups of the same year.
To reduce the by-catch mortality of seals aged over one year, it has been banned since 2011 to use certain fishing methods, such as strong mesh nets, large fish traps, and fish-baited hooks, in the main part of the Saimaa ringed seal’s habitat.
In 2016, one act and mutual agreements between authorities and owners of fishing waters replace earlier two acts. The fishing co-operatives get 1.7 euros per hectare to monitor that fishing limitations are followed. Net fishing (except of vendace nets) is forbidden between 15 April and end of June in certain areas, which have been drawn at 5 km radius from nesting sites.
Breeding success of Saimaa ringed seal depends on sufficient ice and snow cover. The loss of snow and ice caused by the ongoing climate change poses a direct threat to them. Human-made snowdrifts have proved to be successful in improving seals' breeding success during winters with poor snow conditions. Snowdrifts were tested for three winters, and from 2014 they have been used regularly.
Target of the protection is to have 400 ringed seals in Saimaa by year 2020.
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