Colored egg cockle, Azov-Black Sea cockle, Adacna colorata Eichwald, 1829, Glycymeris colorata Eichwald, 1829, Monodacna colorata (Eichwald, 1829), Monodacna colorata var. razelmiana Borcea, 1926, Monodacna colorata var. tanaisiana Milachewitch, 1916 Hypanis colorata (Eichwald, 1829)

Nonindigenous Occurrences: From 1951-1956, this species was intentionally stocked in the Veselovsky Reservoir (Kruglova 1961, Zhuravel 1969, Zhuravel 1975). It appeared in the Caspian in 1959 after the opening of the Volga-Don Canal (Saenkova 1956). In 1960, it was found in the lower Volga above Astrakhan City (Kosova 1963) and in August 1961, in the Volga Delta and near Baranovsky Island. It has since been introduced to Lake Balkhash (Kantor et al. 2010).

This species filter feeds on planktonic green algae, diatoms, and detritus, and is preyed upon by bottom-dwelling fish (Zaitsev and Ozturk 2001). Biomass of this species is highly variable based upon season, year, or its relative abundance among other species. In the Azov Sea, it is capable of reaching biomass densities of up to 600 g/m2 in favorable conditions. During harsh environmental circumstances, biomass density may become greatly reduced. This was observed in 2003 when severe winter conditions caused average densities in the Azov Sea to drop to 3.2 g/m2. When shallow water regions become chilled, sexually immature individuals die out, while 2-3 year old individuals migrate to deeper waters of 4-5 m (Shokhin et al. 2006).

Potential pathway of introduction: Trans-oceanic shipping (NOBOB vessels)

The introduction and spread of Monodacna colorata to non-native locations throughout Europe was facilitated by direct involvement from human vectors, likely including shipping (Grigorovich et al. 2002). Grigorovich et al. (2003) classify this species as a potential Great Lakes invader through ballast-mediated (NOBOB) introduction from ships originating in the Black-Azov Sea basin, though with reduced invasion likelihood due to ballast exchange or flushing. Specimens from the Caspian Sea are known to tolerate salinities up to 10 ppt (Karpevich 1960), while those from the Azov Sea quickly die in salinities greater than 5 ppt (Zenkevich 1963). These physiological restrictions are expected to reduce the probability of introduction under current ballast water regulations (30 ppt flushing).

Monodacna colorata has a moderate probability of establishment if introduced to the Great Lakes (Confidence level: Moderate).

Specimens from the Caspian Sea are known to tolerate salinities of 1-10 ppt (Karpevich 1960), while those from the Azov die in salinities greater than 5 ppt (Zenkevich 1963).

This is well within the range of the Great Lakes; however, Shokhin et al. (2006) reported that juveniles best develop at a salinity of 5 ppt. This is higher than the typical range within the Great Lakes and may be a physiological factor that restricts establishment. Establishment may be further restricted by the inability of juveniles to overwinter; when shallow water regions become chilled, sexually immature individuals die out. Older (2-3 year old) individuals have adapted behaviorally to avoid these conditions by migrating to deeper waters of 4-5 m (Shokhin et al. 2006), but populations are still negatively affected. In 2003, severe winter conditions caused average biomass densities of M. colorata in areas of the Azov Sea to drop to 3.2 g/m2, down from usual densities of up to 600 g/m2 (Shokhin et al. 2006).

Hypanis colorata requires a sandy bottom environment with high oxygen content (Shokhin et al. 2006) and is reported to co-occur with the invasive Dreissena polymorpha in substrate at depths of 20-50 m (Kosova 1963). This habitat type is readily abundant in the Great Lakes, with possibly the exception of Lake Erie’s periodic anoxic conditions (Summers 2001). It feeds upon planktonic green algae, diatoms, and detritus (Zaitsev and Ozturk 2001), none of which are limiting within the Great Lakes. Hypanis colorata is likely to benefit from the predicted effects of climate change, including reduced ice-cover duration and warmer temperatures. This is evidenced by the massive reduction in biomass density in areas of the Azov Sea following harsh winter conditions in 2003 (Shokhin et al. 2006). Increased salinization, as predicted in the Great Lakes (Rahel and Olden 2008) is also likely to benefit this species, as juveniles best develop in salinity of 5 ppt and adults survive and reproduce in 8-9 ppt (Shokhin et al. 2006). This effect may also benefit H. colorata in terms of reduced competition with native bivalves (more than 40 species) that may not tolerate salinity increases.

There are no reported occurrences of M. colorata outcompeting another species within its native or introduced ranges throughout Europe. This species shows relatively low biomass densities in comparison to other species within benthic communities of Taganrog Bay in the Azov Sea (Shokhin et al. 2006) after once being reported as the dominant species there (Karatayev et al. 1997, Vorobiev 1949, Nekrasova 1971). In recent years, it has experienced native population reductions in areas of the Black Sea and is under strict protection in Romania (Popa et al. 2011).

Monodacna colorata is preyed upon by bottom-dwelling fish (Zaitsev and Ozturk 2001); however, the extent to which this predation will prevent the establishment of populations in the Great Lakes is unknown. It was intentionally stocked into the Veselovsky Reservoir, Russia from 1951-1956 for the purpose of enhancing fish diet (Grigorovich et al. 2002, Kruglova 1961, Zhuravel 1969, Zhuravel 1975). From there, it spread relatively quickly to other canals and reservoirs and reached the Caspian Sea and Volga delta—probably as a result of shipping traffic with the opening of the Volga-Don Canal (Grigorovich et al. 2002). Within 7 years of the opening of the canal in 1952, this species had spread from the Black-Azov Sea basin into the Caspian Sea (Saenkova 1956). In 1960, one year after appearing in the Caspian, this species was observed in the lower Volga River (Kosova 1963). Panov et al. (2009) classify this species as having a high probability of dispersal as well as a high probability of establishment once introduced to a new inland waterway based on information from Son (2007).

Summary of species impacts derived from literature review. Click on an icon to find out more...

Environmental

There is little or no evidence to support that Monodacna colorata has the potential for significant socio-economic impacts if introduced to the Great Lakes.

Panov et al. (2009) classify M. colorata as a white-list species, as it is able to readily disperse and establish but not at high risk for causing significant socio-economic impacts.

There is little or no evidence to support that Monodacna colorata has the potential for significant beneficial effects if introduced to the Great Lakes.

The related Hypanis invalida was intentionally stocked into the Veselovsky Reservoir from 1951-1956 for the purpose of enhancing fish diet (Grigorovich et al. 2002, Kruglova 1961, Zhuravel 1969, Zhuravel 1975), though substantial increases in fishery production since its introduction have not been reported. This species is also listed as being edible to humans (Bourquin 2002).

*Ballast water regulations applicable to this species are currently in place to prevent the introduction of nonindigenous species to the Great Lakes via shipping. See Title 33: Code of Federal Regulations, Part 151, Subparts C and D (33 CFR 151 C) for the most recent federal ballast water regulations applying to the Great Lakes and Hudson River.

Note: Check federal, state/provincial, and local regulations for the most up-to-date information.

Control
Biological
There are no known biological control methods for this species.

Physical
There are no known physical control methods for this species

Chemical
There are no known chemical control methods for this species.

Note: Check state/provincial and local regulations for the most up-to-date information regarding permits for control methods. Follow all label instructions.