Oriental Weatherfish, Misgurnus Anguillicaudatus (Candor, 1824)
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Invasive Species Profile Oriental Weatherfish, Misgurnus anguillicaudatus (Candor, 1824) Ben Frable FISH 423 December 3rd, 2008 Diagnostic Information are imbedded and irregularly distributed along the body; Berg (1949) gave scale counts of 105- Common names: Oriental weatherfish, oriental 180 laterally. Another characteristic to weather loach, weather loach, dojo and dojo distinguish it from other species is that it has loach elongated peduncular keels with pre-current caudal rays creating conspicuous adipose crests Classification: on the dorsal and ventral sides of the caudal Kingdom: Animalia peduncle, see Fig. 1b (Berg 1949; Kottelat Phylum: Chordata 1998). The caudal peduncle is also fairly short Class: Actinopterygii and less than the length of the head (Nichols Order: Cypriniformes 1943). On many specimens there is a large Family: Cobitidae pigmented spot located dorsally above the base Genus: Misgurnus of the caudal fin (Berg 1949). Also, it has been Species: anguillicaudatus noted that the eyes of M. anguillicaudatus are visibly larger than those of the European Basic identification key weather loach Misgurnus fossilis (Berg 1949). This species is also somewhat sexually The identification of the oriental dimorphic with males having pectoral fins that weatherfish is fairly distinct; however, no are longer than their head. Also, the females modern meristic analysis or comparisons have tend to have a fuller abdomen than males that is been done on the genus. In general, the species mainly associated with the large size of their in long with an anguillid body shape having a ovaries (Yamamoto and Tagawa 2000). A less ventrally located mouth with ten rostral barbells, noticeable character of the males is that the 4 of which are receded. The dorsal fin placed ventral base of the second pectoral ray broadens two-thirds the length of the body posteriorally into a rounded plate and covers the bases of the and the pectoral fins are readily placed ventrally other pectoral rays (Berg 1949). behind the opercular opening. The body color is In Oregon, Logan et al. (1996) collected one yellow-brown to brown with irregularly specimen of the Chinese fine-scaled loach distributed areas of pigmentation without Misgurnus mizolepis, another non-native species distinct lateral banding (Berg 1949). Nichols that is closely related to M. anguillicaudatus. (1943) provides a dichotomous key for This species can be readily distinguished from identifying M. anguillicaudatus from other the oriental weatherfish because it has a great Misgurnus species. Some of the characteristics number of fine surface scales covering its body he lists that are used in the key are that the scales rather than irregularly embedded scales (Rendahl 1934). Also, the caudal fin of M. These fish, like many other cypriniform fishes, mizolepis is greatly reduced in relation to its are generally considered r-selected organisms in body length in comparison with that of M. that they mature quickly, reproduce multiple anguillicaudatus. Although one specimen was times and produce a great number of offspring. found in Oregon, no other specimens have since Members of this species are sexually distinct and been collected there or anywhere else in the reproduce sexually. Males of the species mature United States, so it can be assumed at this point rapidly within a year and females mature within this related species has not established non- one or two years (Lei and Wang 1990). In their native populations (Tabor pers. comm.). native range, these fish spawn multiple times per year during a spawning season that lasts from Life history and basic ecology mid-April until mid-October. However, in established non-native populations in Indiana, Life Cycle and Reproductive Habits females with ripe ova were collected in mid- M. anguillicaudatus inhabits still water, June and based on other physiological characters shallow pools and near shore shallow water it appears that they had just started the breeding mudflat areas of lakes, rivers, streams, swamp, season (Simon et al 2006). This could indicate rice patties and ponds. In these environments it that these fish are altering their breeding season is commonly found burrowed into mud, silt, based on different environmental conditions in macrophyte beds or leaf detritus (Simon et al. their non-native ranges. 2006). In other areas where it has invaded, such Reproduction occurs at night in which the male as Hawaii, it has been found under mats of locates a female based on scent and wraps his honohono (Commelina diffusa) and California body around the female stimulating her to grass (Brachiara nuatica) (Simon et al. 2006). release a cloud of eggs that he rapidly fertilizes This species is primarily nocturnal, spending (Yamamoto and Tagawa 2000). The female most of the day burrowed into mud from which produces 1800-15500 eggs per batch with an it emerges at night to feed and mate. However, average survival of 2000 eggs per batch (Berg like their name would suggest, these fish 1949; Suzuki 1983). The eggs are small with a become extremely active right before periods of diameter of 800-850 m and are reddish in color severe weather due to changes in barometric with adhesive properties, however, are broadcast pressure and it is interesting to note that these into the water column upon conception (Suzuki fish were used by ancient Chinese scientists and 1983). Eggs hatch within 30 hours and larvae Victorian era Europeans to predict the weather remain in water column for a short period before (Sterba 1983). settling on the bottom (Wang et al 2008). By combining all of these reproductive characters, Berg (1949) was able to determine the minimum weatherfish devouring the eggs of endemic population doubling time for this species to be fishes, very little evidence has been shown to 1.4-4.4 years, which is fairly short for fish support this and none of the fish collected by species. A vast amount of much more thorough Tabor et al. (2001) had fish eggs in their gut information on the mating habits and cavities. development of M. anguillicaudatus can be found in Chinese literature sources, that the Environmental optima and tolerances author was unable to translate. Some of the characters that make the oriental weatherfish a very successful invader, is Feeding Habits its ability to tolerate and thrive in a very wide Oriental weatherfish are benthic range of temperature and oxygen conditions. omnivores that feed generally on insect larvae, Since M. anguillicaudatus occupies a natural snails, worms, ostracods, cladocerans, fish eggs, range that extends all the way from southern algae and detritus (Sterba 1983). Very little is Siberia to the northern Indochinese Peninsula, known about their feeding habits in their natural they have to be able to tolerate cold winters and range and most of the diet data comes from gut warm summers. In 1996, Logan et al. evaluated content analysis of invasive populations the thermal tolerances of individuals collected in elsewhere in the world. However, Kim et al. Clackamas County, OR by acclimating them to (1994) demonstrated that M. anguillicaudatus 18-20C for six months then the water readily and efficiently consume mosquito larvae temperature was lowered 2C daily until a and have successfully used them to control temperature of 2C was reached. At this mosquito populations in South Korea. Tabor et temperature, the fish were still alive, but al. (2001) found that in their invaded range in required prodding to elicit movement. This Washington, that their diets primarily consisted same study demonstrated that the fish were of crustaceans, such as: amphipods and easily able to tolerate abrupt temperature spikes cladocerans, as well as, chrionomids with from 6C to 18C and within 24h were observed minimal detritus and plant matter. However, in feeding again. Also, their thermal tolerances fit a study by Burchmore et al. (1990), non-native with the average annual temperature fluctuations fish in Australia were found with higher levels of the Snake, Willamette and Sacramento rivers of algae and detritus in their stomachs. Logan et in OR which range from 3.7C to 19.3C (Logan al. (1996) found that these fish did consume et al. 1996). Based on their presence in shallow mosquitofish, Gambusia affinis, fry as well as ponds in tropical regions, it can be assumed that commercially prepared salmon eggs in aquaria. they are also able to tolerate temperatures up to Although there are concerns of non-native and maybe over 30C. This wide thermal tolerance range means that this species is able to external environment allow these fish to survive over winter in many regions and may even be in very small bodies of still water and in hypoxic able to survive in iced over bodies of water swamp and still water environments. This (Fryhof and Korte 2005). means they can also inhabit areas of high In addition to their ability to tolerate a large turbidity and eutrophication and bodies of water thermal range, they are also able to survive in that are affected by algal blooms. low oxygen and hypoxic conditions. This ability These fish are found in freshwater is due in part to the fact that, like other basal environments; however, they have not been teleost fishes, such as, killifish and mudfish, evaluated for their ability to survive in brackish they are able to process atmospheric oxygen. or saltwater. In addition, they have not been They do this by taking air into their mouth and evaluated for their tolerance of variances in pH; diverting it into their anterior alimentary canal of however, since they have been found in stagnant their intestine. There the oxygen is diffused water, rice paddies and swamps, it can be over a membrane of dense capillary beds and is assumed they can inhabit low pH environs (Berg able to diffuse into their blood stream 1949).