160 



side of snout. No tubercles present at anterior end of snout. Numerous small tubercles on 

 lateral side of the head. 



Each scale of the 1 1 rows of breast scales bearing four to eight small tubercles along the 

 apical margin. Scales on the area between the breast scales also bearing tubercles. The re- 

 maining ventral area of body bearing no tubercles. No tubercles on all fins. 

 Coloration. 14-15 parallel and vertical dark bars present on side, from behind the gill 

 cleft to posterior part of caudal peduncle. Bars in front of insertion of dorsal fin longer 

 than those behind insertion. Juveniles (less than 25 mm standard length) lack vertical bars 

 but have one longitudinal stripe from the gill cleft to the caudal fin base. Some specimens 

 also bearing a few large speckles dorsally. A dark dorsal stripe present from nape to base 

 of caudal fin. 



Numerous melanophores are present on trunk, except ventral to lateral bars where mela- 

 nophores are absent or few. Breast region bearing melanophores in male. Dorsum dark, 

 with numerous melanophores, becoming paler on sides in spaces between lateral bars. 

 Head with numerous melanophores dorsally, laterally, and ventrally. Anterior part of 

 opercle bearing more melanophores than its surrounding. 



All fins bearing melanophores on rays and membrane. On pectoral fin, the first ray dar- 

 ker than others. Pelvic fin dark, evenly pigmented. Base of dorsal fin with a black patch, 

 and the rays with more melanophores than the membrane. Anal fin uniformly dark, but 

 base of fin bears very few melanophores. Base of caudal fin bearing more melanophores 

 than rest of the fin. 



Biology 



P. phoxinus inhabits flowing water, ponds, shallow lakes, and margins of deep lakes, such 

 as Lake Baikal (Berg 1949). It lives on various bottoms, but prefers stony substrates (Frost 

 1943). Schools of hundreds of individuals sometimes occurs in shoal area (Frost 1943, 

 Partridge 1980). Fish species associated with P. phoxinus include freshwater eel [Anguilla 

 anguilla (L.)], salmon (Salmo salar L.) (Frost 1943), stickleback (Gasterosteus aculeatus 

 L.), and Noemachielus barbatulus (L.) (Dauod et al. 1985). 



The food mainly consists of copepods, filamentous algae and diatoms. P. phoxinus also 

 eats insect larvae (Frost 1943). Dauod et al. (1985) recognized 12 categories of food items 

 for the species: surface insects, mollusca, trichopteran larvae, trichopteran pupae, clado- 

 cera, copepoda, chironomid larvae, chironomid pupae, ephemeropteran nymphs, other 

 larvae, Gammarus and "chance" food. According to these authors, the diet composition 

 changes seasonally. For instance, the most important food items early in year were chiro- 

 nomid larvae, mollusca, and trichoptern larvae. These foods were replaced by daphnia and 

 surface insects in May. 



The species reaches its mature at 35-45 mm standard length in about their second year 

 (Dauod et al. 1985). The breeding season varies from early April to September depending 

 partly on latitude. Prior to spawning, large school of adults migrates to smaller stream ha- 

 ving cooler water (Bade 1902, Frost 1943). The school might be concentrated on an ap- 

 proximately circular surface of about 30 cm diameter, and 1.5 cm thick layer. Individuals 



