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COSEWIC Assessment and Update Status Report on the Banded Killifish, Newfoundland population in Canada

Biology

General

Of the three Newfoundland populations sampled, the Loch Leven population had the largest mean total length at 91.9mm (56.5-106.3mm) while the Indian Bay population averaged 88.8mm (68.6-128.4mm) and Freshwater Pond population 73.2 mm (Chippett In prep.). In previous studies Banded Killifish adults usually ranged from 6-8cm (Cooper 1983). The 12.8cm record from Indian Bay is likely the largest recorded length for this species. Scott and Crossman (1973) indicated that a Banded Killifish measuring 11.4cm from Lake O’Law in Nova Scotia was the largest record prior to the Indian Bay record.

Carlander (1969) reported that individuals reach maturity at 1+ years and at a total length of about 6cm. The minimum size for mature females from the Newfoundland populations was noted to be 5.6cm (Chippett In prep.).


Reproduction

Banded Killifish are plant spawners and females release eggs attached to individual adhesive threads that adhere to aquatic vegetation once released. Males release milt and fertilize the eggs as they hang from the female papilla in clusters of 5‑10 eggs (Richardson 1939). Spawning is indicated as taking place in April to May with a temperature of 21°C being preferred (Carlander 1969) while other spawning observations have been documented at 23°C (McAllister and Coad 1974).

Banded Killifish in the Indian Bay watershed were observed exhibiting spawning behaviour in late June through to the middle of August when water temperatures reached between 19-23°C, most often in association with pondweed species of the genus Potamogeton.  Males undergo a drastic color change when spawning, developing a bright blue patch near the anal fin (Chippett In prep.; Scott and Crossman 1973). The lower portion of the body, including the area around the anal fin, transforms into a brilliant iridescent blue color. In areas where the water is dark or murky, particularly those with mud substrates like the Indian Bay watershed, the males can be identified by quick darting movements made obvious by the blue coloration against the dark substrate (Chippett In prep.). This color change is much more evident in the wild than in captivity.

Eggs taken from female fish in the Indian Bay watershed in late July were slightly larger (0= 2.2mm) than the 2.0mm reported by Cooper (1936) and large females contained as many as 420 eggs as compared to the 250 reported by Carlander (1969) (Chippett In prep.).


Physiology

Banded Killifish are tolerant of low oxygen levels and a wide range of temperatures (Scott and Crossman 1973; Houston 1990). Carlander (1969) observed Banded Killifish at 38.3°C while Rombough and Garside (1977) reported 34.5°C as the upper incipient temperature limit for this species. In Newfoundland, Banded Killifish spawning was observed at water temperatures of 22-24°C in the shallows and abundance of Fundulus diaphanus in fyke net catches was strongly related to water temperatures (Chippett In prep). These observations concur with those of Melisky et al. (1980) who found that Banded Killifish in Pennsylvania had a preference for waters of approximately 28.6°C and that fish in Nova Scotia prefer the lower temperature of 21.0°C. Banded Killifish move into deeper sections of lakes during late fall and winter before emerging into the shallows after the ice melts in April or May (J.G. Godin, pers. comm.).

Banded Killifish are euryhaline but usually inhabit freshwater streams and lakes, rarely existing in brackish or marine waters (Fritz and Garside 1974, 1975). This is true of the Newfoundland populations (Chippett In prep.). Fundulus diaphanus is tolerant, however, of salinities in excess of 20ppt, making dispersal through salt water possible (Griffith 1974). Underhill (1986) states that the Banded Killifish may have a maritime origin from the Atlantic provinces, but as indicated above, this is debatable. The populations on the south and west coasts appear close enough to make migration between the Newfoundland populations possible, but, such movement is undoubtedly small in scale (Chippett In prep.). The population on the northeast coast in the Indian Bay watershed may have been the result of an introduction, as anecdotal evidence by local anglers suggests; anglers from the Maritime provinces using minnows (live-bait) have traditionally fished in Backup and Third Ponds (W. Norris, pers. comm.). It is common for both Banded Killifish and Fundulus heteroclitus to be sold as live-bait in Nova Scotia and New Brunswic (A. Curry, pers. comm.).


Movements/Dispersal

Banded Killifish were observed in shallow, sheltered areas during the day in areas with abundant, dense, submerged aquatic vegetation, with very little observed migration during the daylight hours. However, data from fyke nets set in a variety of habitat types indicated a greater abundance of killifish in deeper, more exposed rocky areas suggesting nocturnal movements away from and/or between vegetated areas (Chippett In prep.).

The Banded Killifish in the Indian Bay watershed occupy a very restricted range. It is likely that the species has had little success in dispersing throughout the watershed due to long stretches of deep, open water where brook trout and Atlantic salmon predation would be substantially higher than would be the case in the weedy shallows (Chippett In prep.).


Nutrition and Interspecific Interactions

Keast and Webb (1966) indicated that despite the superior position of the mouth, Banded Killifish feed in all levels of the water column. Smaller individuals eat chironomid larvae, ostracods, cladocerans, copepods, and small quantities of amphipods and some flying insects while larger individuals feed on the aforementioned species and also take Odonata and Ephemoptera nymphs, molluscs, tubellarians, and small crustaceans (Keast and Webb 1966; Baker-Dittus 1978). While specific information on Banded Killifish feeding is not available for Newfoundland populations, specimens taken from the Indian Bay watershed did contain a high proportion of chironomid larvae (personal observations).

Fundulus diaphanus is a forage fish for larger species like Atlantic salmon (Salmo salar), brook trout (Salvelinus fontinalis) and American eels (Anguilla rostrata) and is also preyed upon by Belted Kingfishers (Megaceryle alcyon) and American Mergansers (Mergus merganser) (White 1953,1957; Scott and Crossman 1973). However, adult Banded Killifish are often observed in association with large schools of young brook trout of similar size and are caught in fyke nets with brook trout, American Eels (Anguilla rostrata),Three-spined Sticklebacks (Gasterosteus aculeatus), Atlantic Salmon adults and parr, and Rainbow Smelt (Osmerus mordax). Predation in Loch Leven is likely extremely high from the large population of American Eels in this area as indicated by the numbers in fyke net catches (Chippett In prep.).


Behaviour

Schooling

Banded Killifish adults (3-4 yrs) were usually observed in small schools of 3‑6 individuals while younger fish (1-2+ yrs) were most often recorded in schools of 8‑12 individuals. Schools remained in the same general area for long periods of time. Smaller fish use edges of areas of still water with abundant riparian vegetation for shelter while the adults (3-4 yrs) were found in more open areas, particularly at the outflows of streams and brooks (Chippett In prep.). Schooling likely plays a role in predator avoidance and feeding (Keast and Webb 1966; Godin and Morgan 1985).

Spawning

Banded Killifish in the Indian Bay watershed were observed exhibiting pre-spawning and spawning behaviour in late June through to the middle of August when water temperatures reached between 19-24°C (Chippett In prep.). As observed by Richardson (1939) males selected breeding areas in quiet weedy pools and defended these areas vigorously after which males and females of similar size paired off. The intense circling bouts between rival males were also observed to the extent of the pursued males being “forced” out of the water (personal observations).