There is little info on F-1 crosses in colder climates. Flas don't do well in colder climates. I will check some more as it has been a while since the last look.

Try this

Responses of Northern, Florida, and Hybrid Largemouth Bass to

Low Temperature and Low Dissolved Oxygen



GARY J. CARMICHAEL' AND

J. HOLT WlLUAMSON2

U.S. Fish and Wildlife Service

San Marcos, Texas 78666, USA

COLLEEN A. CALDWELL WOODWARD* AND

J. R. TOMASSO4

Aquatic Station

Southwest Texas State University



Low Temperature

Largemouth bass treatment groups that were

cooled slowly and then held at about 2°C for 5 d

demonstrated differing rates of mortality (Figure

1). Mortalities were significantly higher (chi-square)

among Florida fish (48%) than for other strains,

4-5% for F x N fish and nil for N x

F fish. All fish in water that was cooled from 21

to 1°C, held at that temperature briefly, and then

warmed to 21 °C in 90 min survived and fed normally

within 24 h. Feeding behavior was normal

as temperatures dropped to 13°C, fish fed slowly

between 12 and 6°C, and no feeding by any fish

was observed at temperatures below 6°C.

Largemouth bass treatment groups that were

cooled slowly and then held at about 2°C for 5 d

demonstrated differing rates of mortality (Figure

1). Mortalities were significantly higher (chi-square)

among Florida fish (48%) than for other strains,

4-5% for F x N fish and nil for N x

F fish. All fish in water that was cooled from 21

to 1°C, held at that temperature briefly, and then

warmed to 21 °C in 90 min survived and fed normally

within 24 h. Feeding behavior was normal

as temperatures dropped to 13°C, fish fed slowly

between 12 and 6°C, and no feeding by any fish

was observed at temperatures below 6°C.

Dissimilarities in response to low-temperature

challenge is expected between fishes whose native

ranges differ latitudinally. Previous studies have

indicated differences in temperature response between

the northern and Florida subspecies of

largemouth bass (Cichra et al. 1980; Guest 1982,

1985)—as well as similarities (Guest 1980). Direct

comparison of the four strains enabled us to show

that both subspecies and their hybrids tolerated

brief exposure to low temperatures, but that survival

after prolonged exposures was better in N x

N and N x F strains than in F x F and F x N

strains (female first). The responses of both hybrids more closely

resembled the N x N than the F x F fish. Strain

contamination (hybridization) could have significantly

affected previous studies and accounted for

the variable results among those studies. Our results

showed clear-cut differences in mortality due

to cold exposure, and we speculate that exposure

to low temperatures might result in additional response

differences among largemouth bass strains.

For instance, after exposure to cold, the strains

may have different responses to a secondary

stressor or to diseases; for example, exposure to

low temperatures has been shown to alter the response

of largemouth bass to net-confinement

stress (Carmichael et al. 1984b).


Last edited by ewest; 07/04/08 10:15 PM.