Caldarone et al.: Nonlethal techniques for estimating responses of postsmolt Salmo solar to food availability 
259 
Table 1 
Sampling schedule for Atlantic salmon ( Salmo salar ) postsmolts reared at 12°C under three feeding regimens (fed; fasted; fasted 
then refed) in order to obtain a range of nutritional condition and growth rates. Nonlethal condition indices (Fulton’s condition 
factor \K\ and bioelectrical impedance analysis [BIA] measures) and two measures of nutritional condition (wet-weight based 
growth rate and proximate body composition) were determined for each fish. The refed group was fasted for 11 days and then fed. 
Numbers listed are number of fish sampled. 
Sampling day and feeding regimen 
Day 0 
Day 3 
Day 7 
Day 11 
Base-line 
Fed 
Fasted 
Refed 
Fed 
Fasted 
Refed 
Fed 
Fasted 
Refed 
Fed 
Fasted 
Refed 
Weight, length 
5 
24 
24 
22 
4 
4 
0 
4 
4 
0 
4 
4 
22 
(Fulton’s K) 
BIA measures 
5 
24 
24 
0 
4 
4 
0 
4 
4 
0 
4 
4 
0 
Proximate body 
5 
0 
0 
0 
4 
4 
0 
4 
4 
0 
4 
4 
0 
composition 
Sampling day and feeding regimen 
Day 15 
Day 19 
Day 23 
Day 27 
Fed 
Fasted 
Refed 
Fed 
Fasted 
Refed 
Fed 
Fasted 
Refed 
Fed 
Fasted 
Refed 
Weight, length (Fulton’s K) 
4 
4 
5 
4 
4 
5 
4 
4 
5 
0 
0 
7 
BIA measures 
4 
4 
5 
4 
4 
5 
4 
4 
5 
0 
0 
7 
Proximate body composition 
4 
4 
5 
4 
4 
5 
4 
4 
5 
0 
0 
7 
Eco-Systems, Inc., Apopka, FL). Twenty-five days after 
the initial seawater transfer, when the now postsmolts 
appeared to be acclimated and feeding well, the experi- 
ment commenced (day 0). 
Throughout the experiment, water temperature in 
each tank was recorded hourly with a HOBO® data log- 
ger (Onset Computer Corp., Bourne, MA), and ammonia 
levels and salinity were tested weekly. Water tempera- 
tures averaged 12.0°C, standard deviation (SD) = 0.2; 
salinity averaged 31 ppt, SD = 1; and the photoperiod 
was 15 hours of light to 9 hours of dark. Two-thirds 
of each tank surface was covered with black plastic 
to provide a low-light refuge, and the remaining third 
was exposed to overhead fluorescent lighting covered 
with red plastic. All experiments were conducted in 
accordance with guidelines established by the Institu- 
tional Animal Care and Use Committee (IACUC) at the 
University of Rhode Island. 
Sampling protocols 
Day 0 sampling On day 0, five fish were randomly 
selected and sacrificed to provide baseline body compo- 
sition data. To obtain a range of nutritional condition 
levels, all remaining postsmolts were subdivided into 
three different feeding treatments (tanks); fed, fasted, 
and fasted then refed. The fed treatment (re = 24) was 
continually fed, the fasted treatment (re =24) received 
no food, and the fasted, then refed treatment (re =22) 
received no food for 11 days followed by feeding for 
16 days. Individuals were anesthetized with buffered 
MS-222 (150 mg/L) in chilled (12°C) seawater, blotted 
dry, measured for initial weight (wet weight, WW, near- 
est 0.1 g) and fork length (FL, nearest 0.1 cm), and the 
PIT tag number and any gross external abnormalities 
were noted. BIA measurements were taken on all fish 
assigned to the fed and fasted treatments. Fish assigned 
to the fasted, then re fed treatment had their fork length 
and wet weight recorded at the start of their fasting 
(day 0), and again on day 11 when they were fed for the 
remainder of the experiment. Total handling time per 
fish for wet weight, fork length, and BIA measurements 
was no more than 30 seconds. 
During daylight hours, fish in the fed treatment and 
refed group were provided freeze-dried krill ad libitum 
from a belt feeder. On days fish were sampled, no food 
was provided until after sampling was completed (-1200). 
Days 3-27 sampling In order to determine the response 
time of BIA measures and K to the three feeding treat- 
ments, and to construct predictive equations for body 
composition, fish were sampled and sacrificed every 
three to four days over a 23-27 day period. On day 3 
and every 4 days thereafter, 4 fish each from the fed 
and fasted treatments were sacrificed. On day 15 and 
every 4 days thereafter, 5 fish from the refed group were 
sacrificed and sampled, except on the final day when 7 
fish were sacrificed (Table 1). 
