North Carolina Sea Grant NC State University Box 8605 Raleigh, NC 27695-8605

Improved Production of Hybrid Striped BassFingerlingsThrough Better Feeding Practices

Most producers feed Phase II hybrid striped bassfingerlings three to four times per day in an effort tooptimize growth and promote size uniformity of thepopulation. However, fish farmers must consider theeconomic trade-off between the benefits of frequentfeeding and the cost of labor, fuel, and wear onmachinery such as tractors and feed blowers.

Fewer daily feedings would be desirable becausetime is a valuable resource on a fish farm. Time spentfeeding is not available for other activities.

Extreme differences in size among hybrids arelargely caused by the aggressive feeding behavior ofa few fish that intimidate others in the competition foravailable food. Underfed fish grow slowly, eventuallyreaching a point when they cannot regain a normalweight even after their feed ration has been in-creased.

These "runts" are too small to be stocked intofoodfish ponds unless they are stocked with fish ofsimilar size. Difficult to sell, they have a negativeimpact on profitability of fingerling production.

Frequent feeding of fingerling ponds allows less-aggressive fish to feed after the dominant fish are full,leading to more uniform size distribution and agreater percentage of fingerlings suitable for stockingfoodfish ponds.

To optimize production and improve the econom-ics of Phase II fingerling production, producers needa thorough understanding of the effects of differentfeeding practices on size distribution and overallproduction of hybrid striped bass fingerlings.

Feeding Option5Time of DayFish feed by sight and are normally fed during

daylight hours. Experienced fishers have observedthat fish feed more actively during the early morning

or late evening hours when the light intensity islower. However, fish ponds experience dailyfluctuations of dissolved oxygen (DO), with con-centrations are lowest at dawn. Low DO concen-trations may stress the fish, leading to reducedfeeding activity. Fish respiration increases soonafter feeding. DO concentrations begin to declineafter sunset. Therefore, feeding during the lateevening will increase the demand for oxygen at atime when the DO concentrations are falling.

FrequencyFeeding once per day is the least labor-inten-

sive option, but such fish may not be able to eatenough each day for optimum growth. Excessfeeding is wasteful, expensive and contributes todeterioration in water quality. As mentionedabove, frequent feeding is thought to reduce sizevariation in hybrid ponds. However, frequentfeedings are time-consuming and increase ma-chinery costs such as fuel, and maintenance/repairof tractors and feed blowers.

Ca5e Study with Pha5e" Fingerling5To illustrate the effects of feeding on size

distribution and overall production, let's look at theresults from a controlled-feeding study done at theTidewater Research Station in Plymouth, NC,where different feeding times and frequencieswere studied.

Study MethodsPhase II hybrid striped bass (Morone chrysops

x M. saxatilis), with an average weight of 1.5 geach, were stocked at a density of 16,000 fish/acre. Ponds were fed according to the followingfeeding regimes:

Table 1.Summary of production variables (means +/- SE) for Phase IIhybrid striped bass fingerlingsfed daily at different frequencies during a 120-day study. Means followed by the same letter are notstatistically different.

* Once/day dawn (within 1-h of sunrise),* Once/day dusk (within 1-h of sunset),* Twice/day (dawn and dusk), and* Four times/day (dawn, 10 am, 2 pm, dusk)Daily feed ration was calculated as a percent of

body weight and either given all at one feeding ordivided equally between the different feeding times,depending on the treatment. Feeding stopped whenresearchers observed that fish were not activelyeating. The amount already applied to the pond wasrecorded.

Ponds were harvested after five months and

samples of 300 fish from each pond were selected.Individual lengths and weight were measured oneach fish for a total of 900 fish per treatment.

Once per Day: Morning versus EveningThe smallest fish were those fed once daily in

late evening. The morning feed treatment had ahigher percentage of larger fish than the once perday/evening treatment - 46 percent versus 34percent - so feeding once per day at late eveningcaused a narrower distribution of mostly smaller fishthan the morning feeding treatment (Figure 1).

Based on these results, feeding in the morningis preferable to an evening feeding in hybridstriped bass fingerling ponds when ponds are fedonly once per day.

Feeding Frequency:Onceversus Twiceor MoreFish that were fed only once per day either in

the early morning or late evening were significantlysmaller than those that were fed at least two timesper day (Table 1).

Fish fed two or more times per day had higheroverall production and much greater averageweights than those that received feed only onceper day. Less than half the fish in the once/daytreatments were larger than 80 g - or five to sixfish per pound - at the end of the growing sea-son. Meanwhile, more than two-thirds of the fishthat were fed at least twice per day were largerthan 80 g (Figure 1).

Clearly, there is a significant improvement inoverall production - and a more favorable sizedistribution - when feeding frequency is increasedfrom once per day to at least twice per day.

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FeedDailyFeeding Production Survival AVf1tWJe ConversionFrequency (kgha) (percenIage) Weight (g) (wtfeedapplied

wt fish produced)

1 / day, dawn(within 1 hour of 2528+/- 509 ab 82.0 +/- 9.6 a 78.5 +/-6.8 a 1.83 +/-0.31 asunrise)

1 / day dusk(within 1 hour of 2153 +/- 502 a 82.0 +/- 4.4 a 67.0 +/- 15.5 a 2.02 +/- 0.40 asunset)

2 / day 3058 +/- 556 be 73.7 +/- 6.3 a 109.0 +/-21.5 b 1.83 +/- 0.23 a(sunrise and sunset)

4 / day(Sunrise, 1000 h, 3638 +/- 441 e 81.3 +/- 9.1 a 112.7 +/- 3.2 b 1.57 +/- 0.19 a1400 h, sunset)

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Feeding Frequency: Twice ver5U5 Four Tme5Although the percentage of fish larger than 80 g

is higher in the four times/day treatment than thetwo times/day treatment - 74 percent versus 69percent - this difference is not statistically signifi-cant.

When the largest category of fish (greater than140 g each) are excluded from the data, the two andfour times per day treatments produced an almostidentical rate - 52 percent vs. 54 percent - of fishbetween 80-140 g. Therefore, very little benefit isgained by feeding more often than twice per day.

A publication of theUniversity of North CarolinaSea Grant College Programpursuant to National Oceanicand Atmospheric Administra-tion Award No. NA86RG0036

Conclusion

Phase II hybrid striped bass production is opti-mized by feeding twice per day.

More frequent feedings do not lead to improve-ments in production and are more costly and timeconsuming.

Feeding only once per day is the least timeconsuming option, but results in a high percentageof undersized fish.

- H.V. DanielsNorth Carolina State University

8mNorthCarolina

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