Southeast Asian Fisheries Development Center Aquaculture Department
SEAFDEC/AQD Institutional Repository http://repository.seafdec.org.ph
Institutional Reports Quarterly Research Reports
1979
The effect of various salinity levels and stocking density manipulation methods on the survival of milkfish fry (Chanos chanos Forsskal) during storage
Quinitio, Gerald F.
Aquaculture Department, Southeast Asian Fisheries Development Center
Quinitio, G. F., & Juario, J. V. (1979). The effect of various salinity levels and stocking density manipulation methods on the survival of milkfish fry (Chanos chanos Forsskal) during storage.
SEAFDEC Aquaculture Department Quarterly Research Report, 3(4), 5–10.
http://hdl.handle.net/10862/2357
Downloaded from http://repository.seafdec.org.ph, SEAFDEC/AQD's Institutional Repository
T h e e f f e c t o f v a rio u s s a li n i t y le ve ls a n d s to c k in g d e n s it y m a n ip u l a t io n m e th o d s o n t h e s u rv iv a l o f m il k f is h f r y (C h a n o s c h a n o s F o r s s k a l) d u r in g s to ra g e
G e r a ld F . Q u in it io a n d Jesus V . J u a r io
The m ilkfish fr y industry has long been existing in the Philippines. F ry dealers fro m d iffe re n t parts o f the co u n try have developed th e ir own techniques o f storing and feeding fr y before they are sold to fishpond owners. Consequently, d iffe re n t methods in the m anipulation o f stocking density during storage are now being em ployed; feeding has never been standardized and the salinity o f the water suitable fo r storing fry has n o t been determ ined. A n to n io and Manacop (1956) obtained a survival o f 99.0% o f fry stored fo r tw o weeks in freshwater and a survival o f 83.3% fo r 11 days in seawater. The com m on practice, however, is to store fr y in water w ith low salinity (approxim ately 18-20 ppt). Generally, m ortalities ranging fro m 3% to 10% (personal interviews) occur during the period o f storage w hich w ould last fo r, at most, tw o weeks. It is n o t know n, however, w hat causes the m o rta lity . This may be due to stress because o f im proper handling during collection, sorting, counting and transport (Blanco and V illa d o lid , 1939; Carbine, 1948; A n to n io and Manacop, 1956; PCARR, 1976); overcrowding and unfavorable w ater co n d i
tions (A n to n io and Manacop, 1956), o r even to in su fficie n t and unsuitable feed (R o n q u illo and V illam eter, 1957).
To date, there is no standardized method o f storing m ilkfish fr y , although there are a number o f publications describing the d iffe re n t practices o f the fr y industry concerning co lle ctio n , trans
p o rt and storage (Blanco and V illa d o lid , 1939; Carbine, 1948; Mane et al., 1952; V illa lu z , 1953;
PCARR, 1976; Librero et al., 1976 a and b; and S m ith , 1978). C onsequently, a study has been conducted w ith the ultim ate objective o f developing and standardizing a method o f storing m ilkfish fry such th a t m o rta lity is very much reduced. S pecifically the study aims to determine the effect o f various salinity levels and stocking density m anipulation methods on the survival o f m ilkfish fr y during storage.
The fry used in the experim ent were bought fro m one fr y concessionaire at H a m tik, A n tiq u e . These have been stored fo r tw o to three days w ith o u t feeding. Upon arrival, the fr y were counted while predators and other accompanying species were sorted out. T o avoid stress, the sa lin ity o f the original w ater was gradually changed to the desired salinities. The fr y were acclimated to the experimental set-up fo r one day. The fishes had an in itia l mean to ta l length o f
13.65 + 0.73 mm and in itia l mean w et weight o f 6 .9 8 ± 2 .4 0 mg.
In this study, w h ite plastic basins having 11.4 cm depth and 29.2 cm inside diameter were used fo r fr y storage. T o fo llo w closely the practices o f fry dealers, the containers were n o t p ro vided w ith aeration. The containers, covered w ith wooden slats, were placed on to p o f each other to save space. This arrangement provides free exchange o f air in between containers.
The d iffe re n t sa lin ity levels used were: 8 p p t; 16 p p t; and 32 p p t, w hile the d iffe re n t stocking density m anipulation methods were the fo llo w in g :
I . The same stocking density was maintained during the whole storage period.
Day 1 2 3 4 5 6 7 8 9 10 11 12 13 14
366 fr y /L
I I . The fry in every container were divided equally in to tw o groups after three days o f storage and the stocking density o f 183 fr y /L was maintained u n til the end o f the storage period.
Day 1 2 3 4 5 6 7 8 9 10 11 12 13 14
366 fr y /L 183 fr y /L
183 fr y /L
I I I . The number o f fr y in every container was divided equally in to tw o groups after every three days w ith in the firs t 10 days and the volume o f w ater was adjusted to attain the right stock
ing density per u n it volum e; thereafter, the new stocking density was maintained till the end o f the storage period.
Day 1 2 3 4 5 6 7 8 9 10 11 12 13 14
336 fr y /L
183 fr y /L
9 1 .5 fr y /L
45.75 f r y /L 45.75 f r y /L
91.5 45.75 fr y /L
fr y /L 45.75 fr y /L
183 fr y /L
91.5 fr y /L
45.75 fr y /L 45.75 fr y /L 91.5
fr y /L
45.75 f r y /L 45.75 fr y /L
The fr y were fed once a day w ith hard-boiled chicken egg y o lk blended w ith w ater to im part a m ilk y consistency (6 g o f hard-boiled egg y o lk per 100 m L o f freshwater). F o r every 6,000 fry , 45 m L o f freshly prepared feed were given.
A p p ro x im a te ly 3 /4 o f the water was changed every m orning. A ll the feces, excess feed and dead fr y were removed to prevent deterioration o f w ater q u a lity . M o rta lity was recorded tw ice a day.
Fig. 1 . D a ily mean percentage survival, level o f dissolved o xyg e n and p H o f th e d iffe r e n t sto cking d e n s ity m a n ip u la tio n m ethods at 8 p p t s a lin ity level.
Fig. 2 . D a ily m ean percentage su rvival, level o f dissolved o xyg e n and p H o f th e d iffe re n t stocking d e n s ity m a n ip u la tio n m etho d s a t 1 6 p p t s a lin ity level.
Fig. 3 . D a ily m ean percentage survival, level o f dissolved o x y g e n an d p H o f th e d iffe r e n t stocking d e n s ity m a n ip u la tio n m ethods at 3 2 p p t s a lin ity level.
in body w eight did n o t d iffe r significantly (P>.05) at d iffe re n t salinity levels o r at d iffe re n t stock
ing density m anipulation methods. Moreover, a significant interaction between salinity and stocking density m anipulation method could not be statistically demonstrated. The highest survival rate was 97.8% at stocking density m anipulation I w ith 8 p p t while the lowest was 95.5%
also at stocking density m anipulation I w ith 32 ppt. Increase in length, however, differed signi
fic a n tly (P < .0 5 ) at d iffe re n t s a lin ity levels; in a d d ition , a significant interaction could be statis
tic a lly demonstrated. Increase in length was fastest at: a) stocking density m anipulation I at 16 p p t; b) stocking density m anipulation II at 8, 16 or 32 p p t; and c) stocking density m anipula
tio n III at 8 or 16 ppt.
F rom the results o f this study, it is evident th a t there is no need to reduce the sa lin ity o f the w ater used in storing m ilkfish fr y in order to attain higher survival as com m only believed. S u ffi
cient fo o d and maintenance o f good water q u a lity are more im p o rta n t than salinity fo r higher survival o f fr y d u rin g storage.
L ite ra tu re C ite d
A n to n io , H.C. and P.R. Manacop. 1956. A prelim inary longevity test o f bangos fry in storage.
P hilipp. Journ. Fish 4 (1 ): 119-131.
Blanco, G.J. and D .V . V illa d o lid . 1939. Fish-fry industries o f the Philippines. P hilipp. Journ.
Sci. 6 9 (1 ): 69-100.
Carbine, W .F. 1948. Bangos culture in the Philippines. Prog. Fish-Cult. 10(4): 187-197.
L ib re ro , A .R ., S.P. D izon, A .G . T id o n , P.G. Ramos, and R .L. Alzona. 1976a. Fry Gathering Patterns, Costs and Returns and Socio-economic C onditions o f F ry Gatherers in the P h ilip pines. Res. paper series No. 1. SEAFDEC-PCARR Research Program, Los Banos, Laguna, Philippines. 123 pp.
Librero, A .R ., S.P. D izon, A .G . T id o n and R.L. Alzona. 1976b. Patterns o f F ry Purchase and Scale in the Philippines: A S tudy o f F ry Concessionaires and Dealers. Res. Paper series No. 3. SEAFDEC-PCARR Research Program, Los Banos, Laguna, Philippines. 124 pp.
Mane, A .M ., D .K . V illa lu z and H.R. Rabanal. 1952. C ultivation o f fish in brackish and estuarine waters in the Philippines. A H andbook on Philippine Fisheries: 100-110.
PCARR. 1976. The Philippine Recommends fo r Bangos 1976. P hilippine Council fo r A g ric u l
ture and Resources Research. 41 pp.
R o n q u illo , I . A . and E. V illam ater. 1957. Observations on a rtific ia l feeding o f bangos fr y , Chanos chanos (Forsskal). Philipp. Journ. Sci. 5 (2 ): 103-111.
S m ith, I.R. 1978. A n Econom ic Analysis o f the Structure and Performance o f the M ilkfish (Chanos chanos) Fry In d u stry in the Philippines and Related Aquaculture Development Policies. A dissertation subm itted to the Graduate D ivision o f the U niversity o f Hawaii.
307 pp.
V illa lu z , D .K . 1953. Fish Farm ing in the Philippines. Bookman, Inc., Manila. 336 pp.
