Growth and Production of the Balsas Catfish, Ictalurus ... - UAEM

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Jooma1 01Aquaculture in the Tropics May 2002 129 dissolved oxygen (YSI 57 oxygen meter), pH (Coming M·106 pH meter), conduclivity (Conductivimeter YSI 33), Secchi visibility and total dissolved solids were measured once a month according to Boyd (1996). Daily water exchange was adjusted to maintain Secchi visibility above 30 cm and measured with a meter in the experimental pond. Water quality data representa only lhe surface water. Fish were fed at 6% of lheir metabolic weightlday with catfish cornmercial food (Silver cup), made in Mexico by El Pedregal Foods Cornpany (38% protein, 21.4% lipid, 20.95% carbohydrate, 1.84% fibre, 11.58% ash contenl in a pellet size ot 9.3 mm). Quantity 01 rooc was readjusted' every 2 weeks based on a growth rate estimáte. Cat1ishwere fed 6 days a week, dürin~ the moming (0.8:00 h) and the evening (18:00 h). The w = aL lunction was used to obiain the weight and length retatíonship (Weatherley I 1972). Physico-chemical data, total lenglh and total tresh weight were submitted to statistical descriptive and Box plot statistical analysis using the STATISTICA version 5.0 package (1997). RESULTS Water temperature, dissolved oxygen, pH, totai dissolved solids and conductivity parameters were measured frcm March 1994 lb February 1995 (Fig. 1). The data indicates that, during this period pH values ranged between 7.6 to 9.0; dissolvad oxygen 4.3 to 5.8 mgll; total dissolved solids 476 to 600 mgil, and conductivity from 560 to 800 umbos/cm. The water temperature and pH were the most stable parameters alon9 the growth periodo Total dissolved solid andconductivity showed seasonal fluctuations in relation to the availability ot water source. The concentralions of these parameters were reduced towards the end of year (October to December); the dissolved oxygen on the other hand showed an increased tendency trorn June until the end ot the experiment. The method for rearing the species has been developed in warm-water pond farms, in the southem part of Mexico, where a long (280 to 320 days) and warm (25 to 35·C) season contributes to their rapid growth. With respect to these abiotic tactors; water quality appeared to be favourable for ñsh production. Growth and production estimates are shown in Table 1. The highest growth rate were observed from June to January (Fig. 2) at water temperatures above 30·C. Total weight gain per fish in a twelve-month period was of 390 g. The results iIIustrate the advantages ot raising the species in warm-water tish farms throughout the year, since as good growth-rates were even recorded during the winter. The maximum growth for the smallest fish took place at 29 to 3S·C, whereas the biggest fish grew best at 28 to 30·C. Specific growth rate decreased from a maximum 1 ~
__ ·..:J!WIlU ::~. .." .. :~,':' .. .·:'iI¡!9l! (5 CI) CI) e 40 r- o°e 30 ¡..... Ií' ~ I E 20 1 CI.I • C. . ~ 10 ~ I o .t-. 700 600 . 500 400 '._300 ( ~···----T-·- 'ro '1"-'" 7 i ~ 6 §. 5 c: I I ~ 4 ~ I o 3 I I -e 41 I > _ ..... _- --- 1000 200 1 1 100 I o M A M J J A' 5 o N o E F' I 'O In IIJ C3 2 o - l.' 5 > CI) .- o Ü.r. ::J E ~ c: o lo. o u l> .- E- .- - ~ 800 600 400 I ." . ", ~ 1 200 1\ o L--.__~~~~ __ ~~ ~ MAMJ JASONDFF Ag. 1: Water temperature. total dlst.olved soRd and conductlvlty values 01 tho pond water. The vaíues glveo are data comblned 1rom Ihree . repllcat,,!'. r tII g g ~ 5l. ). 1 •• !5' S CI> f E -cN 8:-.l
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Growth and Production of the Balsas Catfish, Ictalurus ... - UAEM

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