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Previous issue date: 2007-12-05 === Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico === The aim of this study was to test the sediment preference of L. vannamei shrimp. It was observed shrimp visit frequency, swimming and burying behaviour at different sediment compositions for 24h. Juvenile (0.93 ? 0.29g) and sub-adult shrimps (10.0 ? 1.18g) were obtained from the aquaculture
station at Universidade Federal Rural do Semi-?rido UFERSA, and held in a plastic tank (water volume 500 L) supplied with aerated water and kept at constant temperature, pH, and salinity. Shrimp was fed by commercial shrimp dry food. The experimental substrates were composed by A: medium sand +
thick sand + very thick sand + gravel; B: very fine sand + fine sand; and C: silt + clay. Thus, six different substrate combinations were tested: A, B, C, A+B, A+C, B+C. To test preference, it was used a cylindrical tank (40 l) divided into six
differently substrate compartments. A single shrimp was introduced each tank and the frequency at which this shrimp visited each compartment was recorded over a 24h study period. It was tested 54 shrimp (18 sub-adult males, 18 subadult females and 18 juveniles). For each trial, sediment and water were changed to avoid pheromones and residues influence. Shrimp were weighted and sub-adults were divided by sex: males present petasma and females present thelycum. Data were collected on the experimental day at 19:30; 20:30; 00:30; 1:30; 05:30; 06:30; 13:30 and 14:30 h. At each time point, shrimp were observed for 20-min periods, in which we noted down which compartment the
shrimp was occupying at 2-min intervals. Thus, for each period we had eleven observations (88 observations per day). For observations at night, it was used dim red light that did not affect shrimp behaviour. At each 20-min period, it was
observed visit frequency in each substrate, if shrimp was burred or not or if it was swimming. There was not significant difference between light and dark burry activity for females. Swimming activity was significantly higher at night,
mainly at 00:30 and 01:30 h. All L. vannamei shrimp showed preference for sediment B. This animal presents cyclic activity, spends the day light period buried and swims at night === Este trabalho visou caracterizar a freq??ncia de visita e enterramento como prefer?ncia de sedimento em diferentes sedimentos e a atividade natat?ria dos camar?es Litopenaeus vannamei durante 24 horas. Camar?es juvenis (0,93 g ?
0,29) e pr?-adultos (10,05 g ? 1,18) foram coletados da Esta??o de Aq?icultura da Universidade Federal Rural do Semi-?rido UFERSA, e mantidos por 10 dias em tanques de 500 L, com alimenta??o, aera??o constante, temperatura,
pH e salinidade est?veis. Tr?s grupos granulom?tricos foram pr?-estabelecidos como substratos experimentais: C= silte + argila; B = areia muito fina + areia fina; A= areia m?dia + areia grossa + areia muito grossa + cascalho. Seis diferentes combina??es de substratos foram testadas: A, B, C, A+B, A+C, B+C. Utilizou-se tanques cil?ndricos (40L), com fundo preenchido por 6 bandejas. A cada bateria, trocou-se os sedimentos e ?gua, evitando a influ?ncia de ferom?nios e caracter?sticas alteradas do sedimento. Inicialmente pesou-se os camar?es individualmente e os organismos pr?-adultos separados por sexo, com base em caracteres externos: presen?a do petasma nos machos e t?lico nas f?meas. Colocou-se 1 camar?o/tanque, tendo livre e imediato acesso aos diferentes tipos de sedimentos. Para observa??o na fase escura, utilizou-se o aux?lio de luz vermelha. O m?todo de observa??o foi o Animal Focal Instant?neo, com registro a cada 2 minutos, em janelas de 20 minutos, em 8 hor?rios ao longo do dia: 19:30 h; 20:30 h; 00:30 h; 1:30 h; 05:30 h; 06:30 h;13:30 h; 14:30 h, totalizando 88 registros em 24 horas. Utilizou-se 54 camar?es de L. vannamei (18 machos, 18 f?meas e 18 juvenis). Observou-se: a) freq??ncia de visita; b) comportamento de enterramento e desenterrado; c)
Atividade natat?ria. Diante dos dados obtidos, observou-se maior freq??ncia de visita??o do L. vannamei, tanto jovem quanto pr?-adulto, no sedimento B. Este animal apresenta atividade c?clica, permanecendo enterrado durante o dia na
maior parte dos hor?rios observados e exercendo nata??o durante a noite. N?o houve diferen?a significativa no comportamento de enterramento das f?meas. O comportamento de nata??o foi mais freq?ente na fase escura quando comparada ? fase clara, principalmente nos hor?rios de 00:30 e 01:30 horas
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