Claudia Carmona-Osalde

Gonadal development, spawning, growth and survival of the crayfish Procambarus llamasi at three different water temperatures

A study was done of the effect of three water temperatures (16, 21 and 26 °C) on the growth, survival, gonad development and spawning rates of Procambarus llamasi during a 90-day trial. Juveniles (<40 mm total length) were stocked at 76 org/m2 density, and at a 1:1 M/F ratio. Growth improved in all treatments with increasing temperature, showing significant differences between sexes. Males grew more than females and achieved larger sizes with statistical differences (p<0.05) between treatments. Survival rate exhibited a negative relationship to temperature, with significant differences (p<0.05) between the 16 °C treatment and the others, but not between the 21 and 26 °C. Survival rate decreased from 90% at 16 °C to 42% at 26 °C. Ovary development increased as temperature increased. The gonadosomatic and maturation indexes were significantly different (p<0.05) between the 16 °C treatment and the others, but not between the 21 and 26 °C treatments. Spawning rate exhibited no relationship to temperature, with optimum results (22%) at 21 °C.

Estimation of the protein requirement for bullfrog (Rana catesbeiana) tadpoles, and its effect on metamorphosis ratio

Abstract Six protein levels (30%, 35%, 40%, 45%, 50% and 55%) were tested in isocaloric diets for bullfrog tadpoles, to evaluate its effects on weight gain and metamorphosis establishing the optimum dietary protein level for this organism. It was found that weight gain data were not adequate for calculating protein level. Cumulative frequency of metamorphosis showed a direct relationship with dietary protein, this being suitable for use as a parameter to evaluate the protein requirement for tadpoles. Using this method, an optimum level of 44.61% crude protein was determined.

The influence of the absence of light on the onset of first maturity and egg laying in the crayfish Procambarus (Austrocambarus) llamasi (Villalobos, 1955)

Abstract Procambarus llamasi is a crayfish species endemic to southeastern Mexico. Of all the portions of a species lifecycle to be understood, reproduction is the most vital. In order to better understand the effect of external factors on the reproductive development of P. llamasi, an experiment was done testing the influence of complete darkness (CD) and a natural light cycle (NL) on first maturity and egg laying. During the 90-day experiment, three tanks were covered with dark plastic to prevent light from entering (complete darkness, CD), and another three were covered with transparent plastic to allow a natural light cycle (14L:12D, NL). Sexually immature juveniles were placed in the tanks and their growth and sexual maturation monitored. At the end of the experiment, the general spawning mean was 24% for the CD treatment and 15% for the NL treatment. The maturation index was 4.04 for the CD and 3.88 for the NL, and the gonadosomatic index was 3.90 for the CD and 4.20 for the NL. In contrast to many other crayfish species, it is determined that complete darkness does not affect growth, survival or reproduction in P. llamasi. Reproductive development in this species may respond to other external factors such as hydrological cycles.

Growth and production of bullfrog Rana catesbeiana shaw, 1802, at three stocking densities in a vertical intensive culture system

Abstract Newly metamorphosed froglets of Rana catesbeiana were experimentally cultured in a three-dimensional (vertical) system at 50, 100 and 200 animals m−2. The culture system consisted of nine sections (three per treatment) in a vertical array where frogs were provided with food and water in replaceable troughts. After 8 weeks, frogs stocked at 200 m−2 developed a severe bacterial infection, leading to high mortality and the cancellation of this treatment. There were no significant differences (P > 0·05) among frogs stocked at 50 and 100 m−2 after 175 days, reaching 118 g and 105 g mean final weight, respectively. Survival was inversely related to stocking density, amounting to 72% and 65% for 50 m−2 and 100 m−2, respectively. Yields were 4·33 kg m−2 and 6·87 kg m−2 for the former and the latter densities, respectively, thus demonstrating the high production potential of vertical frog rearing systems. These results indicate lower yields than reported in studies using two-dimensional systems, but per unit area, they gave higher yields.

Total and partial substitution of dietary fish oil with palm oil to juvenile crayfish, Procambarus llamasi.

A 12-week feeding study was carried out to establish the effect of partial or total substitution of fish oil by plant oil in experimental fed diets in crayfish juveniles (Procambarus llamasi). Three isonitrogenous (30% crude protein) and isoenergetic (15.1 kJ/g) practical diets were formulated with 100% fish oil (FO), 100% plant oil (PO), and 50% FO-50% PO. The crayfish were raised on plastic tanks without water exchange, constant aeration, PVC shelters, with an average water temperature of 26 ± 1°C. Uneaten food and fecal residues were siphoned out from the tank bottom each morning. Crayfish total body weight (BW) and total length (TL) was measured every two weeks. Results showed that the use of plant oil did not significantly modified (p>0.05) growth performance, survival or maturity of experimental organisms. All diets were offered to apparent satiation twice a day. Fed was consumed showing good results in all performance growth parameters and maturity index. In conclusion the present study clearly supported the possibility of total or partial substitution of fish oil by plant oil for crayfish. Despite the absence of fish oil as attractant in the diet with 100% PO, its acceptance was as good as the one containing it. P. llamasi demonstrated the feasibility of using a vegetable oil as lipidic energy source, which allows lowering costs in the use of fish oil about 66%.