Preparation of acetate peels of valves from the ocean quahog, Arctica islandica, for age determinations

Techniques are described for preparing acetate peels of sectioned valves of ocean quahogs, Arctica islandica, for age determinations. The respective sequence of preparation begins by sectioning left valves oriented to include a single hinge tooth, bleaching to remove the heavy periostracum, embedding the valves in an epoxy resin, grinding and polishing the embedments to a high luster, etching the exposed cut valve surfaces, and applying sheet acetate with acetone. Annuli are clearly defined relative to growth increments in the peel preparations for all sizes and ages of ocean quahogs. (PDF file contains12 pages.)

Influence of number of valves on catch composition of a fishing pot trap (Lege) in River Rima, north western Nigeria

Three types of prototype (Lege) traps with different numbers of entrance valves were evaluated in River Rima, north western Nigeria. The traps contained 4,6 and 8 valves, tagged 4-V, 6-V and 8-V respectively. The experiment was carried out in a randomized complete block design with one factor each replicated three times. Data collected on fish diversity, number biomass and sizes were subjected to descriptive statistics and analysis of variance. The results of the catch composition showed close diversity index of 0.86 for 6-V, 0.80 for 8-V and 0.60 for 4-V Lege traps. However, the number (41%) and biomass 48%) of fish caught in the 6-V Lege trap were significantly (P0.05) higher than those caught in the other traps. There was no definite trend in the sizes (length and girth) of fish caught in the traps. On the basis of species diversity, and the number and biomass of fish caught, the 6-V Lege showed preference for adoption than the other two traps. However, further studies are recommended on the appropriate mesh size net for the trap in line with the provisions of fisheries edicts

Influence of number of valves on catch composition of a fishing pot trap (Lege) in River Rima, north western Nigeria

Three types of prototype (Lege) traps with different numbers of entrance valves were evaluated in River Rima, north western Nigeria. The traps contained 4,6 and 8 valves, tagged 4-V, 6-V and 8-V respectively. The experiment was carried out in a randomized complete block design with one factor each replicated three times. Data collected on fish diversity, number, biomass and sizes were subjected to descriptive statistics and analysis of variance. The results of the catch composition showed close diversity index of 0.86 for 6-V, 0.80 for 8-V and 0.60 for 4-V Lege traps. However, the number (41%) and biomass (48%) of fish caught in the 6-V Lege trap were significantly (P<0.05) higher than those caught in the other traps. There was no definite trend in the sizes (length and girth) of fish caught in the traps. On the basis of species diversity, and the number and biomass of fish caught, the 6-V Lege showed preference for adoption than the other two traps. However, further studies are recommended on the appropriate mesh size net for the trap in line with the provisions of fisheries edicts

Estimating the underwater shape of tuna longlines with micro-bathythermographs

An estimation method for the three-dimensional underwater shape of tuna longlines is developed, using measurements of depth obtained from micro-bathythermographs (BTs) attached to the main line at equally spaced intervals. The shape of the main line is approximated by a model which consists of a chain of unit length lines (folding-rule model), where the junction points are placed at the observed depths. Among the infinite number of possible shapes, the most likely shape is considered to be the smoothest one that can be obtained with a numerical optimization algorithm. To validate the method, a series of experimental longline operations were conducted in the equatorial region of the eastern Pacific Ocean, using 13 or 14 micro-BTs per basket of main line. Concurrent observations of oceanographic conditions (currents and temperature structure) were obtained. The shape of the main line can be calculated at arbitrary times during operations. Shapes were consistent with the current structure. On the equator, the line was elevated significantly by the Equatorial Undercurrent. It is shown that the shape of main line depends primarily upon the vertical shear and direction of the current relative to the gear. Time sequences of calculated shapes reveals that observed periodic (1-2 hours) oscillations in depth of the gear was caused by swinging movements of the main line. The shortening rate of the main line is an important parameter for formulating the shape of the longline, and its precise measurement is desirable.

Effect of different media on the determination of the number of micro organisms in frozen prawns (shrimp)

The Indian standards Institution have recently laid down specifications for the grading of frozen shrimp of which the bacterial examination of the product forms a significant part. Work carried out in this regard in our laboratories have shown that various improvements could be made in the composition of the medium to obtain a more true picture of the total bacterial count. Changes in the medium for total bacterial count have, therefore, been suggested and the reasons for the same discussed.

Growth and reproductive performance of locally isolated brackish water rotifer (Brachionus plicatilis) feeding different micro algae

Population growth and reproductive capacity of brackishwater rotifer, Brachionus plicatilis, were evaluated, for a period of 8 days in a temperature controlled ( =25°C) microalgallaborarory, under three different algal feeding regimens. The algal species that were tested are: (i) Chlorella sp. (T1), Tetraselmis chui (T2), Nannochloropsis oculata (T 3). The feeding density of each algal species was maintained similar as of 4.5xW6 ceHs mi. The rotifer fed on T. chui showed the highest (p<0.05) population growth (131.5 ind./ml), compared to that fed on Chlorella sp (45.67 ind./ml) and N oculata (43.44 ind./ml). The abundance of egg bearing rotifers was also higher (35.77%) with T. chuithan with Chlorella sp (27.76%) and N oculara (24.60%). The results of the present study indicate that T. chui could be the most suitable algal food for the stock culture of locally isolated rotifer B. plicatilis.

Estimation of micro-flora associated with different stages of Macrobrachium rosenbergii (de Man)

The bacterial flora occurring in muscle, haemolymph, hepatopancreas and gill of brood, juveniles, water, eggs, larvae and rearing water were estimated by selective plate count technique for Entrobacteriaceae, Streptococaceae and Vibrionaceae members. The total viable bacterial count was estimated by total plate count technique on nutrient agar. The total viable counts of bacteria were lowest in water from 6.10x10² CFU/mL) and highest in egg (6.06x10super(8) CFU/g). In brood the total counts were varying from 1.62x10² CFU/g in muscle to 2.20x10super(5) CFU/g in gills. In juveniles, the total plate counts were varying from 2.8x10super(4) CFU/g in muscles to 3.67x10 super(8) CFU/g in hepatopancreas. Selective plate counts show that Enterobacteriaceae members dominate in egg and gills of brood and hepatopancreas of juveniles. Vibrios were found to be dominant in water and larvae of rearing tank. Haemolymph of brood was sterile and did not contain any bacteria while muscle of juvenile was having very low count of total viable bacteria.

A programme to carry out analysis of variance: two-way classification on Micro 2200

A brief description is given of a program to carry out analysis of variance two-way classification on MICRO 2200, for use in fishery data processing.