Length-weight relationship and relative condition factor in Daysciaena albida (Cuv.) and Gerres filamentosus (Cuv.)

The length-weight relationship of Daysciaena albida and Gerres filamentosus were calculated separately for indeterminants, mature males and mature females. The logarithmic regression equation obtained for D. albida - males: log w = -1.5055 + 2.8618 log l; females: log w = -0.9260 + 2.4089 log l; indeterminants: log w = -l.7188 + 3.0616 log l. The regression co-efficients between males and females, males and in determinants and female and in determinants showed significant differences. In G. filamentosus the relationship can be expressed as males: log w = -1.3224 + 2.8740 log 1; females: log w = -1.2874 + 2.8381 log l; indeterminants: log w = -0.8167 + 2.2558 log l. The difference in regression co-efficients between male and female are insignificant at 5% level whereas significant differences were observed between males and indeterminants and females and indeterminants. The relative condition factor (Kn) was calculated for the above two species. In D. albida the reasons for the fluctuations of Kn values can be attributed to both spawning cycle as well as feeding intensity whereas in G. filamentosus it synchronies mainly with spawning cycle.

Length-weight relationship of Tilapia mossambicus of Idukki Reservoir

The results of ten months study (September 1983 to July 1984) of the length-weight relationship of males and females of Tilapia mossambicus of the reservoir waters of Idukki Hydel Project show deviation from the cubic relationship of these two parameters. This is due to the retarded growth pattern of this exotic species in this oligotrophic habitat.

Changes in length and weight of milkfish fry preserved in formalin

Fry shrank immediately after they were preserved in formalin, but from the second week onwards shrinkage was almost nil. Fry in freshwater formalin solutions shrunk less than those in seawater formalin solutions. It is recommended that milkfish Chanos) fry be preserved in formalin solutions for 1 wk prior to length measurement and at least for 3 wks before determining body weight.

Observations on the artificial fertilization of eggs and larval rearing of the grey mullet, Mugil cephalus L.

The results are presented of attempts to artificially fertilize Mugil cephalus eggs in the Philippines. Embryonic development is outlined and rearing of the larvae described. Mass mortality occurred during week 3 of rearing.

Notes on the pigmentation pattern in the larval developmental stages of laboratory-reared milkfish

Milkfish fry were artificially bred and reared in the laboratory and the pigmentation pattern of the different developmental stages of the larvae are described in detail, with illustrations.

Experiment on larval rearing of Penaeus monodon fed with cultured diatom Chaetoceros calcitran and fermented vegetable trash

A brief account is given of experiments undertaken rearing Penaeus monodon larvae fed on diatom (Chaetoceros calcitran) and fermented vegetable trash, which included fruits and their peels, vegetables and rice. The possible use of high protein content trash materials as a feed substitute is examined briefly.

Length-weight relationship of two palaemonid prawns, Macrobrachium idella and M. scabriculum: a comparative study

Length-weight relationships of two commercially important freshwater prawns, Macrobrachium idella and M. scabriculum, have been worked out separately for the two sexes of the two species. 't' test showed that growth departs significantly from the isometric growth in the case of both sexes of M. idella and in the female of M. scabriculum. Therefore, the cubic formula W = CL^3 may be applied only in the case of males of M. scabriculum. In all the other cases W = CL^n may be followed.

Solid loss and weight gain in prawns during storage in ice

Loss of solids from and gain in weight of meat of whole prawn and prawn meat stored in ice has been studied to explain the mechanism of solid loss. Two stages are identified in this phenomenon. In the first stage water is absorbed without loss of solids resulting in a maximum increase in weight. In the second stage both solids and water are lost resulting in gradual decrease in weight from the maximum reached but not reaching the original weight. It is inferred that whole prawns stored in ice up to two days give the maximum peeled yield without loss of nutrients and at the same time making the peeling process easier.

Viability of frozen algae used as food for larval penaeids

Freezing with added chemicals as flocculants and protectants was assessed as a means of preserving stock cultures of 4 algal species used for larval penaeid food Chaetoceros calcitrans, Skeletonema costatum, Tetraselmis chuii and Isochrysis galbana . The maximum storage effectability of the preservation techniques for each species was also determined.

Growth phases of cultured algae used as larval food

A study was undertaken to determine the onset and duration of the growth phases of cultured algae commonly used as larval food (Skeletonema costatum, Chaetoceros calcitrans, Tetraselmis chuii, Chlorella vulgaris, Isochrysis galbana) so as to predict the time of harvest at the desired stage to suit various needs and purposes.

Larval and postlarval development of the window-pane shell, Placuna placenta L. (Bivalvia: Placunidae)

Stages of development of P. placenta from the straight-hinge veliger to the adult are described. Mature larvae metamorphose at lengths from 220-230 m. Larvae probably attach byssally to the water surface at metamorphosis and remain in the plankton for some time before finally settling on the mud bottom.

Bacteria from seawater used in Penaeus monodon larval cultures

Bacteria in the seawater used in P. monodon hatchery operations were isolated on Bachmann's agar. The total plate counts in 25 isolations ranged from 1.0 - 5.0 x 10² to 5.1 -10.0 x 10⁵ cells per ml. Out of 124 isolates, 98 (79 percent) were Gram-positive and 26 (21 percent) were Gram-negative. Micrococcus and Staphylococcus were dominant in the former group, while Acinetobacter, Moraxella, Flavobacterium and Alcaligenes were most numerous in the latter. Twenty-nine of the Gram-positive isolates closely resembled Peptostreptococcus, Planococcus, and Pediococcus.

Viability of frozen algae used as food for larval penaeids

Freezing with added chemicals as flocculants and protectants was assessed as a means of preserving stock cultures of 4 algal species used for larval penaeid food Chaetoceros calcitrans, Skeletonema costatum, Tetraselmis chuii and Isochrysis galbana. The maximum storage effectability of the preservation techniques for each species was also determined.

Length-weight relationship in Nandus nandus (Hamilton) (Perciformes-Teleostei)

Length-weight relationship of the freshwater fish of Pamba River, Nandus nandus (Ham) has been worked out. The results showed that the slope values and elevations were not significant and hence a combined regression equation has been calculated for both the sexes (Log W=2.4130 Log L -0.3306). The’t’ test analyses were conducted and found that the growth departs significantly from the isometric growth. Thus the formula W=aL super(n) has to be applied in calculating the length-weight relationship of this species.

Use of eye lens diameter and weight as an age indicator in the carangid fish, Decapterus russelli (Pisces: Carangidae) from Gulf of Oman: preliminary observation

Specimens of Decapterus russelli have been collected from Lema, north of the Gulf of Oman. The ocular lens diameter and weight were tested as an additional age indicator to those already in use. The results showed that this technique could be adopted for determining the age of the species Decapterus russelli when the specimens are in the second year of age in case of eye lens diameter. On the other hand, eye lens weight failed to separate between the four age groups observed. The method is especially useful for age determination when otolith or scale ring are not visible or when false rings give erroneous reading.