Fishery, population characteristics and stock assessment of cuttlefishes, Sepia aculeata and Sepia pharaonis at Kakinada along the east coast of India

Cuttlefishes were exploited exclusively by trawls along the coast. Growth, recruitment, mortality and exploitation rates of Sepia aculeata and Sepia pharaonis were studied. Fishery of the former was supported mainly by zero year and the latter by zero and one + age groups. Both attain sexual maturity during the first year itself and spawn during August-March with peak during November-December. Natural mortality of S.aculeata was 2.22, fishing mortality 2.34 and total mortality 4.56. It was 1.69, 1.97 and 3.66 respectively for S.pharaonis. Exploitation rate was 0.52 and Emax 0.72 for S.aculeata and it was 0.54 and 0.76 respectively for S.pharaonis. Their mortality and exploitation rates indicated that stock remains under-exploited and have considerable scope for improving the production. However, both stock and catch exhibited wide annual fluctuation with declining trend during the period. These necessitated immediate attention including measures to minimise juvenile exploitation for improving stock and fishery.

Studies on the age and growth of Labeo calbasu (Hamilton) with an exploitation pattern from the Ganga River system, Uttar Pradesh (India)

Samples were collected to study the age and growth of Labeo calbasu (Hamilton) from the river Ghaghra (Guptarghat centre, Faizabad). The scales of L. calbasu have been used for age and growth studies in present paper. Study of the marginal rings on the scales of L. calbasu indicates their annual nature. The fish attained growth in 1st 18.7 cm, 2nd 27.8 cm, 3rd 35.7 cm, 4th 41.8 cm, 5th 46.9 cm, 6th 54.9 cm and 7th 57.4 cm years of the life. The growth rate was observed 18.7, 9.1, 7.9, 6.7, 5.1, 8.0 and 2.5 cm for 1st to 7th age classes respectively. The age groups 1+ to 4+ constituted 91.17% of the total exploited population and 8.83% of remaining age groups (5+ to 7+). The maximum exploited population was observed in 2+ age group with 33.68%. Overall exploitation pattern was systematic and a good indicator for heavy recruitment.

Rational exploitation of Catla catla (Ham) from Hirakud reservoir: a preliminary account

Frame nets and simple gill nets of identical mesh size were experimented to determine their comparative efficiency for exploiting economic size group of Catla catla. The results indicated that frame nets of 90 mm mesh bar as the most effective.

Histology and hormonal effect of Ghrelin on ovary of Benni (Barbus sharpeyi) in order to study sexual maturity, zygote and larval generation

Benni (Barbus sharpeyi) is valuable fish that Khuzastan fisheries office propagated it artificially in Susangerd Fish Propagation Center every year. Pituitary gland is used for this aim but female fish lost their fertilization power after 2-3 years, so in present research, new hormone, that is called Ghrelin. The aims of this research are histology, hormonal, zygote and larval generation studies and comparing the results with each other. Ghrelin is a multifunctional peptidyl hormone which increases GTH-II in fish, amphibian, and birds and mammalian so its effect on Benni sexual maturation was studied. Human Ghrelin (hGRL) was obtained from ANASPEC, Canada, with 28 amino acids. In the present study, three levels of ghrelin including 0 (sham treatments), 0.10 (treatment 1) and 0.15 μg/g (treatment 2) body wt and one level of pituitary gland 4000 μg/g (pituitary treatment) with two replications were used. 56 specimens were injected intraperitonealy and their ghrelin level was evaluated immediately after injection and after 24 h. Control fish(n=16) were just injected by physiological saline. For hormonal studies sham and experimental fish(n=40) were anesthetized with MS-222 at a concentration of 250 mg l-1, and blood samples were collected and kept at 4ْC, then spun to collect serum. Serum samples were stores at -20ْC until the RIA for CTH-II. For histology studies immediately after injection a piece of ovary was collected from control fish (Sham zero) after being anesthetized. The sampled ovaries were fixed in Buin solution and embedded in paraffin, and stained to Sections of 5–6 μm using haematoxylin and eosin. The ovarian samples were performed with a compound microscope. Histology and micrometry studies had done. The mature oocytes had given from mature fish, then weighted and the working fecundity were counted. The mature oocytes fertilized, the eggs were incubated and the percentage of fertilization was calculated. After 72h the eggs hatched and the percentage of hatch was counted. The percentage of hindrance was calculated after 6 days. Hormonal results indicate that ghrelin and pituitary increase significantly the GTH-II level in comparison to sham. Macroscopic observations (before taking ovary) showed that ovaries with green colored have couple oval structure located in the abdominal cavity. Microscopic studies of dissected ovaries indicated simultaneous growth of 127 oocytes with 6 stages. The type of the ovary is asynchronous. The results indicated that both of the ghrelin treatment increased the percentage of mature follicles followed by decrease of immature follicles. There were significant differences (P<0.05) between the number of mature and immature follicles. Average diameter of follicle in both of the ghrelin treatment was significantly (P<0.05) declined in the stages of the vitellogenesis when the result compared to the other treatment. Just treatment 1 and pituitary treatment can give mature oocytes. The fecundity of pituitary treatment significantly increase in comparision to ghrelin treatment (P<0.05). In food-restricted fish where endogenous ghrelin levels are known to be increased, a chronic administration of ghrelin induces overt negative effect in releasing mature oocytes. The percentage of fertilization was significantly increase (P<0.05) in ghrelin t. in comparison to pituitary t. and the percentage of hatch was significantly increase (P<0.05) in pituitary t. in comparison to ghrelin t. There was no significant difference (P>0.05) in terms of percentage of hindrance between treatments. In conclusion, the present study demonstrated that ghrelin has positive effect on the level of GTH-II, oocyte maturation, ovarian vitellogenesis and the number of mature follicles of Barbus sharpeyi ovary. Increasing of the mature follicles number reduces their average diameter, indicating stimulating effect of ghrelin in sexual maturation of Barbus sharpeyi.The ghrelin and pituitary treatment have equal chance in the post-stage of spawning.

Study on biological characteristics, sexual maturation and reproduction of Liza abu in the water of Khozestan Province

As the most of the fish resources are known and exploited, protecting their generation is of the greatest importance. Aquaculture is one of the efficient procedures in protecting and reviving fish resources and knowing about the reproductive cycle and gonads development has an important role in approaching this aim. Liza abu belongs to the family Mugilidae that according to its resistance to the environmental condition and its fast growth , can be introduced as a fish with economical value. As there is no scientific data on the reproductive biology of this species , study on the reproductive biology and gonad development is considered as the aim of this research . For this purpose , 360 samples of this species were investigated during the period from February 2007 to January 2008 in Khozestan Province . After studing morphological and histological characteristics of gonad specimen , they were prepared through histological method. Samples were prepared through usual histological method and studied under light microscope. According to the results, the maturity stages of male and female Liza abu were separated to six different successive stages. In ovaries , these stages were as follow : In stage І, the oocytes were small , this stage was observed from July to October . In stage ІІ, considerable growth was observed in the oocytes . This stage was observed from October to January . In stage III, due to vitellogenesis, the maximum growth was observed and three layers of theca, granullosa and follicle cells were visible. This stage was observed during January and February . In stage IV, migration of germinal vesicle was observed and due to hydration of the oocytes , their diameter was increased. The ovaries were yellowish and in maximum size and ovules could be easily observed with naked-eye . This stage was observed in February and March . In stage V, spawning occured. This stage was observed in April . In stage VI, ovaries consisted of immature and atretic oocytes and also empty follicles. This stage was observed in May and June. In testes , these stages were as follow : In stage I , the testes were small in size and contained the spermatogonia which were the only cellular components.This stage was observed in August and September . In stage II (maturing virgin ) , the spermatogonia and the primary spermatocytes were visible. This stage was observed in October . In stage III (developing), intensive spermatogenesis was occured and the primary and the secondary spermatocytes were the most visible cells during this stage .This stage was observed from November to January. In stage IV(developed), cells of all stages of spermatogenesis could be seen but the secondary spermatocytes and spermatids were in large number. This stage was observed from January to March. In stage V , the testes were filled with sperms. This stage was observed in March and April .In stage VI, residual spermatozoa and the spermatogonia were visible in the testes. This stage was observed from May to August. According to cyclic changes in GSI, sexual maturation in breeding begins in January and spawning occurs in April. The ova diameter ranged from 30.75 μ in stage I to 472.19 μ in stage IV. In this study , the sex ratio was 1:2.7, and male and female percentage were 27.02% and 72.98% respectively. This means that females predominate males. In this study absolute fecundity was calculated and changing between 30805.44 to 431247.3 was observed and absolute fecundity was calculated 111275.3 in average.

The survey of sexual maturity in Mugil cephalus so measuring sex hormones and histologic studies

In this study the process of female gray mullet brooders was carried out by using histological study and masurment of sex steroids. Results of histological studies showed that oocyte of gray mullet brooders in Gomishan Rearing Center conditions of develop to the end of yolk globule stage. The results were observed with oocyte in chromatin nucleolar stage (first stage) with means of diameter of 20 p m, in August, perinucleolar stage (second stage) in September with mean diameter of 87 p m, yolk vesicle stage (third stage) in October with mean diameter 200 p m and yolk granules stage (forth stage) from October to November with average diameter of 180 — 650 p m. For the reason of stopping oocyte develop at the end of fourth stage, hormonal induction to final oocyte maturation and ovulation was used. For this purpose, carp pituitary , HCG and LRH-A2 with different combinations were used in two stages, second injection was used 24 hours after first injection. 15 females brooders were divided in 5 groups, different hormonal combinations were injected to four groups and to fifth group as control, only saline, was injected. The process of female brooder rippening in hormonal induction was studied via masurment of sex steroids including 17 a - hydroxy progestrone, estradio1-17)6 and testosterone. Blood samples were collected from caudal vein during first injection, 24, 30 and 48 hours after the first injection. At the same time, for distinguishing histological changes the sample has been attained from the gonads Sex stroid fluctuation patterns in different brooder groups that injected hormon were similar, however hormonal composition had similar effects. All brooder that their oocyte in the beginning of hormonal injection were At the end of fourth stage with oocyte diameter average of 600 p m received to final maturation and ovulation. The brooder that its oocytes were At the begining or mid-fourth stage did not show ovulation but hormonal induction caused oocyte develop at the beginning of fifth stage. Study of 17-hydroxy progestrone fluctuation showed that the maximum level of this steroid (0.347 ng/ml) measured 30 hours after the first injection and was significantly higher (p< 0.05) than those of control group. So, 17-hydroxy progestrone is probably precursor of maturation inducing steroid (MIS). However the maximum level of that observed was coincident with germinal vesicle breakdown, oil droplets coalescence and dissolution of yolk granuls The maximum levels of esteradiol— 17/0 and testosterone (3.778 and 16.801ng/ml,respectively) in spawned brooders,were observed 24 hours after the first injection. levels of those steroids were significantly higher (p<0.05) than control group. Maximum level of sex steroids in the brooders that did not spawn to the end of treatment was observed with more delay than those in spawned brooders. Therefor maximum level of 17a-hydroxy progestrone (0.264 ng/ml) in those brooders observed in fourth sampling time and the maximum levels of estradio1-17a and testosterone (2.944 and 18.993 ng/ml, respectivly)observed in third sampling time that was significantly higher (p<0.05) than those of control group. For the study of stress effect on brooders during the hormonal induction, level of cortisol was measured in every sampling time. level of cortisol had high fluctuation that showed handling level and stress effect on brooders. However maximum level of cortisol in majority of brooders was dominant in third sampling time that was coincident with final maturation.

Survey of biosystematic and sexual reproductive physiology in Holothuroidea on Hormozgan Province

Sea cucumbers belong to phylum Echinodermata, order Holothuroidea are an abundant and diverse group of Invertebrates, with over 1400 species occuring from the intertidal to the deepest oceanic trenches. Sea cucumbers are important components of the food chain in temperate and coral reef ecosystems and they play an important role as deposite feeders and suspension feeders. Rapid decline in populations may have serious consequences for the survival of other species that are part of the same complex food web,as the eggs, larve and juveniles constitute an important food source for the other marine species including crustaceans, fish and mollusks. In addition sea cucumbers are often called the earthworms of the sea, because they are responsible for the extensive shifting and mixing of the substrate, and recycling of detrital matter. Sea cucumbers consume and grind sediment and organic material into finer particles , turning over the top layers of sediment in lagoons , reefs and other habitats and allowing the penetration of oxygen. While the taxonomy of the holothurian families is generally well known , the distinction of similar species is difficult. There are relatively few holothurian taxonomist.Most sea cucumber species can be identified by Holothurin taxonomists by using the calcareous skeletal ossicles found in the body wall. In this study , at first a sea cucumber from Kish island in Persian gulf has recognized. Individuals collected from west and east extend far away into north and south of coral reefs by diving. I have checked them morphologically and anatomically.Then with key to the orders of the Holothuroidea, They belong to the Aspidochirotida with key to the families of Aspidochirotida, they were in Stichopodidae families and with key to the genus of Stchopodidae, they were Stichopus. Then ossicles were extracted at National Museum of Natural History, by Dr David Pawson. The ossicles were measured on a transect across a slide prepared from the mid-dorsal region of each specimen.The one we have in the shallow waters of Kish island, is Stichopus hermanni, a massive holothurian, body broad, considerably flattened ventraly ,the dorsal side slightly arched and the lateral sides almost vertical; body wall fairy thick and soft ; mouth subterminal; anus central; tentacles usually 20 in number of length and leaf shaped. Numerous ossicles consisting of table with large discs having usually 7 to 15 peripheral holes, but often irregular or incomplete and spire of moderate height ending in a group of spinelets, rosettes of variable development, and c-shaped rods. Color (exept papillae)partly remained after preservation in alcohol which is found at the depth of 4 to 8 meters, on coral reef. Furthermore, the sexual reproductive cycle was described using standard methods. Gonads were removed and transferred to Bouin's fixative for four weeks and then processed according to standard embedding technique. To prevent the loss of tubule contents during embedding, the tubule sections, were cut well beyond the segment selected for sectioning. For each individual, six sections, each section with 5µm diameter by microtome were cut from tubules. These sections were first placed on gelatin coated slides (the gelatin was heated to 42°c) and then transferred to the oven at 37°c for one hour. This technique usually prevents the fragil tubules from breaking and the loss of gametes. The slides were stained with Eosin and Hematoxylin, and good resolution of the various cell types achieved.A second series of slides was stained with the Periodic Acid Schiff(PAS) to identify polysaccharides(glycogen). Monthly sampling was occurred.The sexual reproductive cycle was defined through the combined use of these criteria: Monthly percentages of the gonad stages for each sex, the monthly gonad index (GI) , given as the ratio of the wet gonad weight (G) to the dray weight (DW)and the monthly percentage of individuals that undetermined sex. The gonad consists of two tufts of tubules on which saccules develop. Gonadal development was classified into five stages: post spawning, recovery, growth, advanced growth, and mature stage that were adapted from the earlier studies of holothurians. Histological preparations showed that the sex of larger individuals could be identified by the presence of oogonia and young oocytes in females, and spermatogonic stages in males.The mean diameter of the tubules and gonadal mass follow annual cycles, increasing from late winter through spring, and dropping abruptly after spawning in the summer. Gametogenesis is generally a prolongate process and begins in March. By summer the ovarian tubules contain oocytes with diameter of 120-240 pm and the testicular tubules contain an abundance of spermatozoa (diameter 5-6 gm ).Following spawning the predominant activity within the spent tubules is phagocytosis of the residual gamets.The active phase of gametogenesis (March to July), coincides with an increasing photoperiod regim, and an accelerated gametogenesis occurs in July when temperature is high. Throughout the year, the gonad of Stichopus hermanni is larger in males than in females, and this is due to the number of tubules in the testis rather than to tubules length or diameter.

The fisheries and fish stocks of Lake George: their productivity, exploitation, management and conservation

The study was confined to the fisheries of Lake George. The fishery of Lake George has been exploited under controlled exploitation but the permitted number of boats was fixed in the 1950s before the human population increased to the current level. Many more people were involved in fishing and it was feared that the fish stocks might not support the human population. The assignment involved preparation of a research proposal, collection of field data and production of a report in a period of eight months.

Fishery resources: their exploitation, management and conservation in Africa

The beginning of the 20th century saw the discovery of Africa's vast natural resources. Not only did explorers "discover" lakes, rivers, forests and mountains but scientists and naturalists also "discovered what at that time were called new species of plants, fish and other animals. Thus scientific names were tagged to various species using the famed binomial nomenclature and immortalising the names of some of the people who first described those species. Africa of course abounds with thousands of different floral and faunal varieties and the early colonial scientists found the African environment lucrative fron the point of discovery of new species. This paper therefore attempts to descrihe the role science could only in the development and exploitation of one of Africa's renewable resources namely fisheries. This paper has attempted to expose the value of fish in human nutrition, provision of employment and uplifting of social and economic standards. The fishery resources of Africa are extensive and in the main not fully exploited. These resources like other natural resources are exhaustible although renewable. Efforts to exploit these resources must be encouraged but scientific planning and management of the resource is called for.

Fish exploitation and changes in the fish community of Lake George, Uganda

Unlike Lake Victoria, the fisheries of Lake George have undergone gradual changes in the size and proportion of the major commercial fish species, the Nile tilapia (Oreochromis niloticus: cichlidae) in the last 40 years (1950-1989). The size decreased from an average weight of 900g in 1950 to 430g in 1989 while percentage contribution in commercial catches during the same period declined from 92% to 36%. The over all annual commercial catches though showed a steady increase from the period 1950 when the fishery was opened to intensive and controlled exploitation, consistently high catches were observed in the 1960s and 1970s followed by a general decline in the early 1980s to amore or less stable fishery in the late 1980s. These changes are attributed to increased fishing pressure especially on the nil tilapia and to increased use of smaller gill net mesh sizes lower than the recommended 127mm mesh. The changes in gill net mesh have brought O. leucostictus, acichlid, into commercial catches confirming that the 88.9mm mesh size nets are used by the commercial fishermen to harvest smaller fish species. The commercial catches are presently dominated by the piscivorous fishes,(over 60%) whose contribution was less than 10% during initial exploitation of the virgin fishery in 1950.The piscivorous fish are mainly caught using hooks and lines. The entire fishery is believed to be exploited close to the maximum. The above trends serve to show the impact of exploitation on fish species diversity. Quantitive and qualitative changes of the major fish species on lake George are due to exploitation pressure unlike Lake Victoria where it is a combination of both exploitations and impact of fish introductions. There has been no fish introduction in Lake George.

A decline in fish catches and the size of Oreochromis niloticus in Lake Wamala (Uganda) following human exploitation

The fishery of Lake Wamala has declined since the lake was stocked in 1956 and opened to fishing during the 1960s. Surveys were conducted on the lake during 1975/78 and 1988/92 to investigate the causes of declining fish catches. The lake produced an average of 4000 - 6000 tonnes of fish annually from 1960s through 1970s. Total fish catches decreased from a maximum of 7100 tonnes in 1967 to less than 500 tonnes by 1990s. Catch rates decreased from about 8 kg in the 1960s to less than 1 kg per net per night by 1975. During the 1970s the catch was dominated by Oreochromis niloticus (67%) followed by Clarias gariepinus (17%), and Protopterus aethiopicus (15.1 %). By 1990s the proportion of O. niloticus had decreased to 45.1% while that of P. aethiopicus had increased to 37.6%. These changes seem to have been caused by overfishing resulting from increased fishing effort from the recommended 250 to about 1000 boats and the additional increase in effort through driving fish into the nets by beating water. The maximum size of O. niloticus in the fishery decreased from 32 cm total length in 1975/78 to 22 cm in 1988/92 while the size at first maturity decreased from about 21 cm to 14 cm during the period. This has been concurrent with a shift in the mesh size of gillnet used from 127 mm (5") in 1960s to 64 mm by 1990s. Environmental changes, especially in lake level in 1980, may also have affected the fishery.