The age and growth of the tongue sole Cynoglossus canariensis (Steind 1882)

The geometric mean regression equation for the weight; length relationship of Cynoglossus canariensis was W = 0.0025 L super(3.1770). The Von Bertalanffy constants Woo, Loo, K, and to were 507.5852 g, 47.3683 cm, 0.3333 and 0.1397 for males and 839.0753 g, 54.4720 cm, 0.3062 and 0.1737 for females. Total mortality coefficient Z ranged from 0.6482 and 0.8021

Fishing gear survey of Kainji Lake, northern Nigeria, 1996

A survey was carried out in September 1996 alongside the annual frame survey of Kainji Lake, Nigeria. As in the previous surveys, there were 6 main fishing gear types in use on the lake, which included gill nets, drift nets, beach seines, cast nets, longlines (baited and foul hooking) acid fishing traps. A total of 813 canoes were sampled. The canoe lengths were similar to the previous gear surveys. Altogether 466 gill nets were measured. They had an average length of 149 m, and were mostly bottom set. Of the gill nets measured 68% had a mesh size below 3 inches the minimum mesh size allowable according to the Niger and Kebbi State Fisheries Edict, 1996. Of concern was the large increase in the number of 1 inch meshed nets recorded on the lake. Drift nets had a mean length of 74 m. A total of 88% of all drift nets measured had a mesh size below 2.5 inches, the minimum mesh size stipulated in the State Edict. A total number of 102 beach seines were sampled with a mean length of 110 m, the mesh size in use on the lake remained as 0.1 inches under the Edict beach seines are banned from fishing in Kainji Lake. The decline in the lengths of the beach seines (and therefore catch rates) recorded since l995 was encouraging in the light of the destructive nature of these nets. A total of 30 cast nets were sampled, they had a mean diameter of 9.8 and a mean mesh size of 1.9 inches. All the nets had a hanging ratio of 0.5. Of the cast nets measured 40% had a mesh size below the minimum size of 2 inches recommended by the State Fisheries Edicts. Of concern was the continued rise in the number of gill nets with mesh sizes less than 2 inches. There were 2 types of longlines in operation on the lake. The baited and the foul hooking longlines. They were mostly bottom set and the hook size nos. 12-14 (Kirby sea hook) were predominant. Two types of fishing traps were identified, one was covered with a mesh of thin cane, one with netting material. The fishing traps had a mean height of 0.8 m and a mean width at the vase of 0.53 m. The mean mesh size used was 0.86 inches. Citharinus was reported as the most targeted of all fish species on the lake. Synodontis membranaceous was also targeted by most gears especially the smaller meshed nets. Labeo and Tilapia were low on the list of targeted species but their incidence remains high in the catches. (PDF contains 27 pages)

On the methods of determining size/weight characteristics of food organisms of fish. (Determination of the length of Copepoda in larval stages by egg-laying females of the free living freshwater Copepoda). [Translation from: Voprosy Ikhtiologii 14, 182-194, 1960. ]

As is known, copepods play an important role in the nutrition of fish. Therefore with a view to facilitating research on the study of the quantitative side of feeding, there have recently appeared a considerable number of papers devoted to the development of methods for determining the wet. weight of these crustaceans. For the further facilitating of research in the nutrition of fish it would be of great interest to clarify the problem, is there not some kind of rule in the growth of the crustaceans during metamorphosis, and if there is such a rule is it not possible, to determine the length of the larvae at each stage, not by measuring them, but by using the formulae derived on the basis of these rules. This article examines the growth curves of different species of freshwater Copepoda, obtained on the basis of experimental observations in cultures or by way of measurement of mass material at all stages of development in samples from water-bodies. The authors study in particular the ratio of the mean diameter of the eggs to the mean length of the egg-bearing females.

Episodic variations in stream water chemistry associated with acid rainfall and run-off and the effect on aquatic ecosystem, with particular reference to fish populations in N.W. England

This is the episodic variations in stream water chemistry associated with acid rainfall and run-off and the effect on aquatic ecosystems, with particular reference to fish populations in North West England produced by the North West Water Authority in 1985. This report looks at the biological, physical and chemical information collected over a five year period from over 100 sites on upland streams in the North West Region of which drained rocks of low buffering capacity. In both Lake District and South Pennine sites striking differences were found between the composition of invertebrate communities inhabiting acid-stressed and less acid-stressed streams. Electric fishing surveys showed that acidic streams (geometric mean pH <5.5) generally had abnormally low densities of salmonids ( < 0 .2m2) and that 0+ fish were very few or absent. The latter indicates recruitment failure. Salmon were more sensitive than trout to low pH.

Age and growth of blue rockfish (Sebastes mystinus) from central and northern California

Otoliths from blue rockfish (Sebastes mystinus), were aged by using a combination of surface and break-and-burn methods. The samples were collected between 1978 and 1998 off central and northern California. Annual growth increments in the otoliths were validated by using edge analysis for females up to age 23 and for males to age 25.The first annual growth increment was identified by comparing the diameter of the otolith from fish known to be one year old collected in May (when translucent zone formation was completed) to the mean diameter of the first translucent zone in the otoliths from older fish. Our estimated maxi-mum ages of 44 years for males and 41 years for females were much older than those reported in previous studies. Von Bertalanffy growth models were developed for each sex. Females grew faster and reached larger maximum length than males. The growth models were similar to those generated in other studies of this species in southern and central California. Fish from northern and central California had similar maximum sizes, maximum ages, and growth model parameters.

On further improvement of the techinque of evaluating summer institutes

Data from an earlier study are reanalyzed to improve upon the evaluation measures of summer institutes. The Summer Institute Efficiency Index is improved by using weighted geometric mean using different ranks as weights for the several dimensions. The coverage utility index is improved by taking the ratings given by all the participants.

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.

Some aspects of the ecology of the leatherback turtle Dermochelys coriacea at Laguna Jalova, Costa Rica

The ecology and reproductive biology of the leatherback turtle (Dennochelys coriacea) was studied on a high-energy nesting beach near Laguna Jalova, Costa Rica, between 28 March and 8 June 1985. The peak of nesting was between 15 April and 21 May. Leatherbacks here measured an average 146.6 cm straightline standard carapace length and laid an average 81.57 eggs. The eggs measured a mean 52.12 mm diameter and weighed an average of 85.01 g. Significant positive relationships were found between the carapace lengths of nesters and their clutch sizes and average diameter and weight of eggs. The total clutch weighed between 4.02 and 13.39 kg, and yolkless eggs accounted for an average 12.4% of this weight. The majority of nesters dug shallow (<24 cm) body pits and spent an average 81 minutes at the nest site. A significant number of c1utcbes were laid below the berm crest. In a hatchery 42.2% of the eggs hatched, while in natural nests 70.2% hatched. The average hatchling carapace length was 59.8 mm and weight was 44.6 g. The longevity of leatherback tracks and nests on the beach was affected by weather. One nester was recaptured about one year later off the coast of Mississippi, U.S.A. Egg poaching was intense on some sections of the Costa Rican coast. Four aerial surveys in four different months provided the basis for comparing density of nesting on seven sectors of the Caribbean coast of Costa Rica. The beach at Jalova is heavily used by green turtles (Chelonia mydJJs) after the leatherback nesting season. The role of the Parque Nacional Tortuguero in conserving the leatherback and green turtle is discussed.(PDF file contains 20 pages.)

Sexual maturity, fecundity and egg size of wild and cultured samples of Bagrus bayad macropterus

Twenty four matured samples of Bagrus bayad macropterus from the wild (Shiroro Lake, Nigeria) and under captivity, size ranging from 412.69-3300.00 g total body weight, were analysed for sexual maturity,fecundity and egg size. The average fecundity obtained were 53352.59 and 21028.32 eggs for the wild and cultured fish respectively.Positive relationship was observed between fecundity, body size and gonad weight. Fecundity increased as body size increased. A more positive and linear relationship was observed between fecundity and gonad weight than fecundity and total body weight. Egg diameter,length and weight were determined from the egg samples. The mean size range of eggs for cultured fish was 0.74-1.05 mm of diameter; 1.01-1.20 mm of length and 0.25-0.40 mg of weight. Wild samples had mean size range of 0.68-l.09 mm of diameter, 0.85-1.38 mm of length and egg mean weight range was 0.15- 0.40 mg. Sexual maturity is dependent on size (1 kg and above). The egg diameter, egg length and weight bear no relationship with each other. Gonad development study indicated that gonad development was faster under captivity than in wild

Observations on the ecology of Hepsetus odoe, Bloch, 1794 (Pisces: Hepsetidae) in Epie Creek floodplain, Niger Delta, Nigeria

The distribution, abundance, age and growth, the food and feeding habits, condition factor and reproduction of Hepsetus odoe in the Epie Creek Floodplain (Nigeria) was studied. H. odoe occur in the creek, swamp channel and lake. It is a very common, abundant and one of the major commercial species. A total of 457 specimens weighing 76.90 kg were caught during the period of investigation. The catches were more abundant in the dry season than in the wet season. The total length ranged from 10 cm to 46 cm while the weight varied between 50 g and 900 g. Six distinct components or year classes were observed using Bhattacharya's method. A growth exponential value 'b' was 3.35 with condition factor, 'k' values ranging from 0.69 to 0.83. The main diets of Hepsetus odoe were fish, including crustaceans (shrimps) and insects. The mean fecundity was 6060 plus or minus 358 eggs (range 2,769 to 6.667 eggs). The ova diameter of H. odoe was found to range from 2.2 mm to 2.6 mm with overall mean = 2.4 plus or minus 0.1)

Relationship between the basic morphometric measurements and growth pattern of Heterotis niloticus from River Kaduna floodplain

A total of 61 specimens of Heterotis niloticus were evaluated by linear regression and correlation. The specimens had mean standard length of 27.09 plus or minus 4.73cm, total length of 33-49cm, mean weight of 2445,108.3g, mean snout length of 48 plus or minus 0.86cm, mean eye diameter of 1.30 plus or minus 0.15cm, mean head length of 6.29 plus or minus 1.75cm. There was a strong relationship between the length and the weight, the eye diameter and the standard length, snout length and the standard length, head length and the standard length, snout length and the weight, head length and the weight (P<0.05). But the correlation of the eye diameters and the weight was insignificant (P>0.05). The growth pattern analysis depicts that the growth was negatively allometric with a b value of 1.16

Trenngitter - eine Alternative zu den Trichternetzen in der Garnelenfischerei

Experimental fishing trials were conducted in the Elbe Estuary using an experimental 3 m-standard beamtrawl. To avoid the by-catch of fish, a sorting grid was used. The elliptical grid was constructed of 6 mm diameter stainless steel bars with a spacing of 13 mm between the bars and housed in a cylindrical frame of 400 mm diameter. It was installed in the extension piece just in front of the codend angled at 45°, with a fish outlet at the top. A series of 10 tows of 15 minutes duration at a towing speed of 3 kn was done. The catch of the main codend was compared with the catch separated by the sorting grid. This achieved a reduction of 56 % of plaice (Pleuronectes platessa), 75 % of flounder (Platichthys flesus), 99 % of whiting (Merlangius merlangus), 94 % of cod (Gadus morhua) and 49 % of smelt (Osmerus eperlanus) with a mean loss of 43 % of shrimps (Crangon crangon). English grid trials in the Humber estuary using a flapper set or guiding funnel in front of the sorting grid device demonstrated reasonable lower escapement rates for fish and shrimps.

Surface water temperature of Windermere. Monthly and yearly totals of degree-days centigrade and monthly mean temperatures, 1933 to 1975

The surface temperature of Windermere has been recorded by the staff of the Freshwater Biological Association on every weekday (with a few minor exceptions) since 11 January 1933. This publication presents this information in a form which can easily be used by individual research workers. There are 43 tables (1 for each year, 1933-1975) which give the data, expressed as degree-days centigrade. The tables show for each month the number of degree-days above each temperature from 0 degree C to the highest recorded, at 1 degree C intervals. Mean temperatures are obtained by dividing the number of degree-days over 0 degree C by the relevant number of days. The advantage of degree-days rather than mean temperatures is that degree-days are additive so data for any desired periods may be combined quickly and simply. Seasonal results for spring, summer, autumn and winter are presented in tabular form, as are selected totals for comparisons between years. Further tables give the mean temperature in each month of the year, and the frequency distributions of monthly mean temperatures.

Advances in methods for determining fecundity: application of the new methods to some marine fishes

Estimation of individual egg production (realized fecundity) is a key step either to understand the stock and recruit relationship or to carry out fisheries-independent assessment of spawning stock biomass using egg production methods. Many fish are highly fecund and their ovaries may weigh over a kilogram; therefore the work time can be consuming and require large quantities of toxic fixative. Recently it has been shown for Atlantic cod (Gadus morhua) that image analysis can automate fecundity determination using a power equation that links follicles per gram ovary to the mean vitellogenic follicular diameter (the autodiametric method). In this article we demonstrate the precision of the autodiametric method applied to a range of species with different spawning strategies during maturation and spawning. A new method using a solid displacement pipette to remove quantitative fecundity samples (25, 50, 100, and 200 milligram [mg]) is evaluated, as are the underlying assumptions to effectively fix and subsample the ovary. Finally, we demonstrate the interpretation of dispersed formaldehyde-fixed ovarian samples (whole mounts) to assess the presence of atretic and postovulatory follicles to replace labor intensive histology. These results can be used to estimate down regulation (production of atretic follicles) of fecundity during maturation.