摘要:

The statistical treatment of condition used in many previous studies has been to determine a predicted weight for a fish, and to calculate a ratio of actual to predicted weight. The ratios obtained, known as condition factorK, are then further analysed using analysis of variance or other techniques to relate changes inKto other independent variables. It is suggested that condition can be studied better by using a single model to analyse the response of fish weight to a number of factors simultaneously. This approach affords benefit from the simplicity of using an integrated analysis and avoids problems with skewed distributions of ratios. An example using data on the Pacific sardine,Sardinops sagax(Jenyns), is given. Changes in condition of this fish due to monthly, yearly and temperature effects are calculated.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb02629.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

A histological and gravimetric analysis of oocyte development inEncrasicholina heteroloba(Ruppell, 1858) indicated that this species spawns serially and has a group‐synchronous mode of ovarian development. A six stage maturity scale, based on both external morphology and oocyte composition, was proposed to classify ovarian development inE. heteroloba. The incidence of females with hydrated oocytes and post‐ovulatory follicles in samples from two regions; the south Java Sea and Roviana lagoon, in the Solomon Islands were used to estimate spawning frequency. Estimates of mean inter‐spawning intervals ranged from around 2 days in fish from Roviana lagoon to up to 16.7 days in fish from the south Java Sea. Batch fecundity was determined from the number of oocytes in the largest oocyte size class in ripe stage ovaries. Batch fecundity was related to size and was significantly greater for a given size in the Roviana lagoon population (F= 0.081 ×L4.89, Roviana population;F= 1.682 ×L2.83, Jepara popu

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb02630.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

To test the hypothesis that the Japanese eel,Anguillu japonica, elvers in the eastern and western coasts of Taiwan are recruited from two different spawning grounds and to increase the knowledge of the early life history of the eel, the otolith microstructure and daily age of elvers collected from five estuaries in the coast of Taiwan during December 1989 through February 1990 were examined by scanning electron microscopy. The total length of elvers at arrival in the estuaries was similar among estuaries, averagingc. 56.0 mm and showed a seasonal decrease. The maximum radius of the sagittal otolith of elvers ranged from 124.46 to 181.82μm with a mean of 143.15 ± 12.72 μm. The otolith from centre to edge included an organic‐rich primordium (9.20 ± 2.02 μm in diameter), a diffusively calcified core (20.94 ± 1.99 μm), and the daily growth increments; these three layers were probably deposited during the embryonic, yolk sac and feeding period respectively. The growth rate of the otolith was higher at the beginning of early life (0.5−1.0 μm day−1), lowest at approximately 100‐days old (1.0 pm day−1). The mean age for elvers arriving in the estuaries of the coasts of Taiwan was approximately 170.4 ± 21.02 days. Neither the growth pattern of the otolith nor the age of elvers arriving in the estuary were significantly different among estuaries, indicating that the elvers in both eastern and western Taiwan were probably recruited from the same spawning ground. The growth pattern of the otolith in relation to larval m

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb02631.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

A description is given of the seasonal trends exhibited by gonadosomatic indices, gonadal maturation and oocyte diameters of different age classes of the flathead,Platycephalus speculator, in Wilson Inlet, a seasonally closed estuary on the south coast of Western Australia. These data indicate that, although sexual maturity is attained by the vast majority of males at the end of the first year, it is delayed for a further year in females. Breeding occurs predominantly during the summer and early autumn (December to March). The presence of late stage eggs and preflexion larvae between January and March of 1988, when a sand bar was present across the mouth of the inlet channel, demonstrates that this marine species spawns in the estuary. Spawning also occurred within the estuary in the following year, even though the estuary mouth was open during the breeding period. AlthoughP. speculatortypically spawns at sea, spawning in Wilson Inlet takes place at salinities less than 30%, i.e. below full strength sea water. The distribution of oocyte diameters and the presence of mature eggs and post‐ovulatory follicles in the ovaries of many fish indicate thatP. speculatorspawns more than once in a breeding season. Late stage eggs ofP. speculatorare pelagic,ca0.8 mm in diameter and possess embryos with an unpigmented yolk sac containing a single, pigmented oil globule. The larvae are pelagic and characterized by a relatively large and wide head bearing a series of spines, a moderately long gut, an elongated and compressed tail, large fan‐shaped pectoral fins and 25 or 26 myomeres. Flexion of the notochord occurs between 5 and 7 mm and settlement takes place at approximately 13

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb02632.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Freshwater tilapia feeding on a diet containing 1 mmol kg−1magnesium (control diet: 30 mmol kg−1) grow although at a decreased rate. The diet does not noticeably affect the blood ionic composition. Prolactin cell activity increases in these fish as judged from the enhanced rate of synthesis of3H‐leucine labelled prolactinsin vitroand the ultrastructure of the cells. Na+intake and Na+loss decreases, and chloride cell density increases, phenomena typical for enhanced prolactin cell activity in tilapia. We conclude that tilapia manage to cope with a dietary magnesium insufficiency and suggest that prolactin is involved in the acclimation to this

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb02633.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Porcine galanin, somatostatins (SRIF‐25 and SRIF‐28) and invariant SRIF‐14, known to have inhibitory‐stimulatory actions on growth hormone (GH) secretion in higher vertebrates, were tested for their ability to affect plasma GH levels in coho salmon. Peptides were administered by intraperitoneal injection of 10 or 100 ng g−1body weight. All three SRIFs decreased plasma GH concentrations, their activity following the order SRIF‐14>SRIF‐28>SRIF‐25. Galanin and an anti‐SRIF produced pronounced, although transient incre

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb02634.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Individual grass carp,Ctenopharyngodon idellu, were maintained in a respirometer for a month and fed pelleted diets containing various proportions of carbohydrate, fat and protein at different ration levels. Oxygen consumption was measured continuously, allowing the effects of consecutive daily feeding on respiration to be studied. The relationships established between daily food intake and oxygen consumption showed that, on average, 23.3% (high protein diet), 15.3% (high carbohydrate diet), 20.7% (high lipid diet) and 7.0% (Lemnu diet) of the absorbed energy was partitioned into specific dynamic action (SDA). (Here the term SDA is used to describe the oxygen consumption of a feeding fish in excess of the routine metabolic rate.) In terms of the overall energy budgets of growing fish, SDA represented between 12 and 58% of the total heat lost over the experimental period and was equivalent to between 14 and 33% of the consumed energy. Ration was positively correlated with heat loss due to total respiration (r= 0.881) and with heat loss due to SDA (r= 0.762). As ration increased, the size of SDA relative to total respiration increased. Significant positive correlations were found between oxygen consumption (total or due to SDA) and specific growth rate, and between oxygen consumption and the deposition of protein and energy. However, growth rate had a minimal influence on daily oxygen consumption when compared with food intake.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb02635.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

In Lake Constance from September 1986 to May 1988 13 adult lake dwelling brown trout (Sulmo truttaL.) were tagged with ultrasonic transmitters and tracked almost continuously for up to 13 days. Two behaviour types were observed: (a) random movement in locally restricted areas and (b) excursions of up to 40 km distance. Swimming activity during the day was significantly higher than at night in most experiments. In summer swimming depth ranged between 8 and 16 m, and in winter between 0 and 3m. The preferred water temperature was about 14°C in the thermally stratified waterbody. During the experiments mean swimming speed ranged between 0.3 km h−1(0.1 bodylengths s−1) and 0.9 km h−1(0.6 bodylength

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb02636.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The intracellular localizations ofchitinase and β‐N‐acetylglucosaminidase were detected in turbot blood smears, using a novel method employing fluorogenic substrates. The two enzymes showed different distributions, with chitinase being more generally distributed and N‐acetylglucosaminidase being strongly associated with distinct intracellular bodies, probably lysosomes. The fluorogenic substrates were used to analyse soluble and membrane fractions of homogenates of red and white blood cells prepared on Percoll gradients. In the leucocytes, the chitinase and N‐acetylglucosaminidase activities were mostly in the soluble fraction. In the erythrocytes the activities were lower, at about one‐hundredth and one‐tenth specific activities, respectively, and were distributed between soluble and membrane‐bound fractions at about 2 : 1 and 3 : 1, respectively. In contrast, lysozyme had a soluble distribution in leucocytes and was not detected in erythrocytes. Plasma was rich in chitinase and lysozyme activities but had no detectable N‐acetylglucosaminidase. Two possible roles for the chitinolytic enzymes are discussed: defence against pathogens and processing of glycoproteins or glucosaminoglycans. Evidence for a defence role for the chitinase and lysozyme is provided by demonstrating that they had inhibitory activity against the chitinous fu

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb02637.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Age and growth of an Iberian cyprinodont,Aphanius iberus(Cuv.&Val.), in its most northerly population, La Rubina lagoon (Alt Empordà wetlands, NE Spain), was studied. The age groups for this Mediterranean population (O +, 1 + and 2 +) agree with those reported for the Atlantic population (R. Guadalquivir marshes), in the southern limit of the species distribution in the Iberian peninsula. Differences in age structure between these populations and the one previously studied in La Tancada lagoon (R. Ebro delta marshes) can be attributed to age estimation bias. MaleA. iberusdata appear to fit similarly to a Gompertz growth function and to a von Bertalanffy growth function, butLx, was clearly underestimated. A Gompertz growth function was not a good fit for females, perhaps because female growth is clearly faster and less attenuated than male growth. The life history and growth pattern ofthis species is similar to that in other cyprinodontiform fishes, typified by a short longevity. The growth model of this species does not seem to fit types I and II of Sebens's classification, which are characteristic of fish

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb02638.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY