Allometric growth and sperm competition in fishes

The allometric relationship between body mass and gonad mass in males of 23 fish species from 11 families was examined. There was no evidence of a single allometry for all fishes. A cross species analysis suggested a scaling coefficient of 1·04, which was significantly different from a previous study that reported a scaling coefficient of 0·904. A within species analysis generated scaling coefficients from 0·68 to 3·90. Furthermore, for those species characterized by alternative mating tactics, there was no correlation between the scaling coefficients of bourgeois‐type males and parasitic‐type males. These results are discussed in the context of the gonado‐somatic index and its use in testing sperm competition theory.     

Seasonal variations in the physiological status and energy content of somatic and reproductive tissues of chub

The seasonal fluctuations in condition, nutrition and somatic energy content, and gonad development cycle were investigated in chub Leuciscus pyrenaicus from the headwaters of the Guadalete River, a freshwater ecosystem characterized by strong seasonal fluctuations in discharge and water level, temperature and food supply. The relationship between somatic stage and gonad cycle was also investigated and discussed. Condition, nutrition and somatic energy cycles could be divided into two distinct periods: from April to January with summer decreases and autumn increments, which is common for juveniles and mature fish; and from January to March, when juveniles and mature fish displayed different temporal variations related to the reproductive cycle. Gonad development took place from the end of the winter into the summer, the testes developing before the ovaries. Spawning started in late spring (May) and continued into summer (June and July), with fish quiescent by autumn (September). The results suggest that, for L. pyrenaicus , both environmental factors (e.g. food supply, water temperature) and reproduction needs affect the condition, nutrition and somatic energy storage of fish, which have been used as indicators of the physiological status of the population.     

Reproductive biology, length-weight relationship and relative condition of pond raised Tilapia zilli (Gervais)

In 'runted' populations of Tilapia zilli positive correlations were found between maturation stages and the following: gonadosomatic index, gonad weight, fish weight and fish length. The minimum size at maturity was 9·0 cm in males and 11·0 cm in females. The mean fecundity in the 'stunted' females was 2359 eggs and it increased with length ( L ) weight (HO and depth ( D ) of the fish. There was, however, no correlation between fecundity and egg size. The results indicated that growth in this 'stunted' T. zilli population was not isometric. The relative condition factor ( Kn ) which approached one indicates good condition.     

The determination of age and growth from the scales in Barbus liberiensis (Pisces, Cyprinidae)

The predictability of scale check formation in Barbus liberiensis has been investigated. Scale length is shown to be linearly related to body length. The formation of the check can be interpreted in terms of the reproductive cycle and changes in somatic condition. Throughout the population check formation takes place in two phases, resorption of material from the scale edges coinciding with the early and middle phases of gonad maturation, and the formation of the check itself as a result of repair as maturation is completed. Check formation is not correlated with actual spawning activity and fluctuations in food intake and temperature are insignificant.
The first scale check is formed at the end of the first year and from analysis of check frequency the mean body lengths at the end of the first, second and third years were 6·9 cm, 8·3 cm and 9·3 cm. There was no significant difference in the growth rate of males and females although the females tend to live longer and therefore attain a greater maximum size. Some individuals may not have formed a check at the end of the first year.
The difference between check formation in tropical and temperate fish and also between forest and savanna types are discussed. The predictability and the factors affecting check formation in tropical freshwater fish are considered.     

Seasonal changes in condition, nutrition, gonad maturation and energy content in barbel, Barbus sclateri, inhabiting a fluctuating river

The objective of this study was to investigate the seasonal cycle of condition, nutrition and gonad development, as well as the magnitude of seasonal variations in energy content of somatic and gonad tissues in juveniles, males and females of Sclater's barbel, Barbus sclateri, from the upper Guadalete River (south Spain). The influence of reproductive cycle on somatic changes was also investigated and discussed. Measurements of condition factor (K), somatic index (SI), gonadosomatic index (GSI) and somatic and gonad energy content (J g^-1 dw) were made in individual specimens taken from the Guadalete River monthly for 12 months. This freshwater ecosystem is characterised by strong seasonal fluctuations in water and flow level, temperature and food supply. It was found that in general juveniles, males and females of barbel exhibited a similar condition, nutrition and somatic energy cycle throughout the year, with the highest values in spring and the lowest in summer. Depletion of K, SI and somatic energy storage from spring until mid-summer seems to be associated with high metabolic demands during this period, and in adult fish also with spawning-related activity. The gonad index and energy content of the gonad were the highest in April and the lowest in summer for both sexes. Spawning took place during late spring – early summer, with fish quiescent by mid summer. The energy required for ovarian development (3970 J g^-1 dw) was greater than the one for testes development (2763 J g^-1 dw). Data on gonad energy content indicated a period (March to April) of intense energy accumulation (64% males and 37% females) which was related to the decline in the average somatic energy content in males and females. The somatic energy content was linearly related to K and SI. In the same way, GSI correlated positively with gonad energy. Linear trends were found between somatic parameters (K, SI and energy content) and gonad parameters (GSI and energy content). This revised version was published online in July 2006 with corrections to the Cover Date.     

Body composition and energy allocation in life-history stages of brown trout

Energy contents of immature parr and smolts, and mature resident and anadromous brown trout Salmo trutta sampled from a small stream in southern Norway were estimated from lipid, protein and carbohydrate concentrations. In immatures the lipid concentrations were highest in parr in the autumn. Mean lipid concentrations increased significantly with age in parr sampled in autumn (1·3% in age 0+ to 3·4% in age 3+), whereas they did not in smolts. The lipid concentrations of parr in spring were not significantly different from those of similarly aged smolts. By contrast, the relative water content (%) decreased with age in parr in the autumn and increased with age in smolts, mean values being slightly higher in smolts (78%) than in parr (77%). Protein and carbohydrate concentrations did not vary with age in the immature fish, mean protein concentrations being 18·0, 17·5 and 16·8% in parr in the autumn and spring, and in smolts, respectively. In residents, the concentrations of lipids were lower and of water higher, in age group 1 than in older fish, whereas there was no significant variation with age amongst anadromous trout. The energy concentration of 2+ smolts (349 kJ 100 g^-1) was similar to that of 0+ parr in the autumn. Mean somatic energy density in autumn was 1·1 times higher in freshwater residents than in parr at age 1+ (407 and 387 kJ 100 g^-1) and marginally different at age 2+ (462 and 426 kJ 100 g^-1, respectively). The energy contents per unit mass of residents were 1·3–1·6 times that of similar aged smolts. Mean somatic energy density of anadromous trout (504 kJ 100 g^-1) was higher than that of residents (455 kJ 100 g^-1). Somatic energy, lipid and protein concentrations were correlated highly with water contents of all life stages, age and sex groups.     

Analysis of the factors related with mate choice and reproductive success in male three-spined sticklebacks

Territorial three-spined sticklebacks moved 5·3 times as far as non-territorial males in 2 min ( P < 0·001) and spent 11·1 times longer in aggression in the pools ( P < 0·001). Territorial males had slightly higher condition factors than non-territorial males. Condition factor was correlated positively with the gonad mass ( P < 0·006), carotenoid concentration ( P < 0·006) and the activity of CS in the axial muscle ( P < 0·05) and lactate dehydrogenase (LDH) in pectoral muscle ( P < 0·003). The male traits best correlated positively with female mate choice were courtship effort ( P < 0·001), coloration ( P < 0·003) and initial condition ( P < 0·025). Courtship behaviour was related to intestine mass ( P < 0·018), axial ( P < 0·028) and pectoral muscle citrate synthase (CS) activity ( P < 0·047); coloration was related to gonad mass ( P < 0·037). These muscle enzymes may be involved in ATP generation for sustained activities or in recuperation between bouts of burst activity. Females that choose to mate with assiduously courting males which bear higher CS levels may be choosing individuals that show honestly their good condition and capacity to accomplish reproductive tasks.     

Life history of Maurolicus muelleri in fjordic and oceanic environments

Life history parameters are compared for populations of Maurolicus muelleri from Norwegian fjords and the Norwegian Sea in 1995 and 1996. The mortality rate was higher in the oceanic population (2·55 for males, 2·00 for females) than in the fjords (1·15 for males, 0·97 for females). Fish from the Norwegian Sea population occupied a depth with higher light levels, which may have contributed to the higher mortality through increased visibility to predators. Differences in growth, condition and gonad weight indicated different resource levels caused by different population densities. Recruitment was weak in many fjords in 1994, but not in the Norwegian Sea. It is suggested that wind-generated advection may affect recruitment in fjords on the western coast of Norway.     

Reproductive biology of the threatened golden galaxias Galaxias auratus Johnston and the influence of lake hydrology

Golden galaxias Galaxias auratus (31–235 mm fork length, L _F) were collected monthly from littoral habitats in Lakes Crescent and Sorell, Tasmania, Australia, between July 2000 and December 2002. Spawning habitats were identified and monitored in both lakes, and surveyed in Lake Crescent. Trends in gonado-somatic indices and reproductive stages of development indicated that gonad development in both sexes begins in midsummer and peaks in late autumn to early winter. Males mature at smaller sizes (50% at 52 mm L _F) than females (50% at 76 mm L _F), larger individuals are predominately females (95% of fish ≥138 mm L _F), and overall male to female ratios are female biased ( c . 1:2). Spawning occurs late autumn to early spring (water temperatures = 1·4–9·7° C) with peaks in spawning activity in winter (mean water temperatures <5° C). Demersal adhesive eggs ( c. 1·5 mm diameter) were found on cobble substrata ( c. 20–250 mm diameter) in littoral areas ( c. 0·2–0·6 m deep) and fecundity of fish 71–181 mm L _F ranged from 619 to 14 478 eggs. The rate of change in water level over the 20 days prior to monthly sampling was important in explaining the occurrence of spent fish and this accounted for temporal differences in spawning between the populations. Lake hydrology influences the reproductive cycle of G. auratus by possibly providing a stimulus for spawning and it controls the availability of spawning habitat in Lake Crescent. Seasonal hydrological cycles ( i.e. rises during late autumn to winter) and a minimum water level of 802·20 m Australian Height Datum in Lake Crescent during autumn (above which littoral areas of cobble substratum are inundated) are critical to G. auratus populations.     

Transgene activity following somatic transgenesis in Nile tilapia Oreochromis niloticus

A detailed study was made of the persistence and expression of a plasmid-enclosed reporter gene construct after intramuscular injection into the somatic muscle tissue of juvenile Nile tilapia Oreochromis niloticus and also the effect of injecting a potentially growth-promoting gene construct. The plasmid-enclosed DNA proved stable at the site of injection, lasting in some cases for up to 6 months, and was, at a very low frequency, detected in gonad tissue, indicating occasional substantial movement from the injected muscle site. It was observed that the reporter gene and regulatory sequences were also functional within the somatic cells. In a comparison of expression levels by direct somatic injection, the 1·6 kb tilapia β-actin regulatory sequence (tiβAP) resulted in c. three-fold higher β-galactosidase activity than the 4·7 kb carp β-actin regulatory sequence (cβAP) when spliced to the lacZ gene. The enhancer element near the end of first intron in the tiβAP, when co-injected with tiβAP/lacZ plasmid at a 3:1 ratio, drove significantly higher reporter activity in somatic cells than the tiβAP/lacZ sequence alone. The introduction of a growth-promoting construct, the Nile tilapia growth hormone gene driven by a tiβAP, yielded no detectable growth enhancement.     

Seasonal variation of thermophilic campylobacters in lambs at slaughter

A survey of the isolation rate and population size of thermophilic campylobacters in lambs at slaughter was carried out to determine the seasonal variation of thermophilic campylobacters in ovine hosts. Isolation rates determined by enrichment methods were always higher than those using direct plating onto selective agar and showed that Campylobacter could be isolated from 91·7% ( n = 360) of samples from the small intestine of the lambs. Enumerations (MPN), done monthly over a 2-year period, averaged 4·00 log 10 ( n = 1080, S.D . 0·16) campylobacters g⁻¹ fresh weight (fw) intestinal contents with some samples giving values higher than 7 log MPN gfw⁻¹. These results show that the prevalence of thermophilic campylobacters in sheep intended for slaughter is much higher than previously reported. Statistical analyses showed that there was a significant seasonal periodicity in the Campylobacter populations in the small intestines of lambs at slaughter ( P = 0·004) but that there was no statistical relationship with environmental parameters such as minimum and maximum temperature, rainfall or hours of sunshine. In an analysis along the length of the intestinal tract of lambs, campylobacters were isolated from 80% of small intestine and 30% of rumen samples, but not from the true stomach, large intestine or caecal samples. A survey of sheep grazing on salt marsh, fell (upland) and farm pasture showed that the isolation rate of thermophilic campylobacters in fresh faeces was substantially lower (29·3% ( n = 420)) than that from the small intestine of lambs at slaughter. No significant difference (>0·05) was found between the isolation rate of campylobacters from faeces sampled in late spring/early summer and autumn, nor between the different types of grazing.     

Effects of confinement stress of variable duration on the growth and microincrement deposition in the otoliths of Oreochromis niloticus(Cichlidae)

The effects of chronic confinement stress (1, 5 and 10 days) and of periodic blood sampling on somatic growth and the structure and growth of otoliths was studied in Oreochromis niloticus . During the study, the plasma concentrations of cortisol were measured at various times during the application of stress: they were significantly higher in confined fish than in control fish (mean ±  s . d . 3·40 ± 0·47 v . 1·26 ± 0·62 ng ml⁻¹, P  < 0·05) up to 5 days after the start of a 10 day stress period. The somatic growth (standard length, L _S, and mass) was affected by the confinement and by the sampling (from 16·21 ± 1·07 to 14·64 ± 1·15 cm for L _S, and from 173·31 ± 33·14 to 110·50 ± 29·48 g for mass). But the confinement masked the effect of the sampling on somatic growth. Tetracycline was injected at the start of the experiment to mark the otoliths, and showed that the short and long duration confinements led to a clear check in the pattern of primary increments in the otoliths. The number of primary increments deposited during the resting periods that followed each period of confinement was always less than the number of days that these periods lasted. No relation was found between the duration of confinement and the structure of the resulting checks. These results suggest that there is a disruption in the laying down of primary increments during periods of confinement resulting in an underestimation of their number compared to the actual number of days of growth. These results call into question the use of otolith primary increments as a means of estimating the age of Nile tilapia that have experienced periods of stress.     

Allocation of pyloric caecum reserves in FED and starved sea stars, Pisaster giganteus (Stimpson): somatic maintenance comes before reproduction

Pyloric caeca were removed through the raytips of sea stars, Pisaster giganteus (Stimpson), beginning their seasonal period of gonad growth. Four months later their feeding rate, gonad growth, and gametogenic activity were lower than those of intact animals, while body growth rate remained the same. Removal of only the raytips also depressed feeding rate and gonad growth. When sea stars were starved, gonad growth and gametogenic activity were lower in animals without pyloric caeca, but body weight loss was the same as in intact animals. We conclude that when food is abundant, materials are utilized to enhance somatic and gonad growth. With decreasing reserves, due either to reduced food intake and/or pyloric caecum removal, somatic maintenance and growth have priority over gonad growth in material and energy allocation. Such a pattern of resource allocation is appropriate for long-lived iteroparous animals, such as these sea stars.     

Bacteriophages of enteric bacteria in drinking water, comparison of their distribution in two countries

The presence of bacteriophages infecting enteric bacteria was tested in more than 1500 drinking water samples in Israel and Spain. Bacteriophages tested were somatic coliphages, F-specific bacteriophages and Bacteroides fragilis bacteriophages. The three groups of bacteriophage were isolated in 100 ml water samples by the presence/absence test with similar frequencies, which ranged from 4·4% for somatic coliphages to 6·1% for bacteriophages infecting Bact. fragilis. In contrast, the frequency of isolation of bacteriophages was significantly higher than the frequency of isolation of faecal coliforms, which averaged only 1·9%. No significant differences were observed between the frequencies of isolation between the samples tested in Spain and those tested in Israel. The percentage of groundwater samples containing faecal coliforms and somatic coliphages was reduced significantly by chlorination, despite known deficiencies. However, there was no effect on the occurrence of F-specific bacteriophages and Bact. fragilis bacteriophages.     

Seasonal changes in condition indices in adult mature and non-maturing burbot, Lota lota (L.), in the north-eastern Bothnian Bay, northern Finland

The population structure and seasonal changes in condition factors of the burbot in a shallow coastal region of the north-eastern Bothnian Bay are described. The significance of the so-called rest years is examined by comparing condition indices in immature or sterile and mature burbot. The somatic condition index ( K ₂), liver index ( K ₁), intestine index ( K ₁) and gonad index ( K_g ) are determined monthly in terms of organ weight in relation to body length. Approximately 30% of the whole catch of 1052 burbot were non-maturing but were 40 cm or more in length. K ₂, K ₁ and K ₁ were lowest in the autumn, when the first sign of gonad recrudescence was observed in mature burbot. The non-maturing burbot were never in poorer condition than mature ones. As mature and non-maturing burbot dissipated their energy stores during the warmest period of the summer, it is concluded that burbot spending a rest year do not accumulate and store energy reserves over the summer for the next year, and that such rest years, if they exist, do not occur for nutritional reasons.     

Biochemical composition,condition index,and energy value of Ostrea peulchana (D'Orbigny): relationships with the reproductive cycle

Seasonal changes in body weight, biochemical composition, energy value, and condition index of Ostrea puelchana (D'Orbigny, 1846) from Laguna Punta Cero (Chubut, Argentina), were studied between February 1983 and April 1984. These values were determined for the soft tissues of the whole animal and, separately, from the adductor muscle, digestive gland-gonad complex, and a fraction containing all remaining organs. The main muscle components were proteins whereas glycogen and lipids were stored in the digestive gland-gonad complex. Weight and energy reserves decreased in winter during the beginning of the reproductive cycle and starvation period. In spring, there was a rapid growth of the gonad coincident with an increase in glycogen, lipid, and protein contents. In summer the glycogen content decreased with spawning, and proteins showed the highest values. The glycogen index appears to be suitable as an indicator of the physiological state. During the post-spawning period, in the autumn, the animals attained their best condition in quantity of flesh with a shigh energy value.     

The reproductive cycle of female Ballan wrasse Labrus bergylta in high latitude,temperate waters

This 2 year study examined the reproductive cycle of wild female Ballan wrasse Labrus bergylta in western Norway as a precursor to captive breeding trials. Light microscopy of ovarian histology was used to stage gonad maturity and enzyme‐linked immuno‐absorbent assay (ELISA) to measure plasma concentrations of the sex steroids testosterone (T) and 17β‐oestradiol (E₂). Ovarian recrudescence began in late autumn to early winter with the growth of previtellogenic oocytes and the formation of cortical alveoli. Vitellogenic oocytes developed from January to June and ovaries containing postovulatory follicles (POF) were present between May and June. These POF occurred simultaneously among other late maturity stage oocytes. Plasma steroid concentration and organo‐somatic indices increased over winter and spring. Maximal (mean ±s.e .) values of plasma T (0·95 ± 0·26 ng ml^?1), E₂ (1·75 ± 0·43 ng ml^?1) and gonado‐somatic index (I_G; 10·71 ± 0·81) occurred in April and May and decreased greatly in July when only postspawned fish with atretic ovaries occurred. Evidence indicates that L. bergylta are group‐synchronous multiple spawners with spawning occurring in spring and peaking in May. A short resting period may occur between late summer and autumn when previtellogenic oocytes predominate and steroid levels are minimal.     

Reproductive characteristics of the male herring in the northern Baltic Sea

The gonad weight and gonadosomatic index of the male Baltic herring Clupea harengus membras L., were highest at the beginning of the reproductive season (April/May), the values decreasing towards the end of it (July/August) during 1988–1991. The decline could not be explained by fish size but may have been due to fish condition. A high individual variation was typical for both gonad weights and gonadosomatic indices in fish of the same size and maturity stage. The mean density of sperm cells was significantly higher in June (34·9 × 10⁹ ml⁻¹) than in July (19·2 × 10⁹ ml⁻¹, Mann-Whitney U= 17; P<0·05), the variation among the males being high in both groups. Electron microscope analysis showed a severe disruption of the mitochondrial elements in males spawning at 22°C.     

Latitudinal variability in lunar spawning rhythms: absence of a lunar pattern in the northern mummichog Fundulus heteroclitus macrolepidotus

In this study, the natural spawning season of the northern mummichog Fundulus heteroclitus macrolepidotus was examined from May to July in the lower St John River, New Brunswick, Canada (45° N), through measurements of gonado-somatic index ( I _G), liver-somatic index ( I _L) and condition factor ( K ). I _G increased during the prespawning phase (mean ± s.e. 5·49 ± 0·20%), peaked during the spawning phase (14·68 ± 0·51%) and dropped during the regression phase (3·23 ± 0·29%). A single peak of spawning was observed in F. h. macrolepidotus , contrasting with multiple peaks observed in studies south of 41° N in North America. Within the prespawning phase, there were significant differences between sampling dates in female body mass, gonad mass, liver mass and K . On the basis of results from this study, water temperature is believed to be the predominant factor controlling initiation of spawning in F. h. macrolepidotus .     

The influence of previous feeding regime on the compensatory growth response of maturing and immature Arctic charr, Salvelinus alpinus

Alternating periods of food deprivation with those of unlimited provision of food depressed the growth of Arctic charr, Salvelinus alpinus , below that of controls. Fish that were deprived of food and then fed on alternate weeks (1:1) were larger than those that were exposed to periods of 1 5- or 3-week deprivation and feeding (1·5:1·5 or 3:3). On receiving excess food supplies following 24 weeks on the restricted feeding regimes the previously-restricted fish grew more rapidly than the controls. The greatest compensatory growth was displayed after the 3:3 regime, followed by the 1·5: 1·5 and then the 1:1 feeding regime. At the termination of the experiment there were no significant differences in body weight between fish fed according to the different regimes during the period that food restriction was imposed. Growth patterns of the immature males and females were similar, but mature males were significantly lighter than the immature fish by the end of the experiment. Both immature and maturing fish displayed a compensatory growth response on return to adequate feeding. Beginning food restriction in May did not influence the proportions of male fish ( c . 60%) which were mature in the autumn.