Hydroacoustics for the discovery and quantification of Nassau grouper (Epinephelus striatus) spawning aggregations

Coral Reefs - Fish spawning aggregations (FSAs) are vital life-history events that need to be monitored to determine the health of aggregating populations; this is especially true of the endangered...     

Large mating aggregations and daily long-distance spawning migrations in the bluehead wrasse,Thalassoma bifasciatum

Synopsis The mating system of the labrid fishThalassoma bifasciatum has been extensively described in the literature, and the species has formed the basis for much work in ecology and behavior. However, most work in the past on this species has concentrated in small patch reef habitats. Here I describe a different mating pattern in bluehead wrasses occurring on a large, linear barrier reef in St. Croix, U.S. Virgin Islands. On this reef, very large group-mating aggregations (> 10000 fish) form daily at a single area on the forepart of the reef. Tagging studies showed that fishes are faithful to particular feeding schools arrayed along the forereef, and that they migrate to the spawning grounds along a specific path from distances more than 1.5 km away. No mating appears to occur in other upcurrent areas of the forereef. One-way migration times averaged 52 min from the farthest site studied, and feeding does not occur en route. Despite large differences in time spent in migration, no significant differences existed in fecundity or frequency of spawning among females living at different distances from the mating aggregation. The only apparent differences was a significantlyhigher growth rate in the fishes residing farthest from the aggregation. This higher growth rate corresponded to a higher overall feeding rate in the distant location, suggesting that food intake can more than compensate for the increased costs of migration.     

Evidence for sexual dichromatisms in spawning aggregations of yellowfin grouper Mycteroperca venenosa and tiger grouper Mycteroperca tigris from the southern Gulf of Mexico

Colour pattern characteristics and gonad histology were used to detect sexual dichromatisms in yellowfin grouper Mycteroperca venenosa and tiger grouper Mycteroperca tigris from the Campeche Bank, Mexico. Specimens were obtained from commercial catches between March and May during 2002 and 2004. All specimens were examined dead. Ninety-seven per cent of males had different sex-associated colour patterns. Male yellowfin grouper displayed a bright yellow blotch on both sides of the lower jaw while females retained a reddish lower jaw. Male tiger grouper had uniform dark pectoral fins while females had bright orange pectoral fins. In situ observations of live fishes at fishing sites showed the lower jaw and pectoral fin colourations to be clearly visible underwater at a depth of 35 m. All males of both species and most females (80% yellowfin grouper and 98% tiger grouper) were sexually active and probably caught during their spawning season. This suggests that distinct colourations observed for male M. venenosa and M. tigris may be seasonal displays associated with spawning. Both the lower jaw and pectoral fin colourations were still visible in dead fishes after several days on ice. Differences observed for ray length of exserted vertical fins in tiger grouper specimens were probably not a sex-associated characteristic.     

Patagonian grouper Acanthistius patachonicus (Jenyns, 1840) forms massive spawning aggregations in the Southwest Atlantic

Here we describe massive spawning aggregations and seasonal changes in the large-scale distribution of the Patagonian grouper Acanthistius patachonicus in the Southwest Atlantic based on three sources of information: (a) data from bottom trawl research surveys covering the distributional range of the species within the Argentine continental shelf; (b) folk ecological knowledge gathered from experienced captains of the Argentine industrial trawl fisheries; and (c) sampling of an artisanal trap fishery targeting the Patagonian grouper in a specific location off the coast of Buenos Aires Province. The trawl surveys showed a general pattern of aggregation of Patagonian grouper towards the coast during the reproductive period (September–December). Captains described massive aggregations of the species at specific near-shore locations, where trawl catches of up to 15 t in a single haul were registered during the reproductive season. At a local scale, the artisanal trap fishery described operates exclusively during the reproductive period, targeting near-shore aggregations with a high proportion of individuals releasing gametes onboard. These three sources of information provide evidence of the existence of massive transient spawning aggregations of Patagonian grouper in the Argentine shelf. This is the first report of a reef fish spawning aggregation in the southern region of the Southwest Atlantic. Anecdotal information gathered in this study points to the depletion of many of the aggregations targeted during the 1980s and 1990s by the industrial fleet. At the same time, the spawning aggregation site off Buenos Aires Province has been productive for the last 34 years, being exploited exclusively by traps. The Patagonian grouper is classified as Data Deficient by the International Union for Conservation of Nature, which highlights the need for further research to determine its stock status. Mapping its current spawning aggregations should be a priority to inform the design of a targeted monitoring program and management plan for this species.     

Androgens stimulate sex change in protogynous grouper,Epinephelus coioides: spawning performance in sex-changed males

We examined the efficacy of androgens (1.0 mg/kg body mass), testosterone (T), 11-ketotestosterone (11-KT), 17alpha-methyltestosterone (MT), testosterone propionate (TP) or androgen mixture (T, MT and TP in an equal ratio), for induction of sex change in protogynous orange-spotted grouper, Epinephelus coioides. The spawning performance in sex-changed males was also investigated. MT and androgen mixture at a dose of 1.0 mg/kg BW induced a sex transition and completion of spermatogenesis up to the functional male phase. The androgen mixture was most effective. Significantly, higher plasma T levels were found in MT and androgen mixture groups compared to control and other androgen implantation (T, TP or 11-KT) groups. We found that plasma levels of estradiol-17beta (E2) or 11-KT were not different among treated groups. Sex-changed males could successfully fertilize mature eggs. Fertilization and hatching rates were of 23.5-70.4% and 8.4-44.6%, respectively. The data demonstrated that induction of sex change by exogenous androgens in groups could apply to the aquaculture field for seed production.     

Assortative mating and within-spouse pair comparisons

Spousal comparisons have been proposed as a design that can both reduce confounding and estimate effects of the shared adulthood environment. However, assortative mating, the process by which individuals select phenotypically (dis)similar mates, could distort associations when comparing spouses. We evaluated the use of spousal comparisons, as in the within-spouse pair (WSP) model, for aetiological research such as genetic association studies. We demonstrated that the WSP model can reduce confounding but may be susceptible to collider bias arising from conditioning on assorted spouse pairs. Analyses using UK Biobank spouse pairs found that WSP genetic association estimates were smaller than estimates from random pairs for height, educational attainment, and BMI variants. Within-sibling pair estimates, robust to demographic and parental effects, were also smaller than random pair estimates for height and educational attainment, but not for BMI. WSP models, like other within-family models, may reduce confounding from demographic factors in genetic association estimates, and so could be useful for triangulating evidence across study designs to assess the robustness of findings. However, WSP estimates should be interpreted with caution due to potential collider bias.     

Copulation, spawning and parental care in captive ocean pout

The ocean pout copulates through direct genital contact for internal fertilization. A complete spawning event consists of copulation, oviposition, and the female displaying parental care by wiping and wrapping herself around the eggs.     

Methoprene modulates the effect of diet on male melon fly,Bactrocera cucurbitae,performance at mating aggregations

The effect of access to dietary protein (P) (hydrolyzed yeast) and/or treatment with a juvenile hormone analogue, methoprene (M), (in addition to sugar and water) on male aggregation (lekking) behaviour and mating success was studied in a laboratory strain of the melon fly, Bactrocera cucurbitae (Coquillett) (Diptera: Tephritidae). Six‐day‐old males were treated with (1) protein and methoprene (M+P+), (2) only protein (M?P+), or (3) only methoprene (M+P?), and compared with 14‐day‐old sexually mature untreated males (M?P?). The lekking behaviour of the four groups of males when competing for virgin sexually mature females (14 –16 days old) was observed in field cages. The following parameters were measured at male aggregations: lek initiation, lek participation, males calling, male–male interaction, female acceptance index, and mating success. For all these parameters, the M+P+ males significantly outperformed the other males. Moreover, for all parameters, there was a similar trend with M+P+ > M?P+ > M?P? > M+P?. More M+P+ males called and initiated and participated in lek activities than all other types of male, which resulted in higher mating success. They had also fewer unsuccessful copulation attempts than their counterparts. Whereas treatment with methoprene alone had a negative effect in young males with only access to sugar, access to dietary protein alone significantly improved young male sexual performance; moreover, the provision of methoprene together with protein had a synergistic effect, improving further male performance at leks. The results are of great relevance for enhancing the application of the sterile insect technique (SIT) against this pest species. The fact that access to dietary protein and treatment of sterile males with methoprene improves mating success means that SIT cost‐effectiveness is increased, as more released males survive to sexual maturity.     

Male reproductive competition in spawning aggregations of cod (Gadus morhua, L.)

Reproductive competition may lead to a large skew in reproductive success among individuals. Very few studies have analysed the paternity contribution of individual males in spawning aggregations of fish species with huge census population sizes. We quantified the variance in male reproductive success in spawning aggregations of cod under experimental conditions over an entire spawning season. Male reproductive success was estimated by microsatellite-based parentage analysis of offspring produced in six separate groups of spawning cod. In total, 1340 offspring and 102 spawnings distributed across a spawning season were analysed. Our results show that multiple males contributed sperm to most spawnings but that paternity frequencies were highly skewed among males, with larger males on average siring higher proportions of offspring. It was further indicated that male reproductive success was dependent on the magnitude of the size difference between a female and a male. We discuss our results in relation to the cod mating system. Finally, we suggest that the highly skewed distribution of paternity success observed in cod may be a factor contributing to the low effective population size/census population size ratios observed in many marine organisms.     

Influence of dry diets on reproductive performance and egg lipid composition during the first spawning season of captive pollack

Four‐year‐old pollack Pollachius pollachius L., previously fed on dry pellets since their juvenile stage, were divided into three experimental groups two months prior their first spawning season. They were fed a commercial broodstock pellet enriched with 6% added oils, either: (1) capelin oil (control), (2) capelin oil plus arachidonic acid, or (3) DHA rich tuna oil. Spawning performance was determined in each group and egg lipids were analysed. During the vitellogenic period, the estradiol levels in plasma increased with oocyte enlargement, indicating that captivity and pelleted feed did not affect reproductive capacity. Females from each group spawned spontaneously between February and May. Egg production per kg of female was highest in the control group. Fertilization rate was highest (39%) in the group fed on diet enhanced in DHA. Lipid content in eggs reached 16% of dry mass, containing mainly phospholipids (75%). Egg fatty acid profiles showed few differences between dietary treatments. There was no significant difference in the concentration of Docosahexaenoic acid (22:6n − 3) between groups. Arachidonic acid (20:4n − 6) was lower in neutral and polar lipids of eggs from the control group than in the other groups. Tuna oil diet induced the highest DHA/EPA ratio in eggs and seemed to provide sufficient arachidonic acid for pollack broodstock. Egg fatty acid profiles are compared with 6 year‐old pollack broodstock fed on fish, and with other cultured and wild fish species.     

Temporal variation in male traits, nesting aggregations and mating success in the peacock blenny

At the beginning of the breeding season male Salaria pavo that have eggs in their nests are larger, have more developed anal glands and less intense eye-spots and are located in breeding aggregations. These differences cease to occur from the peak of the breeding season (June—July) onwards. Two scenarios are presented that may explain these results: (1) smaller and younger males may begin to breed later devoting part of the warm season to growth; (2) females may cease to be selective as the nesting space begins to be saturated with eggs. These results raise one methodological and one conceptual question. The search for correlates of male reproductive success must cover different phases of the breeding season to capture the overall dynamics of the processes involved. The operational sex ratio for cavity-spawning fishes should take into account the availability of spawning sites rather than just counting the sexually mature members of each sex.     

Reproductive strategy,spawning induction,spawning temperatures and early life history of captive sicklefin chub Macrhybopsis meeki

Macrhybopsis reproduction and propagule traits were studied in the laboratory using two temperature regimes and three hormone treatments to determine which methods produced the most spawns. Only sicklefin chub Macrhybopsis meeki spawned successfully although sturgeon chub Macrhybopsis gelida released unfertilized eggs. All temperature and hormone treatments produced M. meeki spawns, but two treatments had similar success rates at 44 and 43%, consisting of a constant daily temperature with no hormone added, or daily temperature fluctuations with hormone added to the water. Spawns consisted of multiple successful demersal circular swimming spawning embraces interspersed with circular swims without embraces. The most spawns observed for one female was four and on average, 327 eggs were collected after each spawn. The water‐hardened eggs were semi‐buoyant and non‐adhesive, the first confirmation of this type of reproductive guild in the Missouri River Macrhybopsis sp. From spawn, larvae swam vertically until 123 accumulated degree days (° D) and 167° D for consumption of first food. Using average water speed and laboratory development time, the predicted drift distance for eggs and larvae could be 468–592 km in the lower Missouri River. Results from this study determined the reproductive biology and early life history of Macrhybopsis spp. and provided insight into their population dynamics in the Missouri River.     

Accounting for mating pair formation in plasmid population dynamics

Plasmids are important vehicles for horizontal gene transfer and rapid adaptation in bacteria, including the spread of antibiotic resistance genes. Conjugative transfer of a plasmid from a plasmid-bearing to a plasmid-free bacterial cell requires contact and attachment of the cells followed by plasmid DNA transfer prior to detachment. We introduce a system of differential equations for plasmid transfer in well-mixed populations that accounts for attachment, DNA transfer, and detachment dynamics. These equations offer advantages over classical mass-action models that combine these three processes into a single “bulk” conjugation rate. By decomposing the process of plasmid transfer into its constituent parts, this new model provides a framework that facilitates meaningful comparisons of plasmid transfer rates in surface and liquid environments. The model also allows one to account for experimental and environmental effects such as mixing intensity. To test the adequacy of the model and further explore the effects of mixing on plasmid transfer, we performed batch culture experiments using three different plasmids and a range of different mixing intensities. The results show that plasmid transfer is optimized at low to moderate shaking speeds and that vigorous shaking negatively affects plasmid transfer. Using reasonable assumptions on attachment and detachment rates, the mathematical model predicts the same behavior.     

The MHC and non-random mating in a captive population of Chinook salmon

Detailed analysis of variation in reproductive success can provide an understanding of the selective pressures that drive the evolution of adaptations. Here, we use experimental spawning channels to assess phenotypic and genotypic correlates of reproductive success in Chinook salmon (Oncorhynchus tshawytscha). Groups of 36 fish in three different sex ratios (1:2, 1:1 and 2:1) were allowed to spawn and the offspring were collected after emergence from the gravel. Microsatellite genetic markers were used to assign parentage of each offspring, and the parents were also typed at the major histocompatibility class IIB locus (MHC). We found that large males, and males with brighter coloration and a more green/blue hue on their lateral integument sired more offspring, albeit only body size and brightness had independent effects. There was no similar relationship between these variables and female reproductive success. Furthermore, there was no effect of sex ratio on the strength or significance of any of the correlations. Females mated non-randomly at the MHC, appearing to select mates that produced offspring with greater genetic diversity as measured by amino-acid divergence. Females mated randomly with respect to male genetic relatedness and males mated randomly with respect to both MHC and genetic relatedness. These results indicate that sexual selection favours increased body size and perhaps integument coloration in males as well as increases genetic diversity at the MHC by female mate choice.     

Individual variation in the growth of captive infant gorillas

Serial anthropometric data were obtained during the first year of life of six nursery-reared infant gorillas in the Columbus (Ohio) Zoo. Two of the infants are likely to be monozygotic twins as determined by DNA analysis. Growth curves were fitted to serial measures of cephalo-thoracic-abdominal length, arm length, leg length, head circumference, upper arm circumference, and weight from each gorilla, to describe individual patterns of variation in skeletal growth and body composition. Growth in skeletal measures tended to be curvilinear to varying degrees over the first year of life. Body composition varied more than skeletal measures throughout the first year as a consequence of individual health status. Individual growth and body composition variations appear to reflect both genetic and environmental influences in this small sample of captive infant gorillas.     

Morphological and meristic differences among spawning aggregations of north-east Atlantic herring, Clupea harengus L.

Univariate and multivariate analyses were performed on seven anatomical characters of Atlantic herring, Clupea harengus , sampled from seven discrete spawning grounds to the west of the British Isles and from spawning sites in the Baltic and Thames Estuary. Analysis of mean similarities, Mahalanobis D², percentage overlap and projections from prinicipal co-ordinate analysis demonstrated that a high degree of anatomical similarity exists among the herring spawning communities to the west of the British Isles. Although local aggregations had distinct centres of abundance they appeared to have large overlapping distributions. However, the Celtic Sea sample was found to be distinctly different from adjacent and neighbouring stocks. The samples of coastal herring from the Thames Estuary and the Baltic Sea showed little overlap with other samples.     

Behavioral and endocrine correlates of reproductive failure in social aggregations of captive wolverines (Gulo gulo)

Sociality in mammals is often viewed as a dichotomy, with sociality contrasted against solitariness. However, variation within these broad categories may have strong effects on individual fitness. For example, reproductive suppression of social subordinates is generally associated with group living, but suppression may also occur in solitary species if the behavioral and physiological processes involved can be modulated by the demographic environment. To investigate whether behavioral and physiological traits that normally are associated with group living might be latent even in a solitary species, we explored the level of sociality and investigated causes and mechanisms of reproductive failure in female wolverines Gulo gulo that experienced a highly aggregated social environment in captivity. Behaviorally, females showed low levels of aggression and intermediate levels of social interactions. Reproductive failure seemed to have been related to low social rank and to have occurred between ovulation and implantation in 13 out of 15 breeding attempts. However, three of eight females observed to mate produced offspring, indicating that no individual female fully managed to monopolize breeding. Reproductive failure was not related to elevated levels of glucocorticoid stress hormones. Rather, elevated glucocorticoid levels during the mating season were associated with successful reproduction. We suggest that social tendencies and physiological mechanisms mediating reproductive suppression may be viewed as reaction norms to the social environment. We further suggest that the social flexibility of solitary carnivores might be greater than is commonly observed, due to ecological constraints that may limit aggregation.     

Male size composition affects male reproductive variance in Atlantic cod Gadus morhua L. spawning aggregations

Estimates of Atlantic cod Gadus morhua reproductive success, determined using experimental spawning groups and genetic paternity assignment of offspring, showed that within-group variance in male size correlated positively with the degree of male mating skew, predicting a decrease in male reproductive skew with decreasing size variation among males under natural conditions.