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Spawning Sites (spawning + site)
Selected AbstractsSpawning site selection by feral cane toads (Bufo marinus) at an invasion front in tropical AustraliaAUSTRAL ECOLOGY, Issue 5 2006MATTIAS HAGMAN Abstract Spawning sites are a critical and often scarce resource for aquatic-breeding amphibians, including invasive species such as the cane toad (Bufo marinus). If toads select spawning sites based on habitat characteristics, we can potentially manipulate those characteristics to either enhance or reduce their suitability as breeding sites. We surveyed 25 spawning sites used by cane toads, and 25 adjacent unused sites, in an area of tropical Australia recently invaded by these feral anurans. Water chemistry (pH, conductivity, salinity, turbidity) was virtually identical between the two sets of waterbodies, but habitat characteristics were very different. Toads selectively oviposited in shallow pools with gradual rather than steep slopes, and with open (unvegetated) gradually sloping muddy banks. They avoided flowing water, and pools with steep surrounds. In these respects, cane toads broadly resemble previously studied toad species in other parts of the world, as well as conspecifics within their natural range in South America. [source] Population density of migratory and resident brown trout (Salmo trutta) in relation to altitude: evidence for a migration costJOURNAL OF ANIMAL ECOLOGY, Issue 1 2001T. Bohlin Abstract 1For anadromous salmonids, the positive relations found in previous studies between adult size/age and stream characteristics suggest that the migration cost increases with stream length, water discharge and the altitude of the spawning site. In this study we hypothesized that the altitude of the spawning site is positively related to the migration effort. 2Life-history theory predicts (i) that the equlibrium egg density, which is a fitness measure, thereby will decline more rapidly with altitude in migratory than in stream-resident populations, and therefore (ii) that residency will be selected for at large enough altitudes. 3As the density of juveniles is a function of egg density, we hypothesized that (a) altitude has stronger effect on juvenile density in migratory than in resident populations, and (b) juvenile density is larger in migratory than in resident populations. 4We tested (a) and (b) using multivariate methods for electrofishing data from 164 sea-migratory and 167 stream-resident populations of brown trout Salmotrutta L. in Sweden. Both predictions were supported; the juvenile density was larger and declined more rapidly with altitude in migratory than in resident populations. 5The results are further evidence that migration costs reduce fitness in anadromous salmonids. [source] Conservation and management implications of fine-scale genetic structure of Gulf sturgeon in the Pascagoula River, MississippiJOURNAL OF APPLIED ICHTHYOLOGY, Issue 4 2004M. A. Dugo Summary The anadromous Gulf sturgeon occurs along the north central coast of the Gulf of Mexico and is federally listed as threatened. We analyzed fine-scale patterns of Gulf sturgeon population structure, focusing on the Pascagoula River drainage of Mississippi, in reference to movement patterns as determined via telemetry and capture data. We genotyped 361 Gulf sturgeon using eight microsatellite loci including samples from the Pascagoula, Pearl, Escambia, Yellow, Choctawhatchee, and Apalachicola river drainages. Pairwise FST estimates indicated that genetic structure occurs at least at the drainage level. The Pascagoula and Pearl rivers form a western group, demonstrating 100% bootstrap support for a division with drainages to the east. Assignment tests detected non-natal genotypes occurring in all drainages. According to assignment tests, the Pascagoula supports an admixture of individuals, containing minimal influence from drainages to the east (2%) and substantial interaction with the Pearl River (14.1%). The occurrence of Pascagoula River fish in the Pearl was non-reciprocal, observed at 1.1%. After accounting for non-natal genetic diversity within the Pascagoula, there remained a disparity between a pooled Pascagoula group and the only documented spawning site within the drainage located in the Bouie River. We interpret this as an indication of a second genetic stock within the Pascagoula River drainage. Radio telemetry data suggest that spawning likely occurs in the Chickasawhay River, in areas isolated from the Bouie River spawning site by about 350 river kilometers. We emphasize the utility of integrating field and molecular approaches when delineating fine-scale patterns of population structure in anadromous fishes. [source] Endurance swimming of European eelJOURNAL OF FISH BIOLOGY, Issue 2 2004G. Van Den Thillart A long-term swim trial was performed with five female silver eels Anguilla anguilla of 0·8,1·0 kg (c. 80 cm total length, LT) swimming at 0·5 body lengths (BL) s,1, corresponding to the mean swimming speed during spawning migration. The design of the Blazka-type swim tunnel was significantly improved, and for the first time the flow pattern of a swim tunnel for fish was evaluated with the Laser-Doppler method. The velocity profile over three different cross-sections was determined. It was observed that 80% of the water velocity drop-off occurred over a boundary layer of 20 mm. Therefore, swim velocity errors were negligible as the eels always swam outside this layer. The fish were able to swim continuously day and night during a period of 3 months in the swim tunnel through which fresh water at 19° C was passed. The oxygen consumption rates remained stable at 36·9 ± 2·9 mg O2 kg,1 h,1 over the 3 months swimming period for all tested eels. The mean cost of transportation was 28·2 mg O2 kg,1 km,1. From the total energy consumption the calculated decline in fat content was 30%. When extrapolating to 6000 km this would have been 60%, leaving only 40% of the total energy reserves for reproduction after arriving at the spawning site. Therefore low cost of transport combined with high fat content are crucial for the capacity of the eel to cross the Atlantic Ocean and reproduce. [source] Patterns in the spawning of cod (Gadus morhua L.), sole (Solea solea L.) and plaice (Pleuronectes platessa L.) in the Irish Sea as determined by generalized additive modellingFISHERIES OCEANOGRAPHY, Issue 1 2000Eleven ichthyoplankton cruises were undertaken covering most of the Irish Sea during the period February to June, 1995. To identify spawning localities and investigate temporal trends in egg production, the data on stage 1 A egg distributions of cod (Gadus morhua), plaice (Pleuronectes platessa) and sole (Solea solea) have been modelled using generalized additive models (GAMs). A two-stage approach was adopted where presence/absence was firstly modelled as a binary process and a GAM surface subsequently fitted to egg production (conditional on presence). We demonstrate that this approach can be used to model egg production both in space and in time. The spawning sites for cod, plaice and sole in the Irish Sea were defined in terms of the probability of egg occurrence. For cod, we demonstrate that by integrating under predicted egg production surfaces, a cumulative production curve can be generated and used to define percentiles of production and thus delimit the extent of the spawning season. However, for plaice and sole, the surveys did not fully cover the spawning season and the limitations that this imposes on GAM modelling of these data are discussed. Comparison of the spawning sites in 1995 with historical data suggests that the locations of cod, plaice and sole egg production in the Irish Sea have probably remained relatively constant over the last 30 years. [source] Genetic restoration of a stocked brown trout Salmo trutta population using microsatellite DNA analysis of historical and contemporary samplesJOURNAL OF APPLIED ECOLOGY, Issue 4 2006MICHAEL M. HANSEN Summary 1Gene flow from domesticated to wild populations is a major threat to wild salmonid fish. However, few studies have addressed how populations could be restored after admixture has occurred. We analysed the prospects for restoring the previously intensively stocked brown trout population of the Skjern River, Denmark, by identifying remaining non-admixed individuals to be used for supportive breeding. 2We analysed microsatellite DNA markers in historical (1940,50s) and contemporary (1992,2004) samples from the Skjern River system, from the strain of domesticated trout previously used for stocking, and from the neighbouring Storå River. We analysed admixture proportions to estimate the genetic contribution by domesticated trout. We identified non-admixed trout using assignment tests, and further analysed the possible sources of indigenous trout by estimating contemporary migration among populations. 3Genetic differentiation between the historical Storå and Skjern river populations was low (,ST = 0·004), suggesting considerable gene flow in the past. The contemporary Skjern and Storå river populations and a supportive breeding brood stock were strongly admixed, but some non-admixed individuals nevertheless remained in the wild-caught samples. In addition, two resident populations in isolated tributaries were found to be indigenous. The indigenous anadromous individuals from the Skjern River were unlikely to have been recruited from either the isolated tributary populations or the neighbouring Storå River and were presumably derived from unidentified spawning sites in the river system. 4All but one non-admixed anadromous Skjern River trout were females, which we ascribed to sampling bias. Moreover, all non-admixed fish were late-spawning (January,February) whereas the majority of all trout caught for the study were ripe by November,December. The difference in spawning time could be an important factor delaying complete admixture of domesticated and indigenous trout. 5Synthesis and applications. This study demonstrates the feasibility of restoring populations that have been admixed with exogenous individuals, by identifying non-admixed individuals using genetic markers. However, the results also highlight the problem that numbers of identified non-admixed individuals may be small, necessitating identification of nearby, closely related populations that can be incorporated into breeding programmes. [source] Temporal changes in Sander vitreus egg thiamine levelsJOURNAL OF FISH BIOLOGY, Issue 4 2005M. E. Barnes Thiamine pyrophosphate was the predominant form of thiamine present initially in walleye Sander vitreus eggs from two spawning locations in Lake Oahe, South Dakota, U.S.A. Total thiamine content in the eggs at fertilization was 5·18 and 7·97 nmol g,1 for eggs from the Moreau and Grand River spawning sites respectively, and egg thiamine content in all its forms dropped dramatically at the next sampling period of 48 temperature units (TU). Thiamine values did not significantly drop after the 48 TU period, but mean total thiamine composition was < 0·9 nmol g,1 at the last sampling date (156 TU) just prior to hatching. [source] Reproductive migration of brown trout in a small Norwegian river studied by telemetryJOURNAL OF FISH BIOLOGY, Issue 1 2004A. Rustadbakken The movement of 34 large (39,73 cm standard length) brown trout Salmo trutta was monitored using radio telemetry for up to 74 days in Brumunda, a small Norwegian river (mean annual discharge 3·3 m3 s,1) flowing into the large Lake Mjøsa. The maximum range of movement in the river was 20 km. No clear relationships existed between individual movement and water discharge, temperature and barometric pressure. Brown trout migrated at all levels of water discharge. At low discharge (<2 m3 s,1) movements were nocturnal. A weir 5·3 km from the outlet restricted ascending brown trout at low (c. 6° C), but not at high (c. 8° C) water temperatures. Spawning occurred in September to October and tagged individuals spent 2,51 days at the spawning sites. Mean migration speed from tagging to when the fish reached the spawning area, and from when they left the spawning areas and reached the lake was 1·0 and 2·3 km day,1, respectively. All tagged brown trout that survived spawning returned to the lake after spawning. [source] Spawning site selection by feral cane toads (Bufo marinus) at an invasion front in tropical AustraliaAUSTRAL ECOLOGY, Issue 5 2006MATTIAS HAGMAN Abstract Spawning sites are a critical and often scarce resource for aquatic-breeding amphibians, including invasive species such as the cane toad (Bufo marinus). If toads select spawning sites based on habitat characteristics, we can potentially manipulate those characteristics to either enhance or reduce their suitability as breeding sites. We surveyed 25 spawning sites used by cane toads, and 25 adjacent unused sites, in an area of tropical Australia recently invaded by these feral anurans. Water chemistry (pH, conductivity, salinity, turbidity) was virtually identical between the two sets of waterbodies, but habitat characteristics were very different. Toads selectively oviposited in shallow pools with gradual rather than steep slopes, and with open (unvegetated) gradually sloping muddy banks. They avoided flowing water, and pools with steep surrounds. In these respects, cane toads broadly resemble previously studied toad species in other parts of the world, as well as conspecifics within their natural range in South America. [source] | |||||||||||||