Blue sucker stock characteristics in the Wabash River, Indiana–Illinois, USA

Abstract  Blue sucker, Cycleptus elongatus (Lesueur), populations have declined because of habitat degradation and overharvest, and little information exists on the population characteristics and stock dynamics of this species. We examined size and age structure, mortality, growth and condition of blue sucker in the Wabash River, Indiana–Illinois, USA. A total of 356 fish collected by electric fishing from June 2003 to April 2006 ranged from 238 to 775 mm total length and 85 to 5288 g wet weight. Age ranged from 3 to 16 years and annual mortality ranged from 22 to 25%. Annual growth was greatest among younger age classes (range 48–141 mm yr⁻¹) and declined after age 6, likely at the onset of reproductive maturity. Variation in the relative condition factor (range 66–141) was heteroscedastic over the size range of fish sampled, perhaps attributable to seasonal differences in reproductive condition among mature fish.     

Ecology of larval blue sucker (Cycleptus elongatus) in the Mississippi River

Abstract –  Ecology of larval blue sucker, Cycleptus elongatus , a North American catostomid that has declined throughout its range, is poorly known because larvae have rarely been sampled. A total of 316 young blue suckers (16.0–39.0 mm total length) was captured over 3 years at 14 off-channel sites in Pool 25, Mississippi River. Blue suckers demonstrated distinct temporal and spatial abundance patterns. Blue suckers were only captured in late May/early June, and were more abundant during a year of little flooding. Abundance was correlated with the distance a site was from the main channel, being highest in island borders and island sloughs in proximity to the channel. Fish guts contained a relatively high biomass of chironomids and zooplankton, suggesting islands were providing suitable feeding opportunities. Because of their proximity to flows, slack waters provided by islands were accessible to blue sucker larvae dispersing from channel spawning areas and facilitated their development into rheophilic juveniles.     

Distribution and growth of blue sucker in a Great Plains river, USA

Abstract  Blue sucker, Cycleptus elongatus (Le Sueur), was sampled in the Kansas River, Kansas, USA to determine how relative abundance varies spatially and growth compares to other populations. Electric fishing was conducted at 36 fixed sites during five time periods from March 2005 to January 2006 to determine seasonal distribution. An additional 302 sites were sampled in summer 2005 to determine distribution throughout the river. A total of 101 blue sucker was collected ranging from 242 to 782 mm total length and 1–16 years old. Higher catch rates were observed in upper river segments and below a low-head dam in lower river segments, and catch rates were higher during November in the upriver sites. Kansas River blue sucker exhibited slower growth rates than other populations in the Great Plains including populations as far north as South Dakota.     

Seasonal use distributions and migrations of blue sucker in the Middle Missouri River

Abstract –  Blue suckers, Cycleptus elongatus , are a highly mobile species speculated to have spring spawning migrations. However, previous studies have not quantified seasonal migrations of blue suckers. Use distributions were calculated at 90% and 50% for three seasons to identify geographic space-use requirements of blue suckers. Mean 90% use distributions (±SE) varied from 8.1 km (±5.3 km) in summer to 78.6 km (±9.9 km) in fall to 174.9 km (±13.1 km) in spring. The great space-use requirements of blue suckers in fall and spring indicate that the species makes substantial upstream migrations in fall and also preceding spawning in spring, then return to a core area postspawning. The broad geographical range occupied by blue suckers throughout their life-history cycle emphasises the need for interjurisdictional management of the species and highlights potential detrimental effects of blocking fish passage.     

Persistence of fish populations in the upper Paraná River: effects of water regulation by dams

Abstract –  River–floodplain systems present intense temporal variations in physical, chemical and biological factors. These variations are closely related to alterations in water levels, which have been attributed to the flood pulse. As several species are strictly related to the flood pulse to fulfil their life cycle, the pulse may be seen as a dispersal mechanism of species onto a floodplain. In this study, we determine how dam construction influenced the persistence of Prochilodus lineatus population, a large migratory fish species from the upper Paraná River floodplain. Data used were collected in two distinct periods, from April 1992 to March 1993 and from January 1999 to December 2001. Fish were collected using seining nets in six (monthly in the first period) and seven (quarterly in the second period) isolated lagoons. The fraction of occupied lagoons was high in the first period (higher than 0.65), when flood was intense. However, in the second period, when the flood pulse did not happen or was short, the fraction of occupied lagoons sharply decreased over time (from 0.85 to 0.22). For the first period, no model fitted to data, but for the second period, a negative linear model (named drought-dependent model) presented good fit ( r ² = 0.97). Therefore, it is possible to infer that long and intense flood pulses are important to maintain the persistence of P. lineatus populations in the floodplain. The artificial control of water levels prompted by dams disrupts this dynamic, reducing persistence to critical levels.     

A case history of whirling disease in a drainage system: Battle Creek drainage of the upper Sacramento River basin, California, USA

Abstract. Whirling disease was diagnosed in steelhead trout, Salmo gairdneri Richardson, during 1985 at Coleman National Fish Hatchery in the Battle Creek drainage of the upper Sacramento River basin, California, USA. Early confirmation of the aetiologic agent, Myxobolus cerebralis Hofer, 1903, was difficult. However, later investigation confirmed the identity of the agent and led to a management decision to destroy the 1985 brood year of steelhead trout at the hatchery. Sentinel fish and collections of feral trout were used to survey Battle Creek watershed to determine the source of infectivity. Feral rainbow trout, Salmo gairdneri Richardson, from South Fork Battle Creek were found to be infected with M. cerebralis and other infected trout were later found at two commercial rainbow trout hatcheries. No reinfection with M. cerebralis has been detected at the Coleman hatchery since ozonation was begun in early 1986.     

The relationship of environmental factors to spatial and temporal variation of fish assemblages in a floodplain river in Texas, USA

Abstract –  Spatial and temporal variation of species–environment relationships were evaluated for shallow-margin and deep-water fish assemblages in the Brazos River, a large floodplain river in Texas, USA. Total variation among the deep-water assemblages (11 species, 86% turnover across gill net samples) was greater than for shallow-margins (38 species, 64% turnover across seine samples). For both shallow-margin and deep-water assemblages, variation was greater among sites than between winter and summer seasons. Shallow-margin assemblage structure was related to depth, velocity and substrate, whereas for deep-water assemblages river discharge, temperature and velocity were important. Season itself accounted for little of the variation among either shallow (6.7%) or deep-water (2.3%) assemblages. Overall temporal patterns of shallow-margin samples appeared to show responses to juvenile recruitment, spates and migration of coastal fishes, whereas for deep-water samples, patterns related to use of reproductive habitats, juvenile recruitment and seasonal activity levels. Brazos River assemblages were less variable overall in comparison with studies along similar length of reach in headwater streams and wadeable rivers. The residual variation in species distribution (54% for shallow-margin and 67% for deepwater) that was not explained by instream variables and season suggests a greater influence of biotic interactions in rivers, particularly those across the spatially dynamic interface of main channel habitats and shallow river margins.     

Reproductive characteristics of Ancherythroculter nigrocauda, an endemic fish in the upper Yangtze River, China

Knowledge on the reproductive biology of fishes is critical for understanding a species’ life history and devising appropriate management strategies. Anthropogenic forces, such as damming and overfishing, threaten fishes endemic to the upper Yangtze River. We conducted a study on the reproductive biology of an endemic species, Ancherythroculter nigrocauda in order to provide information on the life history of this species and to assist in its conservation. From July 2011 to June 2012, a total of 417 fishes were captured via monthly sampling by fishermen in the Longxi River, a tributary in the upper Yangtze River. Although the female-male ratio was 1:1.03, females were predominantly larger in body size. Gonad somatic indices and oocyte diameter distribution showed that the spawning period of A. nigrocauda in the Longxi River ranged from April to August, with the peak in April. Body length at 50 % sexual maturity of A. nigrocauda was estimated to be 125 and 106 mm for females and males, respectively. Absolute fecundity of A. nigrocauda varied between 11,300 and 504,630 eggs, with the mean of 162,377 eggs. In conclusion, A. nigrocauda mature early, spawn once, and are highly fecund, all of which are consistent with an r-selected life history. It is recommended that a moratorium on fishing this species be enacted and the culture of this species be continued.     

怒江上游裸腹叶须鱼的年龄结构与生长特性

以2017年5 6月和910月在怒江上游察瓦龙县至那曲县江段采集的225尾裸腹叶须鱼(Ptychobarbus kaznakovi)为研究对象,对比脊椎骨和微耳石两种鉴定年龄材料,分析其年龄结构与生长特性。结果显示:微耳石判别年龄具有较高的准确性和精确度。裸腹叶须鱼优势体长为101~250 mm,占总样本的78.48%,优势体重为0~150 g,占总样本的91.11%。裸腹叶须鱼种群由1~10龄和13龄11个年龄组组成,优势年龄组为3~5龄,占样本总数的66.22%,其中4龄鱼数量最多,占样本总数的27.56%,高龄鱼较少。体长与体重的拟合关系式为:W=2×10-5 L2.8644(R2=0.9893,n=225),Von Bertalanffy生长方程:L t=699.571-e-0.0615(t+0.842 9),W t=2 816.821-e-0.0615(t+0.842 9)2.8644,生长系数k为0.0615,表明怒江上游裸腹叶须鱼为缓慢生长型鱼类。拟合生长速度方程,生长加速度方程得出年龄生长拐点t i为16.27龄,对应的体长l i为455.36 mm,对应体重w i为823.42 g。     

Relationships among invasive common carp,native fishes and physicochemical characteristics in upper Midwest (USA) lakes

Abstract – Common carp Cyprinus carpio is a widespread invasive species that, in high abundance, can impose numerous deleterious effects in aquatic ecosystems. Common carp increase turbidity and nutrient availability while reducing invertebrate prey resources and aquatic macrophytes, transforming shallow lakes from the clear‐ to turbid‐water state. However, potential effects of common carp on native fish communities have received limited attention. We evaluated the relationships among relative abundances of nine native fishes and common carp for 81 lakes in eastern South Dakota and their associated physicochemical characteristics. Inverse threshold relationships among relative abundances of native fishes and common carp were identified for black bullhead Ameiurus melas, black crappie Pomoxis nigromaculatus, bluegill Lepomis macrochirus, white bass Morone chrysops and northern pike Esox lucius, while marginally significant relationships were detected for largemouth bass Micropterus salmoides and smallmouth bass M. dolomieu. Lakes where common carp relative abundance exceeded 0.6 fish per net night had low abundance of native fishes, whereas lower abundance of common carp resulted in variable abundance of native fishes. Lakes with abundance of common carp surpassing 0.6 fish per net night were also characterised by larger surface areas and watersheds and impaired water quality (higher dissolved solids and chlorophyll a concentrations and lower secchi depth). Our results are consistent with the biotic‐abiotic constraining hypothesis that proposes biotic factors can regulate fish populations regardless of abiotic conditions. Thus, common carp abundance may need to be reduced and sustained below ecological thresholds to improve water quality and increase abundance of native fishes.     

Temperature influence on the fish assemblage structure in a large lowland river, the lower Oder River, Germany

Abstract –  Water temperatures were expected to structure river fish assemblages by promoting: (i) offspring's growth and densities in warm years, (ii) spring spawning fish when temperatures increase early and (iii) improved growth and overwintering condition from elongated vegetation periods. Favourable temperature conditions in their first year should improve growth and survival in consecutive years. In the lower Oder River, Germany, fish have been sampled annually, 0+ in July since 1997, and older fish in November since 1998. This data set was analysed to test the hypotheses mentioned above. The water temperature ranged between −0.4 and 25.1 °C during the study period, resulting in substantial variations of the 29 temperature metrics derived from daily means. Cumulative degree-days until catch, in spring and during March, as well as minimum and mean temperatures in March and spring explained 63% of the variability observed. The mean total length of the most frequent 0+ fish differed significantly between years related to temperature. Increased length growth at higher temperatures was a general tendency. Total length and density of 0+ fish were significantly inversely correlated, but the potential influence of temperature on species densities was not significant. The mean fish densities varied not significantly between years. No indication was found that higher total length in the first year of life resulted in an improved growth in subsequent years.
For future research and management it has to be expected that temperature impacts become increasingly significant in regulated river systems. With decreasing hydrodynamics the significance of temperature effects will increase.     

Feeding patterns in five predatory fishes of the high Paranà River floodplain (PR, Brazil)

Abstract— Between March 1992 and February 1993 five piscivorous fish species, Acestrorhynchus lacustris (Reinhardt, 1874), Hoplias malabaricus (Bloch, 1794), Rhaphiodon vulpinus Agassiz, 1829, Salminus maxillosus , Valenciennes, 1840 and Plagioscion squamosissimus (Heckel, 1840), of the high Paranà River floodplain showed a wide total prey spectrum though only three to four taxa were dominant in their diet. Shrimp, Macrobrachium amazonicum , were also common to the majority of species. Seasonal and spatial variations occurred throughout the study period probably due the availability of prey species. The main resources shared by the predators were also the most abundant in the area, with consumption markedly focused on prey about 5.0 cm long. Detrended correspondence analysis was effective in discriminating two groups of predators species that exploited distinct microhabitats. The predators with the least scores consumed small characids that inhabit mid-water or the littoral region, whereas those with the largest scores consumed prey associated to the bottom.     

Diel and seasonal abundance of fishes in the Platte River, Nebraska, USA

ABSTRACT:   The objective of the present study was to determine diel and seasonal patterns of fluvial fish composition and abundance. Electrofishing grids were used to collect fish in the Platte River at North Bend, Nebraska, USA. Sampling was started at 12.00 h and continued every 3 h for a 24-h period. More species were taken during the day than at night in the spring. In contrast, more species were taken at night than during the day in summer. In the fall, equal numbers of species were caught during the day and night. Comparisons of fish densities showed significant differences among the three seasons. Major taxa were significantly more abundant in spring, but river shiner Notropis blennius and western silvery minnow Hybognathus argyritis were more abundant in the fall. The greater nocturnal abundance of fish in summer and fall than in the spring may be due to changes in the physical and chemical characteristics during the study periods. The significance of seasonal difference in abundance of fish assemblages may indicate a response to changes in available habitats.     

Assessing the green sea urchin (Strongylocentrotus drobachiensis) stock in Maine, USA

The green sea urchin (Strongylocentrotus drobachiensis) fishery is of great importance to Maine’s economy. The fishery took off in the late 1980s as a result of expanding export markets, but has experienced substantial decline in landings since 1992 because of large decreases in urchin stock abundance. Fishery-independent surveys have not been conducted, and no formal stock assessment has been done prior to this study. Using the data collected from the fishery and urchin life history parameters derived from scientific studies, we conducted a formal stock assessment for the urchin stock. A stochastic observation-error length-structured model is used to describe the dynamics of the sea urchin population. A robust Bayesian approach is used for estimating fishery parameters because of concerns of possible outliers in fisheries data and mis-specification of priors. This study shows that the current stock is only 10% of the virgin stock biomass and that the exploitation rate is close to 40% suggesting that a large reduction in exploitation rate is necessary.     

Population structure of the climbing perch,Anabas testudineus,in the lower Mekong River basin

Abstract Genetic variation in the climbing perch Anabas testudineus (Bloch) was investigated by sequencing 1047 base pairs of the mitochondrial ND2 gene. A total of 367 fish samples were collected from the Mekong River. The samples were separated into two genetically differentiated intra‐specific groups, the Laotian and Cambodian group, showing a population structure roughly in accordance with geographical location. Genetic differentiation between groups was confirmed by high pairwise F‐statistic values (0.52–0.98). Molecular clock analysis indicated that both populations were separated approximately 240 000 years ago. Additionally, samples within both groups could be divided into several regional small populations. Their genetic variation might have been supported not only by environmental factors including physical barriers, but also by historical events such as migration routes and/or timing of invasions into the Mekong River. These results could be valuable in identifying management units for the conservation of the species and its resource.     

River rehabilitation in an urban environment: examples from the Mersey Basin,North West England

1. The River Mersey is one of the most polluted and heavily engineered watercourses in Europe. Improvements in water quality have led to the re-establishment of fish populations in parts of the catchment. Further improvements in the water quality of the Mersey Basin are planned. The Environment Agency is building on these water quality improvements by improving the physical structure of watercourses and their corridors as part of catchment-wide community-driven initiatives. 2. Two examples are given. Whittle Brook, a small lowland watercourse, was unusual in that the highly engineered and managed stream ran through an area of landscaped ‘green space’ in a modern housing development. The physical structures of the stream and its riparian zone have been restored as an integral feature of its local landscape. The River Alt is a medium-sized lowland watercourse that has been heavily ‘channelized’ in the past. As part of a community-driven catchment plan called ‘Alt 2000’, a culverted section of the river has been restored to an open river corridor designed to create a range of riparian habitats with associated planting. 3. The paper illustrates a multi-functional approach used in urban river rehabilitation and concludes that the involvement of multi-functional teams with the local community is the key to success. © 1998 John Wiley & Sons, Ltd.     

The influence of hydrology on the recruitment of brown trout in an Alpine river,the Ybbs River,Austria

Abstract – We monitored yearly recruitment (1997–2008) of brown trout (Salmo trutta) in a fourth‐order Austrian Alpine river. The relative proportion of recruits to adult fish varied strongly among years (5.6–66.4%). These proportions were strongly correlated with specific flow patterns. High flows before and during the spawning period were positively correlated with recruitment, whereas high flows during incubation and emergence were negatively correlated with recruitment success. Unsteady flow modelling supported a causal hypothesis for these relationships in demonstrating that discharges > 30 m³·s^?1 resulted in substantial sediment motion (erosion and deposition) in suitable spawning areas within the study stretch.     

Reproductive characteristics of female longnose dace in the Coweeta Creek drainage, North Carolina, USA

Abstract – We examined the reproductive characteristics of 38 female longnose dace ( Rhinichthys cataractae ) from one of the southernmost populations of this species during two sampling periods in 1999 (ES=March 1999, LS=June 1999). Our data indicated that ES fish had not spawned, whereas LS fish had begun spawning. The smallest mature female captured was 56 mm SL (age 1+). Mean potential fecundity differed significantly between ES (mean±1 SD=1832±572 oocytes) and LS (mean±1 SD=775±415 oocytes) specimens. Potential fecundity was positively correlated with both standard length and somatic mass for both ES and LS specimens. Oocyte diameter frequency histograms indicated that ES specimens possessed two modes of oocytes, whereas LS fish contained two or three modes. Female longnose dace appeared to spawn more than once during a reproductive season. Oocyte number varied substantially both among individuals within periods and between periods. The number of Mode II oocytes in ES fish was positively correlated with both length and somatic mass. Female longnose dace appeared potentially capable of spawning 6+ clutches per year. GSI values for longnose dace ranged from a high of 21.4% (LS specimen) to 2.4% (ES specimen). Regression analysis demonstrated that there was no evidence of differential reproductive effort between longnose dace of different size in this population.