Fish Populations In Reservoirs Research Articles

Influence of Electrofishing Boat Operation and Driving Techniques on Reservoir Fish Catches

We compared three methods of boat driving and pedal operation using 600‐s transects: these were the parallel continuous (PC), parallel intermittent (PI), and arc‐intermittent (AI) methods for surveying warmwater fishes in reservoirs. We tested differences in total time and distance per transect, CPUE (fish/h, fish/m), and length frequencies of captured fish among methods. The PC method took the least amount of time, while the AI method took the least amount of distance to complete a transect. The AI method provided slightly higher CPUE (fish/h, fish/m) for Bluegill Lepomis macrochirus and Yellow Bass Morone mississippiensis and higher CPUE (fish/m) for Common Carp Cyprinus carpio, Green Sunfish L. cyanellus, and Largemouth Bass Micropterus salmoides. Each method caught similar size ranges of fish; however, there were slight differences in proportions of sizes for Gizzard Shad Dorosoma cepedianum, Largemouth Bass, and Bluegill. Overall, the AI method performed slightly better for a few species; however, difference in the methods were minor. Any technique should work well for monitoring reservoir fish populations when fish/h is the effort metric.

Hydropower impacts on reservoir fish populations are modified by environmental variation

Global transition towards renewable energy production has increased the demand for new and more flexible hydropower operations. Before management and stakeholders can make informed choices on potential mitigations, it is essential to understand how the hydropower reservoir ecosystems respond to water level regulation (WLR) impacts that are likely modified by the reservoirs' abiotic and biotic characteristics. Yet, most reservoir studies have been case-specific, which hampers large-scale planning, evaluation and mitigation actions across various reservoir ecosystems. Here, we investigated how the effect of the magnitude, frequency and duration of WLR on fish populations varies along environmental gradients. We used biomass, density, size, condition and maturation of brown trout (Salmo trutta L.) in Norwegian hydropower reservoirs as a measure of ecosystem response, and tested for interacting effects of WLR and lake morphometry, climatic conditions and fish community structure. Our results showed that environmental drivers modified the responses of brown trout populations to different WLR patterns. Specifically, brown trout biomass and density increased with WLR magnitude particularly in large and complex-shaped reservoirs, but the positive relationships were only evident in reservoirs with no other fish species. Moreover, increasing WLR frequency was associated with increased brown trout density but decreased condition of individuals within the populations. WLR duration had no significant impacts on brown trout, and the mean weight and maturation length of brown trout showed no significant response to any WLR metrics. Our study demonstrates that local environmental characteristics and the biotic community strongly modify the hydropower-induced WLR impacts on reservoir fishes and ecosystems, and that there are no one-size-fits-all solutions to mitigate environmental impacts. This knowledge is vital for sustainable planning, management and mitigation of hydropower operations that need to meet the increasing worldwide demand for both renewable energy and ecosystem services delivered by freshwaters.

Niveles nutricionales asociados con umbrales de impacto ecológico: Alternativa para estimar los criterios numéricos de nutrientes para los embalses en Puerto Rico

Seis embalses de Puerto Rico se monitorearon durante un periodo de 32 meses con el propósito de establecer relaciones entre el estado nutrlclonal de sus aguas y diferentes umbrales de impacto ecológico. Los embalses seleccionados representan el espectro de productividad prevaleciente en los embalses en la Isla. Las concentraciones medianas de fósforo total (TP) en el epilimnio (1 m) fueron las siguientes: Cerrillos, 10 µg/L; Cidra, 33 µg/L; Guajataca, 10 µg/L; La Plata, 49 µg/L; Patillas, 6 µg/L; y Toa Vaca, 22 µg/L. Igualmente, las concentraciones medianas de nitrógeno total (TN) fueron: Cerrillos, 0.22 mg/L; Cidra, 0.74 mg/L; Guajataca, 0.28 mg/L; La Plata, 0.55 mg/L; Patillas, 0.23 mg/L; y Toa Vaca, 0.34 mg/L. Se observaron fuertes correlaciones positivas entre nutrientes y clorofila a (Chl-a). Se obtuvo un coeficiente de correlación de 0.74 para la relación entre TP y Chl-a, y de 0.66 para la relación entre TN y Chl-a. Aumentos en la biomasa algal (determinada por Chl-a) disminuyeron la penetración de luz en la columna de agua (r= -0.70). Se estableció como umbral biológico indicativo de impacto a los usos designados, una concentración de clorofila a de 24 µg/L, basado en la reducción en penetración de luz a ese nivel de Chl-a y su efecto en la capacidad de los embalses de cumplir con el criterio de vida acuática. Las concentraciones de TP y TN asociadas al umbral de impacto de Chl-a (i.e., 24 µg/L) se establecieron basado en un análisis de punto de cambio de los datos. Los valores resultantes, 0.035 mg/L para TP y 0.43 para TN, se pueden considerar como umbrales nutricionales asociados con impacto. Se incorporó un margen de seguridad utilizando la 5, a percentila menor de la distribución de valores "bootstrap" asociados umbral de impacto de Chl-a (i.e., 24 µg/L) (i.e., p<0.05- prueba unilateral). Los criterios resultantes, 0.026 mg/L para TP y 0.41 mg/L para TN, representan la base propuesta para el establecimiento de estándares nutricionales en embalses de Puerto Rico. Diferencias significativas en la profundidad máxima de cumplimiento con el criterio de vida acuática de USEPA (i.e., 5.0 mg/L) se observaron entre los datos ubicados por encima y por debajo de los criterios numéricos propuestos. Esta diferencia, que puede ser crítica para la sustentabilidad de la población de peces en la isla, evidencia la importancia de mantener el estado nutricional de las aguas en nuestros embalses a niveles bajo los umbrales propuestos. La comunidad zooplanctónica se caracterizó por una mezcla de especies previamente identificadas bajo condiciones ambientales similares en la región Neotropical. Se identificaron sesenta y cinco taxones de zooplancton. Los rotíferos fueron el grupo más diverso con 37 taxones, seguido de los cladóceros con 20 taxones y los copépodos con ocho taxones. La abundancia absoluta de los rotíferos evidenció un incremento con aumentos en diferentes índices de eutroficación. Se utilizó un análisis de curva por segmentos para describir la relación entre los rotíferos del género Brachionus (#ind/L) y el fósforo (lnTP). La relación produjo un cambio de punto a una concentración de 26.58 µg/L de fósforo total, lo cual coincide con el criterio numérico propuesto. Además, se obtuvo un cambio de punto de 1.16 m para la relación entre los rotíferos del género Brachionus (#ind/L) y la profundidad Secchi (m), lo cual se puede considerar como un indicador de impacto adicional en los embalses de la isla.

Spatial structuring within a reservoir fish population: implications for management

Spatial structuring in reservoir fish populations can exist because of environmental gradients, species-specific behaviour, or even localised fishing effort. The present study investigated whether white crappie exhibited evidence of improved population structure where the northern more productive half of a lake is closed to fishing to provide waterfowl hunting opportunities. Population response to angling was modelled for each substock of white crappie (north (protected) and south (unprotected) areas), the entire lake (single-stock model) and by combining simulations of the two independent substock models (additive model). White crappie in the protected area were more abundant, consisting of larger, older individuals, and exhibited a lower total annual mortality rate than in the unprotected area. Population modelling found that fishing mortality rates between 0.1 and 0.3 resulted in sustainable populations (spawning potential ratios (SPR) >0.30). The population in the unprotected area appeared to be more resilient (SPR>0.30) at the higher fishing intensities (0.35–0.55). Considered additively, the whole-lake fishery appeared more resilient than when modelled as a single-panmictic stock. These results provided evidence of spatial structuring in reservoir fish populations, and we recommend model assessments used to guide management decisions should consider those spatial differences in other populations where they exist.

DNA barcoding of freshwater fishes and the development of a quantitative qPCR assay for the species-specific detection and quantification of fish larvae from plankton samples.

The barcoding of mitochondrial cytochrome c oxidase subunit 1 (coI) gene was amplified and sequenced from 16 species of freshwater fishes found in Lake Wivenhoe (south-eastern Queensland, Australia) to support monitoring of reservoir fish populations, ecosystem function and water health. In this study, 630-650 bp sequences of the coI barcoding gene from 100 specimens representing 15 genera, 13 families and two subclasses of fishes allowed 14 of the 16 species to be identified and differentiated. The mean ± s.e. Kimura 2 parameter divergence within and between species was 0.52 ± 0.10 and 23.8 ± 2.20% respectively, indicating that barcodes can be used to discriminate most of the fish species accurately. The two terapontids, Amniataba percoides and Leiopotherapon unicolor, however, shared coI DNA sequences and could not be differentiated using this gene. A barcoding database was established and a qPCR assay was developed using coI sequences to identify and quantify proportional abundances of fish species in ichthyoplankton samples from Lake Wivenhoe. These methods provide a viable alternative to the time-consuming process of manually enumerating and identifying ichthyoplankton samples.

Characterization of genetic variance within and among five populations of Sperata seenghala (Skyes, 1839) revealed by random amplified polymorphic DNA markers

The genetic diversity among five populations (Bhadbada reservoir, Mohinisagar reservoir, Bansagar reservoir, Bargi reservoir and Gandhisagar reservoir) was revealed using random amplified polymorphic DNA markers. 10 random primers screened, 5 primers revealed various banding patterns and yielded 71 total loci as an average of which 39.60 (55.77%) were polymorphic between the population and 86.84% within the population of Sperata seenghala . Population wise the highest genetic polymorphism was obtained in Bhadbada reservoir as 67.61% whereas the lowest was in Gandhisagar reservoir as 49.30%. However, Analysis of Molecular Variance indicated low genetic diversity (H pop = 0.0921 ± 0.1249; I = 0.1584 ± 0.1942) in Bansagar reservoir. Relative genetic differentiation (G ST = 0.3993) and restricted gene flow ( N m = 0.7523) as an average indicated low gene diversity among the fish populations. The un-weighted pair group method with averages (UPGMA) dendrogram showed 05 major clusters, each cluster representing a population. Fish population of Mohinisagar reservoir showed high genetic distance (0.3981) with respective Bargi reservoir population and highest genetic identity (0.8846) reflected between Bansagar and Gandhisagar reservoir. Highest genetic distance between Mohinisagar and Bargi reservoir fish populations shows no significant correlation between genetic and geographical distance of the genotypes collected from different lentic and geographical isolated water bodies. This investigation indicated that lowest genetic diversity existed in different geographic populations of S. seenghala . All the five populations were found to be low in genetic variation, which is useful information for future conservation measures of S. seenghala confined in natural water bodies of Madhya Pradesh.

Impacts of Golden Alga Prymnesium parvum on Fish Populations in Reservoirs of the Upper Colorado River and Brazos River Basins, Texas

AbstractSeveral reservoirs in the upper Colorado River and Brazos River basins in Texas have experienced toxic blooms of golden alga Prymnesium parvum and associated fish kills since 2001. There is a paucity of information, however, regarding the population‐level effects of such kills in large reservoirs, species‐specific resistance to or recovery from kills, or potential differences in the patterns of impacts among basins. We used multiple before–after, control–impact analysis to determine whether repeated golden alga blooms have led to declines in the relative abundance and size structure of fish populations. Sustained declines were noted for 9 of 12 fish species surveyed in the upper Colorado River, whereas only one of eight species was impacted by golden alga in the Brazos River. In the upper Colorado River, White Bass Morone chrysops, White Crappie Pomoxis annularis, Largemouth Bass Micropterus salmoides, Bluegill Lepomis macrochirus, River Carpsucker Carpiodes carpio, Freshwater Drum Aplodinotus grunniens, Channel Catfish Ictalurus punctatus, Flathead Catfish Pylodictis olivaris, and Blue Catfish I. furcatus exhibited sustained declines in relative abundance, size structure, or both; Gizzard Shad Dorosoma cepedianum, Longnose Gar Lepisosteus osseus, and Common Carp Cyprinus carpio did not exhibit those declines. In the Brazos River, only the relative abundance of Blue Catfish was impacted. Overall, toxic golden alga blooms can negatively impact fish populations over the long‐term, but the patterns of impact can vary considerably among river basins and species. In the Brazos River, populations of most fish species appear to be healthy, suggesting a positive angling outlook for this basin. In the upper Colorado River, fish populations have been severely impacted, and angling opportunities have been reduced. Basin‐specific management plans aimed at improving water quality and quantity will likely reduce bloom intensity and allow recovery of fish populations to the abundances and size structures present before golden alga.

Criteria and procedures for evaluating the quality of fish populations in reservoirs

Abstract Routine assessments of sport fish populations are necessary for managers to determine whether populations are meeting objectives. An effective assessment technique should entail rating parameters that are measurements of, or are influenced by the three rate functions of recruitment, growth, and mortality. It will enable managers to determine which rate functions may be preventing a population from achieving stated objectives and help them determine if additional management or research efforts are needed. The first requirement of an effective assessment technique is a standard sampling method that captures all sizes of fish that are present in the population. The sampling method should detect changes in population density and size structure, which will then be reflected in sample length frequencies. Other important criteria are the selection of appropriate parameters from the sample data and the setting of objectives for those parameters. An ideal assessment should include parameters that depict recruitment levels, adult density, growth rate, age structure, and size structure. The parameter value should be easy to calculate from sample data. Use of an assessment for white crappies in Missouri’s large reservoirs showed that growth was generally good, but mortality was high. Subsequent research indicated that angler exploitation was the cause of the high mortality, which led to the successful implementation of restrictive harvest regulations.

Effect of Stream Impoundment in Tennessee on the Fish Populations of Tributary Streams

Data from a statewide survey of warm water streams in Tennessee were used to determine the extent to which gizzard shad (Dorosoma cepedianum), carp (Cyprinus carpio), smallmouth buffalo (Ictiobus bubalus), and drum (Aplodinotus grunniens) inhabit smallmouth bass-rock bass streams. Reproduction of those species in tributary streams was minor or absent. By comparing samples from streams that were accessible from an impoundment and streams that were in an unimpounded watershed, it was shown that large populations of gizzard shad, carp, smallmouth buffalo, and drum in streams originate in impoundments. Mill dams on tributary streams were found to be effective barriers to the upstream movement of fish from the impoundment. Once reservoir fish populations were well established, there appeared to be no consistent variation in the populations of lake fish in tributary streams from one reservoir to another. In streams without migration barriers there was no decrease in the concentration of lake fish with an increase in the distance from an impoundment. Population pressure among fish of the various species in the impoundment is advanced as the reason for movement of gizzard shad, carp, smallmouth buffalo, and drum into streams. It is suggested that mill dams be preserved as barriers to movement of lake fish and that pre-impoundment surveys include consideration of the effect not only on the inundated stream but on the streams above the full-pool level of the proposed reservoir.