The influence of flood regime on fish catch and fish communities of the Cross River floodplain ecosystem,Nigeria

Synopsis The morphology, climate and flood regime of the Cross River floodplain are summarized and related to the catch, species distribution and abundance of the economically important fishes of the floodplain ecosystem. Two flood indices, FI-1 and FI-2, are used to assess, statistically. the relationship between fish catch and flood regime. There are good positive correlations between the catch (C_T) of year T and the flood index 1 of 1 year T-1 and between (C_T) and the sum of the flood indices 1 and 2 of year T-1 (r = 0.6516 and 0.6894, respectively, both at P = 0.05). Cross River is a relatively highly productive system (in terms of fish catch) and this productivity is attributable mainly to the yearly flooding of the plain when fish find allochthonous food materials in the expanded habitat. Changes in hydrometeorological conditions, such as the drought that affected the northern part of the Cross River basin in 1983–1984. if they persist can effectively reduce fish catch from the system.     

The fish species composition and variation of catch from the small-scale gillnet fishery before, during and after the 1997-1998 ENSO event, central Mexican Pacific

In the tropical and subtropical coastal zone, were highly diverse fish communities occur, it is important to study the small scale fisheries exploiting these communities. For this study, 219 fishing days were carried out in Bahia de Navidad, Jalisco, Mexico. Four gillnets with different mesh sizes (76.2, 88.9, 101.6 and 114.3 mm) were used for the fishing operations, from April 1994 to March 1995 and from January 1998 to December 2000. A total of 26126 organisms weighting 11680 kg were caught. One hundred and eighty three species belonging to 57 families and 19 orders were identified. Ten species accumulated more than 60% of the total abundance and biomass, the remaining species (173) individually contributed with less than 2% of the total abundance and biomass. The most important species in the catch were Microlepidotus brevipinnis, Caranx caballus, Haemulon flaviguttatum, Scomberomorus sierra, C. caninus, C. sexfjasciatus, Lutjanus guttatus and L. argentiventris. The catch per unit of effort showed a large variation during the study, both in number and biomass. On average, 110 fishes and 48.5 kg fishing day(-1) were caught. The maximum values were recorded during January and October 1998 (250 fishes and 100 kg fishing day(-1)), and the minimum values were recorded during September and November 1994 (25 org. and 10 kg fishing day(-1)). The total abundance and biomass was lower during the 1994-95 period (F=6.16, 8.32, P<0.05). There were statistically significant differences among the annual catch from each gillnet. All the environmental changes caused by the ENSO event had ecological and economic effects that can be rated from moderate to severe.     

A comparison of flooded forest and floating meadow fish assemblages in an upper Amazon floodplain

Matched sets of gillnets of different mesh-sizes were used to evaluate the degree to which contiguous and connected flooded forest and floating meadow habitats are characterized by distinct fish faunas during the flooding season in the Peruvian Amazon. For fishes between 38–740 mm standard length ( L _S) (the size range captured by the gear), an overriding pattern of faunal similarity emerged between these two habitats. The mean species richness, diversity, abundance, fish mass, mean and maximum L _S, and maximum mass did not differ significantly between flooded forest and floating meadows. Species abundances followed a log-normal distribution in which three species accounted for 60–70% of the total abundance in each habitat. Despite these similarities, multivariate analyses demonstrated subtle differences in species composition between flooded forest and adjacent floating macrophytes. In addition, the absolute number of species was higher in flooded forest, reflecting a higher percentage of rare species. The day–night species turnover was found to be greater in flooded forests than floating meadows. Further, nocturnal samples had higher abundances and greater species richness than diurnal samples in both habitats. Differences in habitat structural complexity between flooded forest and floating meadows may result in a higher abundance and species richness of day-active species in floating meadows.     

A fish and tetrapod fauna from Romer's Gap preserved in Scottish Tournaisian floodplain deposits

The end‐Devonian mass extinction has been framed as a turning point in vertebrate evolution, enabling the radiation of tetrapods, chondrichthyans and actinopterygians. Until very recently ‘Romer's Gap’ rendered the Early Carboniferous a black box standing between the Devonian and the later Carboniferous, but now new Tournaisian localities are filling this interval. Recent work has recovered unexpected tetrapod and lungfish diversity. However, the composition of Tournaisian faunas remains poorly understood. Here we report on a Tournaisian vertebrate fauna from a well‐characterized, narrow stratigraphic interval from the Ballagan Formation exposed at Burnmouth, Scotland. Microfossils suggest brackish conditions and the sedimentology indicates a low‐energy debris flow on a vegetated floodplain. A range of vertebrate bone sizes are preserved. Rhizodonts are represented by the most material, which can be assigned to two taxa. Lungfish are represented by several species, almost all of which are currently endemic to the Ballagan Formation. There are two named tetrapods, Aytonerpeton and Diploradus, with at least two others also represented. Gyracanths, holocephalans, and actinopterygian fishes are represented by rarer fossils. This material compares well with vertebrate fossils from other Ballagan deposits. Faunal similarity analysis using an updated dataset of Devonian–Carboniferous (Givetian–Serpukhovian) sites corroborates a persistent Devonian/Carboniferous split. Separation of the data into marine and non‐marine partitions indicates more Devonian–Carboniferous faunal continuity in non‐marine settings compared to marine settings. These results agree with the latest fossil discoveries and suggest that the Devonian–Carboniferous transition proceeded differently in different environments and among different taxonomic groups.     

Stream–floodplain connectivity and fish assemblage diversity in the Champlain Valley, Vermont, U.S.A.

To evaluate the influence of main channel–floodplain connectivity on fish assemblage diversity in floodplains associated with streams and small rivers, fish assemblages and habitat characteristics were surveyed at 24 stream reaches in the Champlain Valley of Vermont, U.S.A. Fish assemblages differed markedly between the main channel and the floodplain. Fish assemblage diversity was greatest at reaches that exhibited high floodplain connectivity. Whereas certain species inhabited only main channels or floodplains, others utilized both main channel and floodplain habitats. Both floodplain fish α-diversity and γ-diversity of the entire stream corridor were positively correlated with connectivity between the main channel and its floodplain. Consistent with these results, species turnover (as measured by β-diversity) was negatively correlated with floodplain connectivity. Floodplains with waterbodies characterized by a wide range of water depths and turbidity levels exhibited high fish diversity. The results suggest that by separating rivers from their floodplains, incision and subsequent channel widening will have detrimental effects on multiple aspects of fish assemblage diversity across the stream–floodplain ecosystem.     

Length–Weight relationships of 23 fish species from floodplain ecosystems of the Andean Amazon piedmont,Peru

Length–weight relationships (LWRs) for 23 freshwater fish species from the Andean Amazon piedmont in Peru are presented in this study. Fishes were captured between 2009 and 2010 on lagoons from three basins; Amazonas (Ampiyacu and Apayacu) and Ucayali (Pachitea) using gillnets. In this study, new LWRs are reported for 20 species of 23 species analyzed. The study provides new information on less‐studied species and can serve as a basis for management of fisheries and conservation of this area.     

Diel variation in food intake and diet composition of three native fish species in floodplain lagoons of the Macintyre River,Australia

The feeding periodicity of three species of fishes in floodplain lagoons of the Macintyre River varied during 24 h cycles, however, peak feeding activity (around midday and late afternoon) was similar among the species studied, despite differences in their trophic position. In contrast, sampling season and site seemed to have a stronger effect on the composition of the diet than time of day. These findings have implications for studies of trophic dynamics and food web structure in floodplain lagoons.     

Abundance – distribution relationships in fish assembly of the Amazonas floodplain lakes

This study shows that patterns in some community assemblages are not mainly governed by local factors but also by regional ones. Using field data from 36 floodplain forest lakes in the Amazon basin, we present transect count data on the richness, abundance and distribution of floodplain lake fish species. A total of 194 fish species were collected, of which 43 were classified as short-distance migrants. A positive relation was found for local migratory and sedentary species abundances with distribution at a regional scale. The study also suggests that the probability of the presence of a migratory species is more affected by aspects of river-lake connectivity than sedentary species. Our results seem to indicate that migratory species play an important role in local dynamics of floodplain lakes.     

Dietary–morphological relationships in a fish assemblage of the Bolivian Amazonian floodplain

Morphological correlates of diet were examined in 48 species of freshwater fishes from floodplain lakes in the central part of the Mamoré River (Bolivian Amazon). The species were classified, according to the percentage occurrence of seven food items, into eight broad trophic categories: mud feeders, algivores, herbivores, terrestrial invertivores and omnivores, carnivores, zooplanktivores, aquatic invertivores and piscivores. There were significant relationships between the diet and morphology of the fishes even when the effect of taxonomical relatedness between species was eliminated. Relative gut length was the main morphological variable used to order species on a carnivore to mud feeder gradient. Standard length and head and mouth size were the morphological variables most closely associated with prey size. Mud feeder, algivore and piscivore species appeared as the most dietary and morphologically specialized. These results support both the hypotheses that species morphology influences the diet and that morphological similarity is conserved even in comparison with taxonomically unrelated species.     

Comparing the fish assemblages and food‐web structures of large floodplain rivers

相似文献   

Distribution of endosulfan in water, sediment and fish from Warri river, Niger delta, Nigeria

This article presents the first attempt to quantify the levels and distribution pattern of endosulfan, an organochlorine pesticide in surface water, sediment and fish ( Chrysichthys furcatus and Tilapia zilli ). The samples were collected from three stations (Ovwian, Ekakpamre and Ovu) of Warri River in the western Niger Delta of Nigeria in 2006 during the dry and wet seasons (January–August). A total of 96 samples made up of 24 samples each for water, sediment and fish were analysed in this study. The pesticide levels were analysed using high performance liquid chromatography (HPLC model CECIL 1010) to elucidate its distribution in various environmental compartments. The ranges of concentrations of the pesticide in the matrices were: 0.01–9.23 μg/l (water), 0.06–11.98 μg/gdw (sediment), 0.01–15.06 μg/gdw ( Chrysichthys furcatus) and 0.01–1.80 μg/gdw ( Tilapia zilli ). From this result, decreasing order of occurrence of the pesticide is as follows: fish > sediment > water. The concentrations observed in fish ( Chrysichthys furcatus ) were higher than the levels observed in sediment and water suggesting bioaccumulation of the pesticide by the fish. Spatial variations occurred with downstream stations having statistically higher concentrations in all matrices at P  < 0.05. Seasonal variations occurred with higher concentrations in dry season for water and sediment only, while the fish species had higher concentrations in the wet season. The observed values of endosulfan were above the ecological bench marks (0.02 μg/l) recommended by Nigeria Environmental Protection Agency and European Union. They were also relatively higher than those in previous studies on the Nigerian environment, an observation that calls for regular monitoring of the Niger Delta water bodies.     

Relationships between fish assemblages, macrophytes and environmental gradients in the Amazon River floodplain

During the flood season of 1992–1993, 139 species of fishes were collected from a floodplain lake system in the central Amazon Basin. Fish species distribution was examined relative to abiotic variables in seven vegetation strata on Marchantaria Island, Solimões River. Both environmental variables and species distributions were influenced by a river channel to floodplain-interior gradient. Species diversity was significantly higher in vegetated areas than in unvegetated areas, with deeper water Paspalum repens stands harbouring the highest diversity. As a result, species richness and catches were positively related to habitat complexity, while catch was also negatively related to dissolved oxygen (DO) and water depth. Low DO and shallow waters appeared to act as a refuge from predation. Fish assemblages were related to water chemistry, but species richness was not. Canonical correspondence analysis provided evidence that floodplain fish assemblages formed by the 76 most common species were influenced by physical variables, macrophyte coverage and habitat complexity, which jointly accounted for 67% of the variance of fish species assemblages. Omnivores showed no pattern relative to the river channel to floodplain-interior gradient while detritivores were more likely to be found at interior floodplain sites and piscivores closer to the river. Piscivores could be further separated into three groups, one with seven species associated with free-floating macrophytes in deep water, a second with five species found in shallow waters with rooted grasses and a third with six open water orientated species. The results suggest that fish assemblages in the Amazon floodplain are not random associations of species.     

The food habits of four small-sized species of Mormyridae from the floodplain pools of the Sokoto-Rima river basin, Nigeria

The diet of four species of the family Mormyridae, commonly found in the floodplain pools of the Sokoto-Rima river basin, Nigeria, is described. All four species are small-sized and show a degree of food overlap. Evidence is presented, however, that resource partitioning occurs enabling co-existence of the species in a habitat where food resources become increasingly limited after the cessation of the rains.     

Habitat rehabilitation for juvenile fish in urban waterways: A case study from Berlin,Germany

This study examines the improvement of juvenile fish recruitment by technical rehabilitation measures implemented in two urban waterways in Berlin, Germany: the River Spree and the Teltow Canal. Rehabilitation sites provide new littoral habitats protected from navigation‐induced flow and wake wash and are intended to improve habitat quality for juvenile fish and to support urban fish diversity. Both sites and four control sites with common embankments have been sampled monthly by point electric fishing (875 dips in total) from May to September 2009. In total, 6,243 fish were caught representing 12 species. Two of the species, roach (Rutilus rutilus) and perch (Perca fluviatilis), dominated the fish community, comprising 81.5% and 16.1% of the total catch. Nine species were rare, with relative abundances <1%, which hampered more detailed species‐specific analyses. Of the dips 33% contained no fish, causing zero‐inflation of the dataset. A hurdle regression model confirmed positive effects of reduced hydraulic disturbances and resulting vegetation cover on juvenile fish occurrence. However, it also showed low oxygen concentrations limiting habitat quality, as observed at the older, densely vegetated rehabilitation site in the River Spree. The general improvement of the juvenile fish assemblage by the rehabilitation measure appeared rather low, as partially vegetated, rectangle trapeze and trapeze profile banks had even higher fish abundance. The study also revealed a need for adaptive maintenance to improve the long‐term performance of this type of rehabilitation structure. With the recovery of aquatic vegetation, the technical bank protection should be adaptively removed to retain the connectivity with the main channel for a sufficient oxygen supply for the long‐term functionality as a fish habitat.     

Habitat associations of exploited fish species in the Lower Amazon river–floodplain system

1. Modification of floodplain morphology and land use is widely recognized as a major threat to fish communities of river–floodplain systems. We assess habitat associations of major exploited fish species in the Lower Amazon, where modifications are more extensive than in the Central or Upper Amazon. 2. Habitat was characterized in terms of physical environment, vegetation cover, distance from river and mean depth. Habitat associations of late juvenile and adult fish of the 14 major exploited species were established by comparing the distribution of the habitat sampled with the distribution of the habitat sampled weighed by a fish abundance index (catch per unit of effort). 3. Eight species showed significant habitat associations, generally being most abundant in floodplain lakes. Five of these eight species were associated with open water. Of the three exceptions, two preferred flooded forest lakes and another macrophyte‐dominated channels. The majority of those species with significant associations also preferred waters shallower than 7.25 m and relatively distant from the river mainstream. 4. While flooded forest is often assumed to be a key habitat for Amazon fish, only two of the main exploited species in the Lower Amazon had a significant association with this habitat. The majority of exploited species, including one that is associated with flooded forest in the central and upper Amazon, either showed no habitat associations or preferred open water lakes. The full range of pristine and modified floodplain habitats should be considered as important to fish conservation and fisheries productivity.     

Lake Kainji,Nigeria; A summary of the changes within the fish population since the impoundment of the Niger in 1968

The relative composition of the major fish families in Lake Kainji between 1974 and 1975 is analysed and compared with pre- and post-impoundment data collected by previous workers. Trends in the fishery are assessed, and it is concluded that the cichlids, particularly Sarotherodon (= Tilapia) galilaeus Artedi, are becoming the dominant commercially valuable fish. No evidence was found of a significant recovery in the formerly abundant citharinids.The value of the sampling technique is discussed and criticised in relation to under-assessment of certain species, notably S. galilaeus. The Schilbeidae were found to be one of the most numerous families in the lake but are commercially under-exploited.Department of Zoology, University of Reading     

Opportunistic use of estuarine habitat by juvenile bull trout, <Emphasis Type="Italic">Salvelinus confluentus</Emphasis>, from the Elwha River before,during, and after dam removal

Estuaries are used by anadromous fishes, either as the definitive marine habitat or as transition habitat as they move to fully marine waters, and extent of estuary use may vary with habitat conditions and fish attributes. Bull trout (Salvelinus confluentus) are commonly fluvial or adfluvial, though anadromous populations also exist. However, little is known about estuary use, especially by juveniles of this threatened species. We sampled the estuaries of the Elwha River, where a spawning population exists, and the nearby Salt Creek, where none exists, to reveal seasonal timing of estuarine use by juvenile bull trout, size of those using the estuary, and possible use of the non-natal estuary. We captured juvenile bull trout (all ≥100 mm FL, most <300 mm) in the Elwha River estuary in all months except August, but primarily December through May. None was captured in Salt Creek’s estuary despite comparable sampling effort. We also evaluated how dam removal on the Elwha River influenced bull trout estuarine occupancy by sampling before, during, and after dam removal, because this process enlarged the estuary but also increased turbidity and sediment transport in the lower river. Catches were low before dam removal, increased during and immediately after removal, and returned to low levels in recent years, suggesting that juveniles temporarily sought refuge from conditions associated with dam removal. Our findings indicate juvenile bull trout occupy estuarine habitat opportunistically; this information may aid conservation efforts as anadromous populations occur elsewhere in rivers with estuaries altered by human development.     

Theoretical habitat templets, species traits, and species richness: fish in the Upper Rhône River and its floodplain

• 1 Recent developments in ecological theory concerned with habitat templets, species assemblages, and life history traits were examined for the riverine fish communities of the Upper Rhône River, France, in the context of spatial–temporal habitat variability. Relationships among species traits, habitat utilization of species, the relationship between species traits and habitat utilization, and trends of species traits and species richness in the spatial–temporal variability of the habitat types were analysed.
• 2 Relationships among twelve species traits, and utilization of eight habitats were examined for twenty-five fish species using correspondence analysis; the relationship between species traits and habitat utilization was investigated by co-inertia analysis.
• 3 Positive relationships among species traits were observed for size, fecundity, and the number of reproductive cycles per individual. However, species were not well differentiated according to the habitat utilization, except for habitats rarely connected with the main channel (i.e. two types of oxbow lakes).
• 4 No significant relationship was found between species traits and habitat utilization, nor for either species traits or species richness when examined in the framework of spatial–temporal habitat variability. Only two species traits corresponded (with slight trends) to predictions in a river habitat templet: (i) the number of descendants per reproductive cycle increased along with temporal variability; and (ii) the number of reproductive cycles per individual was either low or high at low temporal variability and intermediate at elevated temporal variability.
• 5 The discrepancy between the predictions of the river habitat templet as well as of the patch dynamics concept and the results observed for the fish in the Upper Rhône was explained in terms of scale problems, the evolutionary ecology of the European fish fauna, and the history of the Rhône River.

     

Ecological fish production in the inland delta of the Middle Danube, a floodplain river

Synopsis Ecological fish production in one parapotamal arm of the Middle Danube inland delta in Slovakia, based on 10 samplings during 5 consecutive years, ranged from 349 to 3272 (bar|x = 1066) kg ha^–1 in total production (P_T) and from 39 to 662 (bar|x = 204) kg ha^–1 in available production (P_A). Young-of-the-year fish made up an estimated 49–62% (bar|x = 54) of the P_T. According to the food production/food consumption budget calculated by three different methods, less than half of the P_T is of autochthonous origin, while most is from other sources. Floodplain fish production includes two components: fish originating within the floodplain and fish that are temporary immigrants. The latter component varies considerably in response to the hydrological regime. To assess the P_T in riverine ecosystems, different seasons and years are needed to give realistic values.This paper is dedicated to my friend and sometime co-worker, Eugene K. Balon, at the occasion of his 65th birthday and transition to University Professor Emeritus. He was one of the first ichthyologists to undertake quantitative studies in large rivers in the late 1950's, when most fish biologists thought that fishes inhabit only the sea, lakes, reservoirs and small streams.