Stability Of Fish Assemblages Research Articles

Seasonality and aquatic metacommunity assemblage in three abandoned gold mining ponds in the southwestern Amazon, Madre de Dios (Peru)

Worldwide demand for gold has caused increased extractive activities in the Western Amazon, resulting in a wide-scale transformation of the Madre de Dios river basin (Peru) due to Artisanal and Small-scale Gold Mining (ASGM). These impactful activities profoundly affect the natural landscape and hydroscape as terra firme forest and floodplain habitats are deforested leaving a vast landscape of abandoned ponds that are subsequently colonized from surrounding water bodies. However, the metacommunity dynamics of these emergent networks of connected wetlands and their environmental drivers remain virtually unknown. Here, we present a one-year (May 2017–May 2018) study conducted to assess the composition, abundance and trophic structure of fish assemblages in three abandoned ASGM ponds and their interactions in relation to those of other freshwater groups (macroinvertebrates, phytoplankton and zooplankton). We aimed to determine the influence of environmental parameters on community composition, focused on flood pulse influence (FPI), seasonality, and to identify indicators for predicting aquatic communities’ assemblages. A remarkably abundance and diversity were found totaling 4601 sampled fish from 6 orders, 27 families, 68 genera and 103 species, as well as 87 macoinvertebrate, 71 phytoplankton and 44 zooplankton taxa. The two FPI ponds showed a more stable fish trophic structure throughout the year than the unique non-FPI, probably due to the floods provision of buffer against the lack of resources that occurs during the dry season. Conversely, fish of higher trophic levels were not detected during the dry and transition-to-wet seasons in the non-FPI pond surveyed. Community trajectory analysis showed greater stability of fish assemblages in the non-FPI pond compared to the FPI ponds, which experienced larger disturbance of environmental parameters and biotic inputs during flooding events. Detrended correspondence analysis showed floods as the key factor influencing aquatic communities and species accumulation. However, whereas floods had a large influence on fish and macroinvertebrates, seasonality was the main driver for plankton. FPI ponds showed six-fold higher fish and macroinvertebrate species richness than non-FPI ones, while plankton showed an opposite trend. FPI was the main factor determining the taxonomic composition of fish, followed by dissolved oxygen. Macroinvertebrates were also affected by FPI together with pH and the presence of grassed banks, while conductivity determined phytoplankton composition. Our study presents novel evidence on the highly heterogeneous communities of ASGM abandoned ponds, highlighting their important ecological value and potential role in providing of ecosystem services currently overlooked from conservation policies and management of the aquatic resources.

Post-Disturbance Stability of Fish Assemblages Measured at Coarse Taxonomic Resolution Masks Change at Finer Scales.

Quantifying changes to coral reef fish assemblages in the wake of cyclonic disturbances is challenging due to spatial variability of damage inherent in such events. Often, fish abundance appears stable at one spatial scale (e.g. reef-wide), but exhibits substantial change at finer scales (e.g. site-specific decline or increase). Taxonomic resolution also plays a role; overall stability at coarse taxonomic levels (e.g. family) may mask species-level turnover. Here we document changes to reef fish communities after severe Tropical Cyclone Ita crossed Lizard Island, Great Barrier Reef. Coral and reef fish surveys were conducted concurrently before and after the cyclone at four levels of exposure to the prevailing weather. Coral cover declined across all exposures except sheltered sites, with the largest decline at exposed sites. There was no significant overall reduction in the total density, biomass and species richness of reef fishes between 2011 and 2015, but individual fish taxa (families and species) changed in complex and unpredictable ways. For example, more families increased in density and biomass than decreased following Cyclone Ita, particularly at exposed sites whilst more fish families declined at lagoon sites even though coral cover did not decline. All sites lost biomass of several damselfish species, and at most sites there was an increase in macroinvertivores and grazers. Overall, these results suggest that the degree of change measured at coarse taxonomic levels masked high species-level turnover, although other potential explanations include that there was no impact of the storm, fish assemblages were impacted but underwent rapid recovery or that there is a time lag before the full impacts become apparent. This study confirms that in high-complexity, high diversity ecosystems such as coral reefs, species level analyses are essential to adequately capture the consequences of disturbance events.

STABILIZING EFFECT OF WWTP DISCHARGE ON WATER QUALITY AND FISH ASSEMBLAGE STRUCTURE. A CASE STUDY

We examined the effluent from a municipal (Ny regyh za, Hungary) wastewater treatment plant (WWTP) on hydrophysicochemical properties and on diversity, community structure, and stability of fish assemblages at the recipient low flow channel system during a two-year period. The WWTP outflow increased significantly the nutrient concentrations (e.g. NO2 and NO3 concentrations increased to 4x and 8x respectively), and the regime (with the permanent ~0.23m3/s load) at the recipient channel sections. The wastewater outflow not only altered, but stabilized the physico-chemical variables measured, and the water regime in the recipient channels. Thus the natural, periodic fluctuation of the environmental variables was diminished in the study period. The WWTP outflow caused significant changes in the fish fauna as well. High abundances and taxa richness were found in the stocks inhabiting the charged watercourse sections. At the same time, species composition and relative abundances of fish stocks proved to be more constant at the impaired sites. Our results show that the WWTP outflow caused altered, but significantly more stable environmental conditions. These alterations were favourable for the emergence of a more diverse and more stable fish community on the recipient channel sections. Hence, the dynamic variability in fish assemblage structure that is characteristic of natural lowland stream was not apparent in these perturbed, semi natural habitats.

The persistence and stability of fish assemblages within eelgrass meadows (Zostera marina) on the Pacific coast of Canada

The persistence and stability of fish assemblages found in 34 eelgrass (Zostera marina) meadows along the British Columbia coast was examined from 2004 to 2011. Assemblage persistence (nontrending species composition) and assemblage stability (constancy in abundance over time) were assessed using a time-lag regression method that tests for temporal turnover within short time series. Overall, 85% of the fish assemblages persisted, and 80% of the assemblages exhibited stability in abundance over the 8-year study. Environmental conditions in 33 of 34 meadows did not change substantially over the 8 years, and the low interannual variability may have contributed to the high persistence and stability of the fish assemblages. The lack of temporal turnover in relatively undisturbed eelgrass fish assemblage properties is a critical element for effective monitoring of coastal ecosystem integrity.

Environmental Variability Affects Distributions of Coastal Fish Species (Maryland)

Abstract We determined how environmental variability affected distributions of seasonally recruiting fishes (i.e., transient species) in coastal lagoons of Maryland from May–October during 1996, 1997, and 1999. A total of 241 monthly sampling events were conducted in the coastal lagoons at 40 sampling stations. Fluctuations in salinity resulting from variation in stream discharge were negatively correlated with intra-annual stability of fish assemblages. Transient, or non-resident species (e.g., recruiting species), were more frequent in habitats where salinity was less variable. When stream discharge lessened during dry years, transient species were more common throughout the coastal lagoons. Thus, environmental variability influenced distributions of young-of-year fishes in coastal estuaries.

The stability of fish assemblages under unstable conditions: A ten-year series from the Polish part of the Vistula Lagoon

Time-series of the species caught in a complex of four fyke nets that were monitored and recorded by a team of volunteer fishers provided the basis for identifying trends in the changes of fish assemblages during the 1995-2006 period. The fish assemblages exhibited strong seasonality with herring, Clupea harengus L. domination during spring. In the summer season, juvenile pikeperch, Sander lucioperca (L.) and ruffe, Gymnocephalus cernuus (L.), were dominant in number. The relative abundance of eel, Anguilla anguilla (L.) exhibited a clearly decreasing trend due to fishery exploitation and the lack of stocking. The decreased share of the largest pikeperch individuals suggested that this species is being overexploited. Ruffe exhibited a strong decline more probably due to strong impact from numerous black cormorants. Increased abundance was observed in the case of roach, Rutilus rutilus (L.), flounder, Platichthys flesus (L.) and round goby, Neogobius melanostomus (Pall.), a new species in ecosystem.

Changes in relative abundance, variability, and stability of fish assemblages of Eastern Lake Ontario and the Bay of Quinte—the value of long-term community sampling

Intensive long-term index sampling of the fish communities of eastern Lake Ontario (outlet basin—gill netting, 1958–98, average annual effort 16.3 km of netting; bottom trawling, 1972–98, 23.0 km; Bay of Quinte—bottom trawling, 1972–98, 12.8 km) provided extensive summer catch data that we used to calculate indices to assess annual relative abundance, variability, and a combination of the two to reflect stability, or status. One of the unique and valuable attributes of these long-term data sets is that they use a community-assessment approach, which includes ecologically important small species and values the data on all species equally. These valuable series confirm that during the past decade, most major species in both the lake and bay have undergone a dramatic, somewhat synchronous change, unprecedented in almost three decades, including the catastrophic winterkills of the late 1970s. Abundance increased to record-high levels in the late 1980s and early 1990s, then decreased abruptly, two years earlier in small species (rainbow smelt, alewife and slimy scalpia) than large ones (lake trout, lake whitefish and walleye). The period of pivotal change was 1991–1993, coinciding with a significant decrease in water temperature from a period of six abnormally warm years, 1986–1991 (Apr.–Sept.—18.7°C), to three abnormally cold years, 1992–1994 (17.3°C). Temperature decrease from 1991 to 1992 (2.1°C) was the most extreme in four decades. Intensive rehabilitative stocking of lake trout, commencing in the mid-1970s, has helped restructure and mature the cold-water community to a point where large species were at record-high levels in the late 1980s and early 1990s, creating increasing prey demand that required maximum prey production; this was possible in the recent high-temperature regime (late 1980s) but was not sustainable in the low-temperature regime that followed. After 1992, large species lost condition, more dead fish were observed, and abundance decreased. This low-temperature perturbation induced a successional setback (enjuvenation event) that should be only temporary in the overall maturity of the ecosystem. However, recent colonization by dreissenids, which are inducing biological oligotrophication, could compound this.

Hypoxic wetland tributaries as faunal refugia from an introduced predator

Abstract– The introduction of Nile perch (Lates niloticus) into the Lake Victoria basin of East Africa has coincided with the decline or disappearance of hundreds of indigenous species. To mitigate additional biodiversity loss, we must learn what limits the spread of Nile perch and what habitats serve as refugia for prey species. Heavily vegetated wetlands may protect fishes from Nile perch predation by providing both structural and low‐oxygen refugia for prey species tolerant of hypoxia. To examine the potential of wetlands as refugia we quantified the composition, persistence, and stability of fish assemblages in a wetland tributary of Lake Nabugabo, a satellite lake of Lake Victoria in which Nile perch have been introduced. Nile perch were extremely rare in the wetland, and nine of the 18 species that have disappeared from the open waters of the satellite lake were captured in the tributary in this study. Dissolved oxygen was chronically low in the river and may be important in shaping fish community characteristics. Faunal attenuation occurred as the dry season progressed and oxygen levels dropped; however, the most common species remained through seasonal changes. The chronically low oxygen conditions in the werland tributary may permit persistence of only hypoxia‐tolerant species. However, wetland conditions seem to limit exploitation by Nile perch providing critical refugia for a subset of the basin fauna.

Changes in relative abundance, variability, and stability of fish assemblages of Eastern Lake Ontario and the Bay of Quinte—the value of long-term community sampling

Abstract Intensive long-term index sampling of the fish communities of eastern Lake Ontario (outlet basin—gill netting, 1958–98, average annual effort 16.3 km of netting; bottom trawling, 1972–98, 23.0 km; Bay of Quinte—bottom trawling, 1972–98, 12.8 km) provided extensive summer catch data that we used to calculate indices to assess annual relative abundance, variability, and a combination of the two to reflect stability, or status. One of the unique and valuable attributes of these long-term data sets is that they use a community-assessment approach, which includes ecologically important small species and values the data on all species equally. These valuable series confirm that during the past decade, most major species in both the lake and bay have undergone a dramatic, somewhat synchronous change, unprecedented in almost three decades, including the catastrophic winterkills of the late 1970s. Abundance increased to record-high levels in the late 1980s and early 1990s, then decreased abruptly, two years earlier in small species (rainbow smelt, alewife and slimy scalpia) than large ones (lake trout, lake whitefish and walleye). The period of pivotal change was 1991–1993, coinciding with a significant decrease in water temperature from a period of six abnormally warm years, 1986–1991 (Apr.–Sept.—18.7°C), to three abnormally cold years, 1992–1994 (17.3°C). Temperature decrease from 1991 to 1992 (2.1°C) was the most extreme in four decades. Intensive rehabilitative stocking of lake trout, commencing in the mid-1970s, has helped restructure and mature the cold-water community to a point where large species were at record-high levels in the late 1980s and early 1990s, creating increasing prey demand that required maximum prey production; this was possible in the recent high-temperature regime (late 1980s) but was not sustainable in the low-temperature regime that followed. After 1992, large species lost condition, more dead fish were observed, and abundance decreased. This low-temperature perturbation induced a successional setback (enjuvenation event) that should be only temporary in the overall maturity of the ecosystem. However, recent colonization by dreissenids, which are inducing biological oligotrophication, could compound this.

Regulation and stability in fish assemblages of neotropical floodplain lakes.

Neotropical floodplain lakes provide an excellent opportunity to examine the regulation and stability of fish assemblages. At low water, when lakes are separated, fish are concentrated in the lakes and are presumably subject to strong interspecific interactions that can shape assemblage structure. At high water, when the lakes and river channels become broadly interconnected, ample potential exists for alteration of assemblage structure because eggs, larvae, and older fish may undergo spatial reshuffling among waterbodies. Twenty lakes of the Orinoco River floodplain in Venezuela were surveyed in the early and late dry seasons of two consecutive years. Marked differences in assemblage structure among lakes were established in the early dry season. Changes in assemblage structure during the dry season were large and detectable even at the ordinal level; they reflected a strong reduction of visually oriented fish relative to fish with adaptations to low light. Changes were similar in the two years and were apparently due to species-specific differences in mortality, which was high over the dry season. The annual flood is a strong natural fluctuation that greatly modifies assemblage properties during the wet season. Nevertheless, the potential for alteration of assemblage structure by reshuffling was not realized: assemblage properties early and late in the dry season were similar in the two years, indicating a regular and predictable annual cycle of change in assemblage structure. This regularity can be explained by mechanisms of regulation which appear to be linked to piscivory and the optical environment. In contrast with the prevailing views on neotropical fish assemblages, there seems to be a strong deterministic component to assemblage structure and dynamics in Orinoco floodplain lakes.

Development and Stability of Fish Assemblages after Lime Treatment

Long-term effects of limestone treatment on fish populations in acidified lakes in Sweden have been examined since 1983 to assess the development and stability of fish assemblages after lime treatment. In total, 77 lakes were sampled twice using standardized methods between 1983 and 1988. The lakes were limed 1–16 yr before the second sampling. Physical and chemical variables and the fish data were reduced using PCA ordination and the resulting relationships were analyzed using linear regression and ANOVA. Relationships between the fish assemblage characteristics and the environmental factors were highly dependent on the species composition of the assemblages. The number and diversity of fish species were correlated with both the extent of acidification and habitat diversity of the lakes. The importance of species interactions after lime treatment was suggested by a negative relationship between changes in the scores of community along the first component of the fish PCA and changes along two of the other species components between the two samplings. Despite a weak tendency towards reduced variability in species proportions as time passed since the first liming, the development of community stability, expressed as lack of change in species proportions, was insignificant.

Stability and Persistence of Fish Faunas and Assemblages in Three Midwestern Streams

Long term stability of summer fish assemblages was examined in three distinct systems: Piney Creek, a medium-sized Ozark upland tributary of the White River, Arkansas; Brier Creek, a small prairie-margin stream, tributary to the Red River, Oklahoma; and the Kiamichi River, a medium-sized river in the Ouachita Uplands draining into the Red River, Oklahoma. Sampling periods and numbers of surveys of the three stream systems were 14 yr and six collections for Piney Creek, 17 yr and five surveys for Brier Creek, and 5 yr and three surveys for the Kiamichi River. The fish faunas of all three streams were persistent (regarding presence-absence of species). In all three streams overall faunal structure was stable, as indicated by similarity indices and by concordance of rank abundance of the common species in each stream across all collection years. The results corroborated a conclusion from earlier work that the total fish fauna is more stable in a more environmentally benign stream (Piney Creek) than in a stream subject to greater environmental extremes (Brier Creek). The fish fauna of the Kiamichi River was also stable across three survey periods with respect to rank order of species abundance. Stability of the fish assemblages at individual locations on all three streams was variable, but four of five locations on Brier Creek, and all five locations on Piney Creek exhibited significant concordance overall in ranks of species abundance. Of 59 possible cases, assemblages at 27 individual locations (=46%) on the three streams showed assemblage stability >0.60 between survey periods. We conclude that at the level of whole-stream faunas, all three of these midwestern streams were stable across the survey years, and that many, but not all, individual locations had relatively stable fish assemblages.