Affect Fish Abundance Research Articles

How do natural changes in flow magnitude affect fish abundance and biomass in temperate regions? A systematic review

Abstract We conducted a systematic review on the impacts of natural causes of variation or changes in flow magnitude (resulting from climatic variability and broad‐scale drivers such as climate‐induced change) on fish abundance and biomass in temperate regions. Following our systematic review protocol (Birnie‐Gauvin et al., 2021), we examined commercially published and grey literature originally identified during a recent systematic map process (Rytwinski et al., 2020) and a systematic search update. Articles were screened using an a priori eligibility criteria, with consistency checks performed at the title and abstract, and full text screening stages. All eligible articles were assessed for study validity. A narrative synthesis included all available evidence (300 studies from 219 articles), and meta‐analyses (1863 datasets from 193 studies) were conducted where appropriate. Most studies were conducted in the United States (65%) on genera in the Salmonidae and Leuciscidae families (29% and 28%, respectively), and mainly investigated variation in flow magnitude, followed by droughts and floods. We found that fish abundance and biomass responses to changes in natural flow magnitude were mainly negative, but analyses do not support clear generalizable signals across all contexts (e.g. types of changes in flow magnitude, taxa, locations). When exploring reasons for heterogeneity in effect sizes, we found a detectable effect of intervention type on average fish abundance within the first year of the natural change in flow magnitude, with floods and droughts associated with overall negative responses. However, these patterns were more variable when considering between‐year variation or specific taxonomic responses. Our results suggest that while immediate responses were more apparent and relatively consistent within specific types of natural events, fish populations may recover after such events (i.e. ≥2 years post‐natural event); however, most studies were short in duration (<2 years) and longer‐term effects were more variable and may be context dependent. To improve our understanding of species‐specific and population‐level effects, as well as time‐lags in fish responses to natural changes in flow regimes, standardized, long‐term continuous monitoring both before and after a change in flow magnitude are needed to address knowledge gaps. Studies that focus on systems outside North America are recommended.

Indirect effects of cleaner fish Labroides dimidiatus on fish grazing per reef area and benthic community structure

Grazing fishes farm algae, and consume algae, detritus and sediment and consequently differentially modify benthic communities. Manipulations of cleaner fish Labroides dimidiatus on reefs show that cleaners affect fish abundance differently according to grazer functional group. Accordingly, whether reefs are grazed differently, with consequences for the benthos (fouling material tile−1), was tested using reefs kept free of L. dimidiatus for 10 years compared with undisturbed control reefs. We recorded on video the grazing density (bites tile−1 h−1 reef−1) on settlement tiles and the natural benthos (roving fishes only), according to territorial algal farmer (Pomacentridae) and roving grazer (Acanthuridae, Labridae, Siganidae) functional groups, and measured the accumulation of fouling material tile−1 after 10 months. Grazing density on tiles (dominated by ‘indeterminate’ farmers, and roving ‘sediment-removing’ detritivore Ctenochaetus striatus) and the natural benthos (dominated by Ct. striatus and other grazers) was not measurably affected by cleaner presence. The composition of fouling material (dominated by detritus > turf algae > sediment > other) and organic and inorganic dry weight of material tile−1 were also not measurably affected by cleaner presence. This points to resilience of the benthic community to loss of cleaners. The likely complex interactions between cleaner fish presence, grazer abundance and mobility, and the often-opposite effects of territorial farmers and roving grazers on the benthos underscore the challenge in determining indirect effects of cleaners on benthic community structure. However, a lack of cleaners has negative ramifications for fish populations and physiology and thus their loss remains problematic for client fishes.

PUMMA (Perangkat Ukur Murah untuk Muka Air) performance for water level monitoring of mangrove ecosystem in Pangandaran

PUMMA is a real-time tide gauge that has been operating in several locations in Indonesia. One of them was installed in a mangrove area of Pangandaran that supports both the fisheries and tourism sectors. Tidal dynamics is one of the factors that can affect fish abundance in the mangrove ecosystem. PUMMA Pangandaran monitors the water levels of the mangrove ecosystem in real-time 24/7 and produces CCTV images. This paper aims to analyze the performance of the PUMMA in Pangandaran based on data from water level measurements and image quality from CCTV. The results show that the tidal range in the waters of the mangrove ecosystem in Pangandaran is 1.3 m, with the maximum and minimum high tides being 0.79 m and -0.53 m. The tidal type in the mangrove ecosystem in Pangandaran is semidiurnal and affected by geometry of the estuary. The water level in the mangrove area was influenced by sediments that form a sandbar at the mouth of the Ciputrapinggan River, which controls the fluxes of seawater. There is a data gap of 368 hours during the operation period of PUMMA, and mostly due to technical problems that often occurred at the beginning of the installation. However, after March and April, its performance was improved with only three hours data gap. For the quality of CCTV images, good quality contributed to about 76.67% and only 5.06% on bad quality. Overall, PUMMA’s performance showed excellent reliability in monitoring the water levels and the conditions of the mangrove ecosystem.

How do natural changes in flow magnitude affect fish abundance and diversity in temperate regions? A systematic review protocol

Abstract Natural flow regimes play important roles in maintaining the ecological integrity and diversity of aquatic ecosystems. Wildlife has adapted over time to the natural dynamics of their environment, including changes in flow regimes. Changes in flow, including changes in magnitude, frequency, duration, timing and rate of change, may affect the physical characteristics of aquatic habitats, access to habitats, food availability, population dynamics and community composition. Given the importance of natural flow regimes for fish, it is necessary to understand the extent to which natural flow regimes alter fish abundance and diversity. Here we present a protocol for a systematic review that will estimate how fish abundance and diversity are affected by natural variation (resulting from climatic variability and broad‐scale drivers such as climate‐induced change) in flow. This systematic review will use evidence published before 2016 that was identified in a recent systematic mapping exercise on the broader topic of flow regime change impacts (both natural and anthropogenic) on direct outcomes of freshwater or estuarine fish productivity. An updated English language search will be performed using six bibliographic databases, Google Scholar and networking tools to include commercially published and grey literature that has been published after 2016. Eligibility screening will be conducted at two stages: title and abstract, and full‐text. We will include all studies that evaluate the effect of natural changes in flow magnitude on fish abundance (broadly defined to also capture density and biomass metrics) and species diversity (broadly defined to also capture species richness and composition metrics). Any freshwater or estuarine fish species in temperate regions will be considered. Included eligible studies will be assessed for study validity. We will extract information on study characteristics, intervention/comparator details, measured outcomes and effect modifiers. A narrative synthesis will describe the quantity and characteristics of the available evidence, and where sufficient numbers of similar studies are available, a meta‐analysis will be conducted to estimate an overall mean and variance of effect.

Highly diverse mesophotic reef fish communities in Raja Ampat, West Papua

Mesophotic coral ecosystems (MCEs; reefs 30–150 m depth) are poorly studied, with existing research heavily geographically biased away from the most species-rich reef regions. Yet, MCEs are of high interest because of their unique species and potential to act as refuges from the impacts of fishing. Using baited remote underwater video systems, we surveyed reef fish communities from 2 to 85 m depths throughout the Raja Ampat archipelago in West Papua, Indonesia—an area considered the heart of the Coral Triangle where coral reef biodiversity is greatest. We sought to provide the first assessment of fish communities across this depth gradient in the region and identify whether human population density and market access differently affected fish abundance based on depth. Here we show that—similar to shallow reefs—Raja Ampat MCEs are exceptionally diverse, with 152 fish species recorded at depths greater than 40 m. We found that fish community structures were highly depth driven, with declines in fish abundance at increased depth. In contrast to previous studies elsewhere in the world, we found that the proportion of planktivores declined across the shallow reef to MCE depth gradient. While greater human population density correlated with lower Epinephelidae and Lutjanidae abundance (two key fisheries families), we did not find evidence that MCEs provide a depth refuge from fishing. Surprisingly, we also found that fish abundance declined at greater distances from the major regional market—likely caused by historical fisheries pressure in more remote areas. These results both expand upon and contrast some previously established MCE-depth patterns and human impact patterns on fish communities, suggesting that regional context and historical pressures matters. Our findings highlight the need for future MCE studies within the Coral Triangle region.

Limited effects of Sargassum horneri, an invasive alga, on temperate reef fish assemblages

Biological invasions can dramatically affect the ecology of invaded regions, and globally have resulted in economic damages that total billions of dollars annually. In recent years, an invasive alga, Sargassum horneri, has become established and spread along the coast of southern California (USA). Using field observations and a field experiment, we explored how this non-native alga influences the structure of fish assemblages on temperate reefs in southern California where S. horneri has become prolific. Fish and algal assemblages were quantified along transects on rocky reefs at depths of 3 and 6 m at 6-8 study sites spanning 5 km on 4 occasions over 1.5 yr. Spatiotemporal variation in the fish assemblage was not strongly correlated with the abundance of invasive S. horneri over this period, although it became less variable as native giant kelp Macrocystis pyrifera disappeared from the study sites due to a warm-water event, during which the invasive S. horneri became more dominant. An experiment removing a total of 4.25 t of S. horneri from 6 × 6 m plots (n = 14) revealed that the invasive alga did not affect fish abundance, species richness, species diversity (H’), or multivariate assemblage structure over a 5 mo period. Overall, we found little evidence of negative effects of S. horneri on fishes even though it drastically changed the underwater landscape. Nevertheless, we advise cautionary management actions to limit the movement of this invasive alga because its effects on other community members, such as other algal species, may be detrimental, and longer-term effects on fishes might develop.

Environmental and Anthropogenic Factors Affect Fish Abundance: Relationships Revealed by Automated Cameras Deployed by Fishers

This project was funded by the Australian Commonwealth Government through the Fisheries Research and Development Corporation, Project reference: 2011/021.

Evaluación de la estructura del ensamble de peces de un arrecife costero norpatagónico sometido a diversos impactos antrópicos

Fil: Jeres, Pablo. Universidad Nacional del Comahue. Escuela de Ciencias Marinas; Argentina

The dynamics of coral reef benthic and reef fish communities in Batam and Natuna Islands, Indonesia

ABSTRACTThe dynamics of coral reef benthic and fish communities and their relationship within the Batam and Natuna Islands were investigated in 2004, 2007, 2010 and 2013. Hard coral covers declined at both locations (Batam by 18.69% and Natuna by 16.50%) in 2013, after which a mass bleaching event occurred in 2010. This dramatically affected fish abundance, given that there was a decline of 39.18 individuals per transect in Batam but strangely there was an increase by 47.36 individuals per transect for Natuna. This increase might be related to the isolated location of Natuna, which prevented fishes from migration, especially juveniles. In the same year, the benthic compositions in both locations changed from Acroporidae dominated reefs to become less complex reefs. Following this, the fish composition became less diverse for Batam but in reverse for Natuna. The changes in benthic communities correlate significantly with fish functional group diversity for Batam and the abundance for Natuna. These differences might be related to geographical conditions and human impacts which are different between the locations, such as being surrounded by group of islands or open sea, and fishing activities. The communities are dynamic spatially and temporally as a result of natural conditions of the environment and human activities.

Diel variation of ichthyoplankton recruitment in a wind-dominated temperate coastal lagoon (Argentina)

This study aimed to assess the diel changes of ichthyoplankton occurrence, during a known recruitment period, to a wind-dominated coastal lagoon (Argentina). We collected plankton samples at three sites of the lagoon's inlet area every 3 h during four 24 h cycles in mid austral summer. For each early-life history stage (eggs, yolk sac, preflexion larvae, postflexion larvae and early juveniles), the relationship between the abundance and possible combinations of the time of sampling, the wind effect, the wave period and the tidal state was evaluated by fitting generalized linear mix-effects models (GLMM). The wind effects depending on the time of sampling mainly affected fish abundance in all developmental stages. Overall, the highest abundances were collected at nocturnal hours when low-speed offshore winds blew. In addition, higher abundances of eggs, yolk sac and preflexion larvae were related to the incoming flood tide; whereas higher abundances of postflexion larvae and early juveniles were related to longer wave periods. We argued that the daily variation in the abundance of early-life history stages of fishes is related to the sea-land breeze cycle. Therefore, a conceptual framework of the recruitment process of eggs, larvae and early juveniles of fishes into this estuarine system considering the daily effect of winds is proposed.

Re-examining the relationship between invasive lionfish and native grouper in the Caribbean.

Biotic resistance is the idea that native species negatively affect the invasion success of introduced species, but whether this can occur at large spatial scales is poorly understood. Here we re-evaluated the hypothesis that native large-bodied grouper and other predators are controlling the abundance of exotic lionfish (Pterois volitans/miles) on Caribbean coral reefs. We assessed the relationship between the biomass of lionfish and native predators at 71 reefs in three biogeographic regions while taking into consideration several cofactors that may affect fish abundance, including among others, proxies for fishing pressure and habitat structural complexity. Our results indicate that the abundance of lionfish, large-bodied grouper and other predators were not negatively related. Lionfish abundance was instead controlled by several physical site characteristics, and possibly by culling. Taken together, our results suggest that managers cannot rely on current native grouper populations to control the lionfish invasion.

How well do sunken vessels approximate fish assemblages on coral reefs? Conservation implications of vessel-reef deployments

The amount of artificial habitat (termed ‘artificial reef’, AR) in marine systems is rapidly increasing, yet the effect of most types of AR on reef communities remains unknown. We examined the role of well-established vessel-reefs in structuring coral reef fish assemblages by comparing assemblages on 7 World War II wrecks (>65 years old) to those on interspersed coral patch reefs of comparable size in a tropical lagoon. Fish abundance, species richness, diversity and feeding guild structure on wrecks were similar to natural reefs; however, species composition differed between the two reef types (R = 0.189–0.341, average dissimilarity: 67.3–68.8 %). Despite being more species-rich and diverse, fish assemblages on larger wrecks were less similar to assemblages on their adjacent natural reefs than smaller wrecks. Wrecks may also have affected fish abundance on adjacent natural reefs, with reefs adjacent to larger wrecks supporting higher abundances than reefs adjacent to smaller wrecks. Our results indicate that increases in vessel-reef habitat may not greatly affect reef fish assemblage parameters, but may affect the relative abundances of particular species.

Interactive effects of abiotic, hydrological and anthropogenic factors on fish abundance and distribution in natural run‐of‐the‐river shallow lakes

AbstractEcological processes in lowland rivers are mostly dominated by hydrology and its interactions with other environmental factors. Fish–habitat relationships in rivers are also influenced by human impacts.In this study, we describe patterns of abundance and distribution of fish species in a group of natural lowland river lakes along spatial anthropogenic and abiotic gradients when four hydrologically different summers are compared. We also describe the proportion of the total variances in fish species abundances that can be accounted for by selected abiotic (water conductivity), hydrological (water residence time) and human activity‐derived (total phosphorus (TP) concentration and NO3:NH4) variables. Consequently, our main purpose is to explore how abiotic and anthropogenic factors interact to affect fish abundance and distribution together with consistent results across different hydrological conditions. We conclude with a briefly discussion of some management implications.The anthropogenic impacts on water quality, the extreme hydrological variability and the fluctuating abiotic environment affected fish abundance and distribution. Pampa inland silverside Odontesthes bonariensis was benefited from a less human disturbed environment with higher water residence time and total salinity, whereas species as Cyphocharax voga, Parapimelodus valenciennis and Cyprinus carpio found these conditions largely disadvantageous. On the other hand, while most species showed stronger—either negative or positive—response to anthropogenic, hydrological or abiotic factors Oligosarcus jenynsii was only slightly affected.This paper identified the ecological function of a lowland river under its natural flow regime. There are not many opportunities to study unmodified rivers worldwide. Therefore, our findings may help in assessment programmes of fish communities in flow altered and human disturbed aquatic ecosystems. Copyright © 2008 John Wiley & Sons, Ltd.

Approaches for Determining Effects of Pollution on Fish Populations of Puget Sound

Puget Sound is a large marine and estuarine ecosystem in Washington State that serves as the habitat for a number of recreationally and commercially important species of groundfish and Pacific salmon Onchorhynchus spp. Over the past several decades, the human population of the Puget Sound drainage basin has increased substantially, resulting in increased habitat degradation and chemical pollution. There is now a body of evidence showing that groundfish and salmon in Puget Sound are experiencing a range of biological effects from chemical contaminant exposure, including impairment of several stages in the reproductive process, increased susceptibility to pathogens resulting from altered immune competence, and development of toxicopathic diseases. Preliminary studies suggest the potential for reduced survival of fish from urban areas of Puget Sound resulting from increased infectious and idiopathic diseases. The question that now must be addressed is whether contaminant-related reductions in reproductive and survival rates are sufficient to affect fish abundance in Puget Sound. In the current study, the potential impact of contaminant-related mortality and reproductive impairment on the population growth rate of English sole Pleuronectes vetulus was examined by simulation modeling. An initial Leslie matrix population model was constructed for investigation of contaminant effects. The adult mortality rate for English sole in Puget Sound was estimated from recent historical data. Age-specific fecundity was determined from previously collected English sole ovary samples. Existing data on the effects of contaminants on reproduction, including impaired gonadal development, reduced spawning ability, and decreased egg and larval viability, were incorporated into the fecundity component of the model. The influence of density-dependent population regulation on model results was also examined. Results suggest that declines in the fecundity component of the model, like those observed in field studies of fish from contaminated sites such as the Duwamish Waterway and Eagle Harbor, could substantially decrease the population growth rate (r) if density dependence is weak or moderate, Estimated declines in r are comparable in magnitude to those associated with typical levels of commercial fishing pressure, However, a compensation for loss of recruits due to contaminant effects is observed if strong density-dependent population regulation is assumed.

Disturbance impact on reef fish communities in Reunion Island (Indian Ocean)

Coral reefs in Reunion Island are subjected to eutrophication due mainly to anthropogenic activities following urbanisation of the watershed. This study assesses the impact of consequent coral reef degradation on fish communities. A quantitative study on fish communities was conducted on two sectors (undisturbed and disturbed) of a fringing reef. Data were collected using visual census techniques. The ichthyofauna is structured into three main communities (back reef, inner reef and outer reef). No significant difference was found between the undisturbed and disturbed sectors for the outer reef flat communities. Reef perturbation was found to affect fish abundance mainly on the back reef zone. In the undisturbed back reef zone, the overall fish abundance was almost double that in the disturbed one. The fish communities of the former showed higher homogeneity than the latter. Perturbation of the behaviour of the most abundant fish populations of the back reef zone is discussed with respect to their ecological preferences. Species may also be affected by disturbance, owing to their changing habitat and food availability.