Total Fish Density Research Articles

Observations of deep-sea fishes and mobile scavengers from the abyssal DISCOL experimental mining area

Abstract. Industrial interest in deep-sea mineral extraction began decades ago, and today it is at an all-time high, accelerated by global demand for metals. Several seafloor ecosystem disturbance experiments began in the 1970s, including the Disturbance and Recolonization experiment (DISCOL) conducted in the Peru Basin in 1989. A large seafloor disturbance was created by repeatedly ploughing the seafloor over an area of ∼10.8 km2. Though a number of studies in abyssal mining regions have evaluated megafaunal biodiversity and ecosystem responses, few have included quantitative and detailed data on fishes or scavengers despite their ecological importance as top predators. We used towed camera transects (1989–1996, 2015) and baited camera data (1989–1992) to evaluate the fish community at the DISCOL site. The abyssal fish community included 16 taxa and was dominated by Ipnops meadi. Fish density was lower in ploughed habitat at 6 months and 3 years following disturbance but thereafter increased over time. Twenty-six years after disturbance there were no differences in overall total fish densities between reference and experimental areas, but the dominant fish, I. meadi, still exhibited much lower densities in ploughed habitat, likely avoiding these areas and suggesting that the fish community remains affected after decades. At the scale of industrial mining, these results could translate to population-level effects. The scavenging community was dominated by eelpouts (Pachycara spp.), hermit crabs (Probeebei mirabilis) and shrimp. The large contribution of hermit crabs appears to be unique amongst abyssal scavenger studies worldwide. The abyssal fish community at DISCOL was similar to that in the more northerly Clarion–Clipperton Zone (CCZ), though some species have only been observed at DISCOL thus far. Also, further species-level identifications are required to refine this assessment. Additional studies across the polymetallic nodule provinces of the Pacific are required to further evaluate the environmental drivers of fish density, diversity and species biogeographies. This information will be important for the development of appropriate management plans aimed at minimizing human impact from deep-sea mining.

Fluctuations in coral reef fish densities after environmental disturbances on the northern Great Barrier Reef.

Global warming is predicted to increase the frequency and or severity of many disturbances including cyclones, storms, and prolonged heatwaves. The coral reef at Lizard Island, part of the Great Barrier Reef, has been recently exposed to a sequence of severe tropical cyclones (i.e., Ita in 2014 and Nathan in 2015) and a coral bleaching in the year 2016. Reef fishes are an essential part of the coral reef ecosystem, and their abundance is thus a good marker to estimate the magnitude of such disturbances. Here, we examined whether the recent disturbances at Lizard Island had an impact on the coral reef fish communities. To do this, we examined fish survey data collected before and after the disturbances for potential changes in total fish density post-disturbance. Also, by sorting fish species into 11 functional groups based on their trophic level (i.e., diet), we further explored the density changes within each functional group. Our findings showed an overall decline of 68% in fish density post-disturbance, with a significant density decrease in nine of 11 trophic groups. These nine groups were: browsers, corallivores, detritivores, excavator/scrapers, grazers, macro-invertivores, pisci-invertivores, planktivores, and spongivores. The piscivores, on the other hand, were the only “winners,” wherein their density showed an increase post-disturbance. These changes within functional groups might have a further impact on the trophodynamics of the food web. In summary, our findings provide evidence that the fish assemblage on the reefs around Lizard Island was considerably affected by extreme weather events, leading to changes in the functional composition of the reef fish assemblage.

Landscape features determine brown trout population structure and recruitment dynamics

AbstractVariation in brown trout (Salmo trutta L.) population recruitment and structure is related to migratory patterns, which should depend on ease of access to habitats providing increased opportunity for growth. We quantified the number of young of year (YOY) as a proportion of the total number of brown trout at 24 locations on 11 streams within the Taieri catchment, New Zealand, including back calculated growth rates and emergence dates from otoliths. Locations with high absolute and relative abundance of YOY fish were related to elevation and distance from the river mainstem (habitat used by migratory fish), fish density, and the interaction between invertebrate food biomass, distance and elevation. Hatch date and growth were not related to the proportion of YOY fish, though growth was negatively correlated to total fish density. We suggest landscape features play a large role in determining recruitment and population structure. Locations at lower elevations have a high YOY density, high competition and lower growth, likely prompting out‐migration. These conditions could be created by successful return migration and spawning of large fecund fish resulting in YOY densities exceeding the habitat carrying capacity. Environmental factors, such as food availability, also played a role in determining population structure. These results provide an example of how population structure and recruitment might be controlled by local conditions and access to high growth environments in wild populations of introduced brown trout across a catchment.

Density of the Fish Population in River Channel Parts of the Ivankovo Reservoir in 2012–2015

The density of some species and total density of fishes have been estimated in river channel parts of the Ivankovo Reservoir in 2012–2015. The significant differences in the total abundance of fishes in 2012–2013 and 2014–2015 have been revealed. The increase in the number of tyulka (Clupeonella cultriventris (Nordmann, 1840)) in the Black and Azov seas in 2014–2015 was determined by their periodic fluctuations typical for any species with a short life cycle. Changes in the abundance of bream and silver bream in the reservoir pelagial relate to their vertical redistribution under the effect of environment factors.

How many fish? Comparison of two underwater visual sampling methods for monitoring fish communities.

BackgroundUnderwater visual surveys (UVSs) for monitoring fish communities are preferred over fishing surveys in certain habitats, such as rocky or coral reefs and seagrass beds and are the standard monitoring tool in many cases, especially in protected areas. However, despite their wide application there are potential biases, mainly due to imperfect detectability and the behavioral responses of fish to the observers.MethodsThe performance of two methods of UVSs were compared to test whether they give similar results in terms of fish population density, occupancy, species richness, and community composition. Distance sampling (line transects) and plot sampling (strip transects) were conducted at 31 rocky reef sites in the Aegean Sea (Greece) using SCUBA diving.ResultsLine transects generated significantly higher values of occupancy, species richness, and total fish density compared to strip transects. For most species, density estimates differed significantly between the two sampling methods. For secretive species and species avoiding the observers, the line transect method yielded higher estimates, as it accounted for imperfect detectability and utilized a larger survey area compared to the strip transect method. On the other hand, large-scale spatial patterns of species composition were similar for both methods.DiscussionOverall, both methods presented a number of advantages and limitations, which should be considered in survey design. Line transects appear to be more suitable for surveying secretive species, while strip transects should be preferred at high fish densities and for species of high mobility.

Fish assemblages along the coasts of Tunisia: a baseline study to assess the effectiveness of future Marine Protected Areas

The present study investigated coastal fish assemblages, using Underwater Visual Census (UVC) transects, in Tunisia (south Mediterranean basin). The rationale behind this work is to get i) a suggestive evidence about the status of fish assemblages, and ii) baseline data at 3 locations in Tunisia where 3 MPAs will be established, before the implementation of protection measures. At each location, we used a sampling design where fish censuses were performed in two types of zone: zones that will be inside MPAs, and zones that will remain outside. On the whole, 49 taxa belonging to 19 families were censused. Data reveal clear symptoms of overfishing, especially in terms of dominance of small- and medium-sized individuals of commercially relevant species. Our analyses, moreover, did not show any significant difference in whole fish assemblage structures (considering both density and biomass), patterns of average species richness, total fish density and biomass, density and biomass of different trophic categories of fishes, size distribution of commercially relevant species, between future-protected and unprotected zones. Overall, results suggest that 1) current fish assemblages at the three studied locations are likely to be seriously impacted by fishing activities, and 2) these data could be used as reliable baselines to assess the effectiveness of protection measures within the MPAs that will be established in the future. Our study is the first in Tunisia, and in North African coasts, that assessed distribution patterns of coastal fish assemblages by means of UVC, using a formal spatially replicated sampling design for resource management.

Spatiotemporal variation in wetland fish assemblages in the Western Ghats region of India

The Western Ghats region of peninsular India contains high diversity of freshwater fishes that support artisanal fisheries, but no studies to date have investigated fish assemblages of the region's extensive wetlands. This study examined fish population densities and the structure of local species assemblages in pools of the Periyakulam wetland of the Western Ghats. From 2000 to 2001, fishes and local abiotic environmental parameters were surveyed during three periods with contrasting rainfall (dry, major wet, minor wet). We hypothesized that fish density would be higher during the dry season when aquatic habitat is reduced, and that local assemblage structure would be strongly associated with habitat conditions. Total fish densities were higher during the dry season, but the magnitude of seasonal change was relatively low, and this apparently was because changes in water depth were minimal due to operation of sluice gates that control wetland hydrology. Chanda nama, Pseudetroplus maculatus, Rasbora daniconius, and Danio aequipinnatus were dominant species in most habitats during all three seasons. Multivariate ordinations revealed strong associations between assemblage structure and habitats based on vegetation cover. Local assemblages in shallow-vegetated habitats varied seasonally in association with gradients of rainfall and water quality parameters. Spatial variation of local fish assemblages in the Periyakulam wetland appears to be maintained by species-specific habitat selection. Although hydrologic regulation probably has reduced seasonal variation in the structure of local assemblages, seasonal differences still occur and appear to be caused by species differences with regard to periods of reproduction, recruitment, dispersal and habitat selection.

Predator foraging strategy mediates the effects of predators on local and emigrating prey

Predation is a dominant structuring force in ecosystems, but its effects are almost always measured in the ecosystem of the predator. However, the effects of predators can potentially extend across ecosystem boundaries during ontogenetic niche shifts in prey. We compared the effects of fish predation on benthic versus emerging aquatic insects, and hypothesized that the relative effects of fish on these two stages of prey are mediated by fish foraging strategy (benthic versus water‐column feeders). Benthic‐feeding smallmouth buffalo reduced benthic insect biomass in the freshwater ecosystem by 89%, and reduced insect emergence to the terrestrial ecosystem by 65%. In contrast, water‐column feeding sunfish had no effect on benthic biomass in the freshwater ecosystem, but reduced emergence to the terrestrial ecosystem by 44% relative to the fishless control. When smallmouth and sunfish were combined in a substitutive design that kept total fish density the same as the single species treatments, their effects on benthic insects (50% reduction) were weaker than expected based on predictions from the single species treatments. In contrast, their combined effects on emergence (46% reduction) were additive. Tetragnathid spider densities increased during peak emergence, but did not respond to changes in emergence among treatments. These results demonstrate that the effects of fish on prey flux to the terrestrial ecosystem are not the same as their effects on benthic prey biomass in the aquatic ecosystem, and that this difference is likely mediated by foraging strategy.

A Comparison of Fishes and Invertebrates Living in the Vicinity of Energized and Unenergized Submarine Power Cables and Natural Sea Floor off Southern California, USA

Increasing reliance on deep-water renewable energy has increased concerns about the effects of the electromagnetic fields (EMFs) generated by submarine power cables on aquatic organisms. Off southern California, we conducted surveys of marine organisms living around energized and unenergized submarine power cables and nearby sea floor during 2012–2014 at depths between 76 and 213 m. In general, EMFs declined to background levels about one meter from the cable. We found no statistical difference in species composition between the fish assemblages along the energized and unenergized cables. The natural habitat community statistically differed from both energized and unenergized cable communities. Within species (or species groups), we found no differences in densities between energized and unenergized cables. Total fish densities were significantly higher around the cables than over the natural habitat. We found that invertebrate communities were structured by habitat type and depth and, similar to the fishes, there was no statistical difference between the energized and unenergized cables. Individually, the densities of four invertebrate species or species groups (Metridium farcimen, Luidia spp., unidentified black Crinoidea, and Urticina spp.) differed between energized and unenergized cables, but this difference was not significant across all depth strata. The invertebrate community inhabiting the natural habitat strongly differed from the energized and unenergized cable community exhibiting the fewest species and individuals.

Response of fish communities in rivers subjected to a high sediment load

Erosion and sediment yield are a significant problem in the Guadalquivir River basin. Such phenomena are largely driven by a land use devoted to intensive cultivation of olive trees, with a large socioeconomic influence in Andalusia. This sediment overload in rivers causes serious impacts on all fluvial ecosystem components. In this study we assess the chronic effect of sediment yield on fish communities at 104 river sites located in two different sub-catchments – the Bembézar and Guadajoz rivers – both with different lithological composition and erosion rates. Sediment yield was estimated using a semi-quantitative Factorial Score Model (FSM), developed specifically for Spanish rivers. The fish populations of both basins were evaluated in composition and abundances by the study of Fernández-Delgado et al., 2014. The influence of sediment yield on the fish community was analyzed using General Additive Models. The sediment yield was higher in the Guadajoz basin (921 T/Km2 per year) than in Bembézar (701 T/Km2 per year). In the former, fish communities were poorer in both fish density and diversity, with Luciobarbus sclateri as the only substantially present species and a significant relationship between sediment yield and load, and fish density. In contrast, in the Bembézar basin, sediment yield was correlated with total fish density, including Luciobarbus sclateri, Pseudochondrostoma willkommii, Cobitis paludica, Iberochondrostoma lemmingii, Anaecypris hispanica, and Cyprinus carpio. Intermediate values of sediment yield led to maximum densities, while those higher decreased the density of these species.

Using fish guilds to assess community responses to temperature and flow regimes in unregulated and regulated Canadian rivers

Summary Hydropower currently accounts for 63% of Canada's total electricity generation and is bound to increase with the energy demands of a growing population. With damming and flow regulation known as major threats to aquatic biodiversity and river and floodplain habitats, an improved understanding of the specific impacts of river regulation is needed for the proper management of these systems. Although interactions among river flow and thermal regimes have been described in the literature, their concurrent influence on fish guild responses has yet to be analysed for temperate rivers. Such an analysis may be used to identify the ecological traits linked with the flow and thermal variables reflecting river regulation. Extensive field surveys were conducted across 25 unregulated and regulated rivers to estimate fish species density and biomass. Fish guild models were developed to characterise morphologic, trophic, reproductive, habitat preferences and behavioural traits, as well as phylogenetic associations. To characterise ecologically relevant components of the flow and thermal regimes of rivers, we calculated indices based on the magnitude, frequency, duration, timing and rate of change in each driver. Model relationships between fish biomass and density estimates were then run using redundancy analyses (RDA) on each type of guild and dominant patterns of flow and thermal variability. Variables representing the magnitude of summer temperatures and intra‐annual flow variability were consistently selected as independent drivers of fish guild responses (>86% of RDA models), clearly showing the importance of integrating thermal regimes in current river hydro‐ecological studies. Fish guild density and biomass were significantly explained (R2Adj = 25–44%) and predicted (R2CV = 35–76%) by flow and thermal variables characterising regimes across unregulated and regulated rivers, whereas total fish density and biomass were not. Fish guild models based on trait–environmental relationships performed better than those based on phylogeny. Our results also showed that the models describing habitat and trophic guilds had the greatest explanatory power (R2Adj = 0.44 and R2Adj = 0.41 respectively). This study identified differences in guild trait–environment relationships across rivers and the guilds most susceptible to changes in flow and temperature conditions resulting from river regulation. In particular, more constant summer temperatures and lower flow variability favoured habitat and trophic guilds over morphologic, reproductive and behavioural guilds. Our results showed that maintaining particular aspects of the flow and thermal regime may be important for ensuring the presence of certain guilds in temperate rivers.

Fish Assemblages, Habitat Conditions, and Grazing Effects in Rolling Prairie and Badlands Streams of the Northern Great Plains

Fish sampling was conducted over a two-year period (May to August, 2004 and 2005) in seven streams traversing the Little Missouri River National Grassland and Theodore Roosevelt National Park, western North Dakota. Fish communities of the two stream types in the region (rolling prairie and badlands) differed significantly despite their close geographic proximity, overlapping by only 18% in species composition and having only 8 of the 21 total fish species in common. As summer progressed, rolling prairie streams showed an increase in total fish density while total fish density in badland streams decreased. Badland and rolling prairie stream fish communities responded differently to the physical habitat variables of pool surface area, volume, mean depth, maximum depth, and width-to-depth ratio. Fish in badland streams appeared to be more susceptible to rapid physical habitat changes associated with late summer dewatering, while the more stable flows of rolling prairie streams prevented significant isolation...

Seasonal shift in boreal riverine fish assemblages and associated bias in bioassessment

Collated electrofishing data from wadeable riffles of boreal rivers in Finland revealed a substantial shift in the fish assemblage composition, accompanied by a decline in total fish density and a reduction in species richness from early summer to late autumn. As the major changes in fish assemblages, the density of cyprinids decreased sharply from June towards autumn, whereas salmonids peaked in September. These shifts were considered to originate mainly from spawning migrations, fish movements to winter refuge habitat and other temperature-related responses of rheophilic versus eurytopic fish species. Temporal change in fish assemblages induced a prominent variation in the monthly fish-based index values used for bioassessment. The proportion of sampled sites classified as high or good in ecological status within the Water Framework Directive (WFD) based on fish increased from 25.9% in July to 68.3% in October. These results, combined with the observed timing of young of the year (0+) fish recruitment to electrofishing catch, suggest that sampling of fish in boreal rivers for WFD monitoring should be restricted to a considerably shorter period than the prevailing practice in order to avoid temporal bias.

Recovery of young brown trout (Salmo trutta) in acidified streams: What are the critical values for acid-neutralizing capacity?

The recovery of young allopatric brown trout (Salmo trutta) grouped into YoY (age 0+) and older parr (age ≥1+) fish, was studied in acid-sensitive streams in a Norwegian watershed during a 24-year-period (1987–2010). Their abundance was assessed by electrofishing. Most sites typically had 5.0–5.5 in pH, 0.4–0.7 mg L−1 Ca, 10–20 μg L−1 inorganic toxic aluminum (Ali) and acid-neutralizing capacity adjusted for organic acids (ANCOAA) of - 15 to +25 μeq L−1. Densities of both YoY and older parr increased significantly during the study period. Water quality also improved in recent years with respect to pH (5.8–6.0), Ali (5–15 μg L−1) and ANCOAA (10–20 μeq L−1). However, some negative trends in both fish density and water chemistry were found during both the first (1987–1993) and last years (2004–2008) of the study. Initially, YoY densities remained at about 16–20 specimens 100 m−2 (1987–1990), declined to 10–15 specimens 100 m−2 in the early/mid 1990s, and rosed to 30–50 specimens 100 m−2 in recent years (1997–2010). Their densities correlated significantly with ANCOAA, and at least three stages in the recovery process were recognised: (i) Low density with 10–20 specimens 100 m−2 at −18 to −5 μeq L−1, (ii) medium and unstable density with 20–30 specimens 100 m−2 at −5 to 10 μeq L−1, and (iii) increasing density to 40–50 specimens 100 m−2 at 10–25 μeq L−1. The decline in brown trout density in the early-mid 1990s coincided with high sea salt depositions, which caused increased acidification. Component 1 in a PCA explained 51% of the variation in fish densities, including conductivity, Mg, Ca, Na, alkalinity and TOC. Component 2 explained an additional 31% of the variation, including pH, Ali and ANCOAA. Multiple regression analysis coefficients showed that the two components explained 41% of the variance in total fish density. Young brown trout suffered a high mortality during the initial phase of the study in spite of relative low levels of Ali. This is probabaly because the study streams have very diluted water. The densities of young brown trout have levelled off in recent years, indicating a development towards reaching carrying capacity and hence full recovery. However, still some annual fluctuations in density are recorded, which may be related to an unstable water chemistry.

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.

High resolution study of the spatial distributions of abyssal fishes by autonomous underwater vehicle.

On abyssal plains, demersal fish are believed to play an important role in transferring energy across the seafloor and between the pelagic and benthic realms. However, little is known about their spatial distributions, making it difficult to quantify their ecological significance. To address this, we employed an autonomous underwater vehicle to conduct an exceptionally large photographic survey of fish distributions on the Porcupine Abyssal Plain (NE Atlantic, 4850 m water depth) encompassing two spatial scales (1–10 km2) on and adjacent to a small abyssal hill (240 m elevation). The spatial distributions of the total fish fauna and that of the two dominant morphotypes (Coryphaenoides sp. 1 and C. profundicolus) appeared to be random, a result contrary to common expectation but consistent with previous predictions for these fishes. We estimated total fish density on the abyssal plain to be 723 individuals km−2 (95% CI: 601–844). This estimate is higher, and likely more precise, than prior estimates from trawl catch and baited camera techniques (152 and 188 individuals km−2 respectively). We detected no significant difference in fish density between abyssal hill and plain, nor did we detect any evidence for the existence of fish aggregations at any spatial scale assessed.

The density dependent interspecific competition between nonnative salmonids, rainbow trout and brown trout

Interspecific interactions play a key role in determining species assemblages when nonnative species are introduced. In the Chitose River system, Hokkaido, northern Japan, nonnative brown trout Salmo trutta may have replaced nonnative rainbow trout Oncorhynchus mykiss due to interspecific competition. The outcome of this competition is predicted to be influenced by the density of both species. Then, I conducted an enclosure experiment to test whether density-dependent interspecific competition between YOY (young-of-the-year) of these species may have explained the species replacement. Rainbow trout decreased their stomach contents in the high density treatment sympatry with brown trout, and growth rate of rainbow trout decreased in the high density treatments both allopatry and sympatry with brown trout. Stomach contents and growth of brown trout were not affected by competitor species (rainbow trout) or total fish density. These results imply that brown trout are competitively superior to rainbow trout. Therefore, there is the potential for the replacement of rainbow trout by brown trout through interspecific competition.

Effects of habitat change from a bare sand/mud area to a short seagrass Halophila ovalis bed on fish assemblage structure: a case study in an intertidal bay in Trang, southern Thailand

Fish assemblage structures in an intertidal sand/mud area invaded by short seagrass Halophila ovalis and a nearby non-invaded sand/mud area in Trang Province, Thailand, were examined in detail by visual census to elucidate the effects of such habitat change on assemblage structure. The assemblage structure in the newly established seagrass bed showed a significant shift from that in the sand/mud area, despite the total fish species numbers remaining similar to each other (i.e., 30 and 29 species, respectively). Total fish density was significantly lower in the seagrass bed. In addition, differences in density patterns of component species between seagrass and sand/mud fish assemblages were evident, some fish species being restricted to or more abundant in the alternative habitat. Such differences may have arisen, at least in part, from differences in practical food availability/accessibility between the two habitat types, and/or specific microhabitat preferences of the resident fishes. Although seagrass habitats are often regarded as supporting a richer fish assemblage compared with bare sand/mud areas, the present study clearly indicated that the latter also supported a unique fish assemblage, including juveniles of fishery target species. Accordingly, both seagrass and bare sand/mud habitats should be taken into consideration for both the conservation of greater overall biodiversity in the coastal environment and the continued existence of local fisheries.

Environmental and socioeconomic assessment of a poorly known coastal section in the southern Mexican Caribbean

The Uvero-Punta Piedras section, a low-developed coastal strip located in the southern area of Quintana Roo, Mexico, is experiencing habitat degradation driven by unplanned population sprawl, unregulated tourism expansion and overfishing. The main objective of this study is to provide an environmental (coastal vegetation and coral reef condition) and socioeconomic (human population condition) baseline data of a poorly documented and weakly managed zone by the use of a set of rapid assessment methodologies, looking to assist the regional efforts to manage these coastal resources. To achieve this goal we used a series of surveying methods including remote sensing, geographic information systems and in situ land/underwater surveys, to allow a broad characterization of the resources' condition in the study zone. Results showed that reef habitat was dominated by macro-algae (61.2 ± 7.6%), followed by soft coral (gorgonians, 12.4 ± 4.1%), hard coral (8.2 ± 5.1%) and sponges (2.5 ± 1.3%). Zooanthids and tunicates represented less than 1% of the total; coral and macro algae estimates suggest a decline from records of 15 years ago. Highest fish densities were (144 ± 124 individuals/100 m2), while lowest were (83 ± 25 individuals/100 m2). The total average fish density recorded could also be reflecting a decrease trend in the reef community structure. The main economic activities in the area are fishing and land clearing. From December 2003, 22% (corresponding to 44 ha) of the total original vegetation cover in the studied area was deforested. By February 2007, the deforested area increased 4.4 ha more. Should this tendency continue, by 2025 it would only maintain 24% of its total coastal vegetation cover representing a huge habitat loss. The future of economic activities in these areas lie directly on the establishment of appropriate management strategies for the protection and conservation of the renowned biodiversity that this area comprises.

Invasive Pacific lionfish Pterois volitans reduce abundance and species richness of native Bahamian coral-reef fishes

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 522:231-243 (2015) - DOI: https://doi.org/10.3354/meps11159 Invasive Pacific lionfish Pterois volitans reduce abundance and species richness of native Bahamian coral-reef fishes Mark A. Albins* Department of Zoology, Oregon State University, Corvallis, Oregon 97331, USA Present address: School of Fisheries, Aquaculture, and Aquatic Sciences, Auburn University, Gulf Coast Research and Extension Center, 8300 State Highway 104, Fairhope, Alabama 36532, USA *Corresponding author: mark.albins@auburn.edu ABSTRACT: Pacific red lionfish Pterois volitans, introduced to Atlantic waters in the 1980s, represent a particularly successful invasive marine predator with strong effects on native prey. Previous experiments examining the effects of lionfish on native fish communities have been conducted on small patch reefs. However, the effects of lionfish on native reef-fish communities over larger spatial scales—scales at which conservation and management efforts are typically applied—have not been examined experimentally. Beginning in June 2009, I conducted a large-scale field experiment near Lee Stocking Island, Bahamas. Ten large (1400 to 4000 m2) coral reefs were paired based on location and similarity of habitat, and baseline surveys of their fish communities were conducted. Quarterly removals of lionfish were then conducted on 1 reef in each pair, while the densities of lionfish on the other reefs were standardized at typical post-invasion levels. Through August 2010, quarterly surveys showed that lionfish caused significant changes in native reef-fish communities, including reductions in the total density (up to 46.3 ± 13.7%, mean ± SEM), biomass (31.9 ± 10.7%), and species richness (21.4 ± 9.1%) of prey-sized fishes (all individuals <10 cm total length). Lionfish also caused substantial reductions in the biomass of prey-sized herbivorous fishes (33.9 ± 16.0%) and piscivores (98.6 ± 39.5%). However, these negative effects on small fish did not translate to observable declines in a larger size-class (all individuals 10 to 20 cm total length) over the 14 mo study period. KEY WORDS: Coral reefs · Invasive species · Marine fishes · Predator effects · Prey species richness Full text in pdf format Supplementary material PreviousNextCite this article as: Albins MA (2015) Invasive Pacific lionfish Pterois volitans reduce abundance and species richness of native Bahamian coral-reef fishes. Mar Ecol Prog Ser 522:231-243. https://doi.org/10.3354/meps11159 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 522. Online publication date: March 02, 2015 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2015 Inter-Research.