Fish Nursery Areas Research Articles

Macrophyte banks and fish early stages in a cascade of small hydropower reservoirs (south-eastern Brazil): temporal changes along the reproductive cycle and influence of the limnological and spatial organisation

Context Small hydroelectric power plants (SHPs) are worldwide-distributed infrastructures, the ecological impacts of which are still poorly known. Aim To evaluate the role of littoral macrophytes as nursery areas for fishes in a cascade of three SHP reservoirs in south-eastern Brazil. Methods Three random macrophyte banks, from the intermediate and lentic compartments of each reservoir, were sampled (with manual sieves and gillnets) monthly along the peak of the reproductive period. Basic limnological variables were simultaneously measured. Key results In all, 88 larvae and 393 juveniles were captured, corresponding to 29 taxa, constituting almost 30% of the regional pool of fishes in the river. Non-migrants and short-distance migrants (with or without parental care) predominated. The species accumulation curve tended to an asymptotic configuration (whole dataset sampling effort). Fish abundance differed, mainly temporally, and, at a lower degree, spatially. Higher diversity (rarefaction and extrapolation curves) occurred both at the beginning of the reproductive peak and in the first (upstream) reservoir, where there was also a good correspondence between observed and estimated richness, i.e. 90%. Conclusions The macrophyte banks in these SHP reservoirs are effectively used as nursery areas. Implications Results have provided important insights for actions of conservation and management of the local and regional ichthyofauna, in a condition where typical nursery areas do not exist.

Quantification of finfish assemblages associated with mussel and seaweed farms in southwest UK provides evidence of potential benefits to fisheries

Low trophic aquaculture, including shellfish and seaweed farming, offers a potentially sustainable food source and may provide additional environmental benefits, including the creation of new feeding, breeding and nursery areas for fish of commercial and ecological importance. However, quantitative assessments of fish assemblages associated with aquaculture sites are lacking. We used pelagic baited remote underwater videos (BRUVs) and hook and line catches to survey summer fish assemblages at 2 integrated blue mussel Mytilus edulis and kelp (predominantly Saccharina latissima) farms in southwest UK. We recorded at least 11 finfish species across the surveys, including several of commercial importance, with farmed mussels and/or kelps supporting significantly higher levels of abundance and richness than reference areas outside farm infrastructure. Farmed kelp provided temporary habitat due to seasonal harvesting schedules, whereas farmed mussels provided greater habitat stability due to overlapping interannual growth cycles. Stomach content analysis of fish caught at the farms revealed that some low trophic level species had high proportions of amphipods in their stomachs, which also dominated epibiont assemblages at the farms. Higher trophic level fish stomachs contained several lower trophic level fish species, suggesting that farms provide new foraging grounds and support secondary and tertiary production. Although not identified to species level, juvenile fish were abundant at both farms, suggesting potential provisioning of nursery or breeding grounds; however, this needs further verification. Overall, this study provides evidence that shellfish and seaweed aquaculture can support and enhance populations of commercially and ecologically important fish species through habitat provisioning.

Spatio-temporal dynamics of habitat use by fish in a restored alluvial floodplain over two decades

River floodplain channels can serve as reproduction, nursery or refuge areas for fish. Although the complementary use of floodplain and main channels is known, few studies attempted to quantify this use and even fewer analysed its controlling factors. The objectives of this study are (1) to describe the spatio-temporal use of floodplain habitats and to identify their roles as complementary habitats for fish and (2) to analyse how abiotic variations and their modifications under restoration impact habitat use by fish. To meet these objectives, we analysed (Principal Components Analysis and Coinertia Analysis) multi-site data collected over 20 years in eight main channels and 23 floodplain channels of eight restored sectors of the French Rhône River. Results show that habitat use by fish is mainly related to spatial effects, with 37 % of within-sector variance in taxonomic assemblages explained by the stations. As expected, rheophilic species were more abundant in lotic stations and limnophilic species in lentic ones. In addition, we identified an euryecious guild, grouping young of the year taxa (roach, gudgeon, chub, bleak) that used all types of habitats and particularly lentic floodplain channels with short life-span. Temporal effects (with ~10 % of the variance explained by years) combine (1) the effect of restoration, that increased the diversity of fish assemblages across the floodplain, with stronger changes in floodplain channels whose connectivity regime was modified, (2) the effect of high flows on fish habitat use, that reinforces the nursery and refuge functions of floodplain channels. Our results demonstrate the importance of restoring the diversity of habitats and connectivity because floodplain habitats have complementary functions for fish. Furthermore, our results also suggest to account for temporal variations in order to better estimate the potential effects of restoration on river and their floodplains.

Essential and toxic elements in juvenile migratory commercial fish species in the Paraná River alluvial valley (South America): an approach for aquatic environmental monitoring.

The Paraná River is the sixth largest in the world, and the lower section of the river is one of the largest and most productive floodplain wetlands in South America. The alluvial plain is an important habitat for nursery and feeding areas for commercial fish; however, it has been heavily anthropized due to industries, agricultural activities, and the growth and expansion of metropolitan areas. The aim of this study was to determine element accumulation (As, Cd, Cr, Cu, Fe, Mn, Pb, and Zn) in young-of-the-year fish muscle from a floodplain lagoon of the lower Paraná River (Argentina) during summer and winter seasons, in relation with abiotic matrices (water and sediment). Four commercial fish species were assessed: sábalo (Prochilodus lineatus), boga (Megaleporinus obtusidens), dorado (Salminus brasiliensis), and pirapitá (Brycon orbignyanus). The concentrations of eight elements were detected by quadrupole inductively coupled plasma mass spectrometry. In water samples, Cd, Cr, Mn, Fe, and Zn levels were under the permissible limits for aquatic biota protection in both seasons, except for Pb (> 1 μg L-1) and Cu (> 2 μg L-1). In sediment, the average concentrations of all elements were under the limits set by national and international regulatory authorities. Differences in elemental concentrations between species and seasons were found. In general, the levels of elements in water were higher in summer than in winter, while in sediment, the lowest concentrations of elements were detected during the summer. The order of element concentration in fish muscle was Cd (0.01-0.04 μg g-1) < As (0.02-0.16 μg g-1) < Pb (0.03-0.23 μg g-1) < Mn (0.77-4.32 μg g-1) < Cu (1.01-4.07 μg g-1) < Cr (1.09-4.30 μg g-1) < Zn (15.8-31.7 μg g -1) < Fe (12.6-49.7 μg g-1). The accumulation assessment showed that the four fish species significantly accumulate Cr, Cu and Zn, and As and Zn from water and sediment, respectively. The correlation analysis showed a relationship between fish size and As, Cr, Cu, Fe, Mn, and Zn concentrations. Similarly, the highest values of element concentrations in muscle were detected during the summer when the fishes are early juveniles. The level of As, Cd, and Pb detected in B. orbignyanus, M. obtusidens, and P. lineatus juveniles suggested that these species had the potential to be used as biomarkers for assessing accumulation of toxic elements in the environment. Also, this study reveals that the accumulation patterns differ between size and fish species, which should be a considered insight at the moment of selecting a bioindicator to monitor pollution in the ecosystem.

Exploring the demography and conservation needs of hawksbill sea turtles Eretmochelys imbricata in north-west Mexico

AbstractThe hawksbill sea turtle Eretmochelys imbricata is categorized as Critically Endangered on the IUCN Red List and its population has declined by over 80% in the last century. The Eastern Pacific population is one of the most threatened hawksbill populations globally. Western Mexico is the northern distribution limit for hawksbill sea turtles in the Eastern Pacific and recent research indicates that the Mexican Pacific portion of the population is a separate management unit because of the restricted movements of these turtles. Here we use the most complete database of sighting records in the north-west Pacific of Mexico to identify sites where hawksbill turtles are present. We also develop a conservation index to determine the conservation status of hawksbill turtle sites. Our results demonstrate the importance of this region for juveniles and the relevance of rocky reefs and mangrove estuaries as habitats for hawksbill turtles. We identified 52 sites with records of hawksbill turtles. Most of these sites (71%) are not protected; however, sites with high conservation value included islands and coastal sites along the Baja California peninsula that are established as marine protected areas. Reefs and mangrove estuaries relevant for hawksbill turtles are probably also significant fish nursery areas that are important for local fishing communities, creating opportunities for conservation strategies that combine science, local engagement and policy to benefit both local fishing communities and hawksbill sea turtle conservation.

The nursery function of shallow nearshore and estuarine benthic habitats for demersal fishes

Estuaries and shallow marine nearshore areas are highly productive and valuable ecosystems, which provide numerous habitats for fish and support fundamental ecological links with other environments. Yet only a few studies have focussed on fish community patterns across an estuary and marine nearshore gradient concurrently to determine the nursery value of both environments. This research gap is particularly apparent in southern Africa. The main aim of this study was to assess the relative roles of two permanently open estuaries and the adjacent marine nearshore areas of Algoa Bay, on the south coast of temperate South Africa, as settlement and nursery areas for demersal fishes. Soft-bottom habitats in both the estuaries and the nearshore were dominated by early-life stages (postflexion larvae, settlement stage and young-of-the-year fishes), but a significantly greater density of early-life stage fishes was found in the estuarine environment, highlighting the importance of estuarine habitats for demersal fishes within the Algoa Bay nursery seascape. Settlement and nursery habitats also differed by estuarine-association, with the marine nearshore environment dominated by marine and marine estuarine-opportunists, with core settlement and nursery areas for these species located close to estuary mouths, freshwater outlets and harbours. In contrast, the estuarine environment was dominated by marine estuarine-dependent and estuarine and marine species. This highlights the importance of concurrently sampling habitats in marine nearshore and estuarine environments, which allows for a better understanding of the degree of estuarine dependency of marine fish as well as an understanding of the nursery function of coastal habitats.

Community Patterns and Environmental Associations for the Early Life Stages of Fishes in a Highly Transformed Estuary

Estuaries are important fish nursery areas, yet little is known of how environmental forcing influences estuarine fishes during their early life stages. We analyzed environmental and larval-juvenile fish community data in the upper San Francisco Estuary (SFE) from spring to early summer 1995–2017, to better understand drivers of spatiotemporal community patterns in this highly modified estuary. We evaluated community patterns based on the relative abundance and diversity of native and introduced fish in the SFE and their predominant distribution (pelagic, demersal). The upper SFE experienced a downward trend of freshwater outflow and upward trends of temperature and salinity intrusion. Fish relative abundance only showed long-term downtrends for native and introduced pelagic fish groups. The most influential habitat components for relative abundance and diversity of fish groups were in decreasing order: temperature, salinity, Secchi depth, bottom depth, and zooplankton biomass. Early life stages of native and introduced fishes were generally segregated spatially and temporally, with native fishes more associated with cooler, saltier, and higher turbidity habitats during early to mid-spring compared to introduced fishes during late spring to early summer. Community ordination showed that environmental (temperature, salinity, outflow, Secchi depth, and zooplankton biomass) and spatiotemporal factors (month and depth), explained nearly 40% of the total variance. Our results suggest that the shorter duration of planktonic and nektonic stages of demersal fish groups results in higher resiliency compared to pelagic fishes. The declining abundance of pelagic fishes overall seems to be linked to drought effects and human-induced synergistic interactions intensified by climate change.

The role of macroalgae as nursery areas for fish species within coastal seascapes

Abstract One of the most critical ecosystem functions provided by shallow coastal habitats is as nurseries for the juveniles of fish. Many of the studies that have assessed the nursery function of structurally complex coastal habitats have compared seagrass with unstructured sand and mud and as such, seagrass has emerged as the most important coastal nursery habitat for juvenile fishes. Although considerably less work has focussed on the nursery provision of structurally complex macroalgae within coastal nursery seascapes, recent work has started to highlight that the nursery provision of canopy-forming macroalgae may in fact be comparable with that of seagrass. This review collates research published on the important nursery role of macroalgae within both tropical and temperate coastal seascapes and highlights the importance of smaller canopy-forming brown algae from the Fucalean genera (particularly Sargassum spp.) as core nursery areas for juvenile fishes, particularly emperors (Lethrinidae), rabbitfishes (Siganidae), wrasse and parrotfishes (Labridae), goatfishes (Mullidae), groupers (Serranidae), surgeonfish (Acanthuridae) and damselfish (Pomacentridae) within tropical back-reef systems. Similarly, in temperate nursery seascapes, fucoid (Cystoseira spp.) and macroalgae-dominated reefs were important nursery habitats for damselfish (Chromis chromis), groupers and numerous species of wrasse and sparids (Sparidae). Although the overall density of juvenile fish was not shown to be higher in kelp relative to other temperate nursery habitats, kelp was important in the recruitment of Notolabrus celiodotus (wrasse), Paralabrax clathrus (Serranidae), Brachyistius frenatus (Embiotocidae), Heterostichus rostratus (Clinidae) and Sebastes spp. (Scorpaenidae). Although not interchangeable (fish communities were often different), the nursery function of structurally complex macroalgae was found to be similar to that of seagrass in both temperate and tropical seascapes.

Essential fish habitats of demersal fish in the western Arabian Gulf

Information about habitats occupied by aquatic organisms while completing critical stages of their lives, called essential fish habitats, is crucial for their sustainability. In this work, we determine essential fish habitats (nursery and spawning grounds) of several fish species inhabiting Saudi territorial waters in the western Arabian Gulf using data from multiple surveys (2013–2016), geostatistics, and indicator species analysis. We built geostatistical maps of spatial distributions of juvenile and mature fish and examined the strength of association of each species to its observed nursery and spawning areas. Fish nursery areas were generally located in nearshore locations while spawning areas were located in offshore waters. The patterns of nursery and spawning grounds were highly varied among species, supporting a hypothesis of habitat-species heterogeneity: different species use different locations as nursery and spawning grounds. This information can be used as a roadmap for future evidence-based spatial planning and ecosystem-based management.

Physical drivers of epi- and infauna communities related to dominating macrophytes in shallow bays in the Northern Baltic Sea

Shallow coastal bays with dense aquatic phytobenthic communities are important but vulnerable habitats and nursery areas for fish and invertebrates in the Baltic Sea. These habitats are under increasing anthropogenic stress, and understanding their dynamics is a prerequisite for management and conservation. In this study, we examined the effects of isolation of the bay from the sea, water and sediment characteristics, and macrophyte species on the invertebrate communities. In each bay, both epifauna and infauna were sampled in pairs of monospecific patches of dominating habitat-forming macrophytes (Stuckenia pectinata, Chara tomentosa and Ceratophyllum demersum). We found that the invertebrate community was mainly affected by bay isolation, which correlated with other environmental variables, and thus likely drives many processes in the bays. Further, the epifauna community responded to both the median grainsize and geometric standard deviation across both the isolation gradient (S. pectinata alone) and in the S. pectinata - C. demersum macrophyte pair, whereas the median grainsize affected the epifauna in the S. pectinata - C. tomentosa macrophyte pair. The infauna community responded to either the median grainsize or the geometric standard deviation across the isolation gradient and in both macrophyte pairs. Only minor differences between the dominating macrophyte species were seen regarding invertebrate abundance, taxon richness and diversity, although the more structurally complex C. demersum supported the highest epifauna diversity and lowest infauna abundance. However, at local, within bay scale, epifauna communities varied between most pairs of macrophyte species, suggesting that habitat-forming macrophytes have important roles in structuring local invertebrate community patterns. This study emphasizes the complexity of biotic and abiotic interactions within and among shallow coastal bays, and the challenges with studying and comparing processes in these unique ecosystems.

Emerging Sensor Platforms Allow for Seagrass Extent Mapping in a Turbid Estuary and from the Meadow to Ecosystem Scale

Seagrass meadows are globally important habitats, protecting shorelines, providing nursery areas for fish, and sequestering carbon. However, both anthropogenic and natural environmental stressors have led to a worldwide reduction seagrass habitats. For purposes of management and restoration, it is essential to produce accurate maps of seagrass meadows over a variety of spatial scales, resolutions, and at temporal frequencies ranging from months to years. Satellite remote sensing has been successfully employed to produce maps of seagrass in the past, but turbid waters and difficulty in obtaining low-tide scenes pose persistent challenges. This study builds on an increased availability of affordable high temporal frequency imaging platforms, using seasonal unmanned aerial vehicle (UAV) surveys of seagrass extent at the meadow scale, to inform machine learning classifications of satellite imagery of a 40 km2 bay. We find that object-based image analysis is suitable to detect seasonal trends in seagrass extent from UAV imagery and find that trends vary between individual meadows at our study site Bahía de San Quintín, Baja California, México, during our study period in 2019. We further suggest that compositing multiple satellite imagery classifications into a seagrass probability map allows for an estimation of seagrass extent in turbid waters and report that in 2019, seagrass covered 2324 ha of Bahía de San Quintín, indicating a recovery from losses reported for previous decades.

Estuaries – how challenging are these constantly changing aquatic environments for associated fish species?

Much has been written about the abundance of fishes in estuaries, and particularly the value of the littoral zone and associated macrophyte habitats as fish nursery areas. What has not been researched or discussed in the same amount of detail is that estuaries are demanding physico-chemical environments for fishes, yet each year millions of 0 + juveniles are recruited into these supposedly stressful nurseries. This review focuses on three primary variables; salinity, temperature and turbidity, and highlights the ability of estuary-associated fish species to withstand apparent extreme conditions associated with these physico-chemical drivers in order to benefit from the rich food resources and possible low predation rates present within most systems. However, there is increasing evidence that global change, including climate change, is resulting in these driving variables becoming more extreme, which will test even the most eurytopic estuarine species now and in the future.

Macrophytes banks as potential fish nursery areas in small hydropower reservoirs

Abstract: Aim This study verified if the macrophyte banks found in two reservoirs of small hydroelectric plants (SHPs) have a functional ecological role for the initial development of ichthyofauna. Additionally, we compared the differences in the structure of the fish assemblages along each reservoir compartment and between reservoirs. Methods Sampling was performed in March 2018, in lotic, intermediate, and lentic compartments of Palmeiras and Retiro reservoirs, Sapucaí-Mirim River (SP). Three distinct macrophyte banks in each stretch (triplicates), considering the most representative in terms of composition (recurrency/dominance), were sampled, resulting in 18 samples (nine per reservoir). For fish collection we used a sieve of 1 m2 of area, mesh size of 1 mm, which was manually hauled, from the boat, in the marginal aquatic vegetation (three hauls per sample). Simultaneously, we measured basic limnological parameters with a Horiba U-52 water probe, adjacent to the banks. Results The presence of juveniles of all fish orders found in the river, Characiformes, Siluriformes, Synbranchiformes, Gymnotiformes and Cichliformes, demonstrates that, at least in certain moment of their development cycle, the macrophyte banks are used by species with different ecological requirements. It was observed significant statistical differences in the structure of the ichthyofauna along the longitudinal axes of the reservoirs, but not between reservoirs. The same was seen for the limnological data (PCA). Conclusions The macrophyte banks found in the SHPs reservoirs have a potential role as nurseries for the local ichthyofauna, mainly, but not exclusively, for sedentary species and with parental care. This association is ecologically relevant, given the absence of typical lateral habitats for the initial development of the fish fauna. Additionally, despite the reservoirs small size, spatial organization was also important for the assemblage’s structure, with differences in terms of composition, size and development stages along the distinct sampling stretches.

30 years of large river restoration: How long do restored floodplain channels remain suitable for targeted rheophilic fishes in the lower river Rhine?

The ecological efficacy of river restoration projects may change over time, resulting in the loss of their ecological function for targeted species. The goal of this study was to evaluate the rheophilic nursery function of restored floodplain channels over time, by analysing 30 years of monitoring data from 12 restoration projects in the lower river Rhine. We hypothesised that the nursery function would change over time, caused by the combined effects of decreasing flow conditions and succession processes affecting habitat heterogeneity. We found that nursery area suitability for rheophilic fish was almost 4 times higher in two-sided connected channels than in one-sided connected channels, although the response trends of rheophilic fish were similar for both water body types. These response curves showed clear optima with channel age, for rheophilic fish abundance at 13 to 14 years post-restoration, indicating optimal nursery conditions. On the other hand, rheophilic species richness showed a steadily decreasing trend with channel age, suggesting aging channels became less suitable as nursery areas for most rheophilic fish species. The presence of permanent flow was found to be the main driving factor in explaining both rheophilic fish community trends and habitat succession in individual restored channels. We did not observe an effect of habitat heterogeneity on nursery function for rheophilic fish. To create and maintain optimal nursery conditions in restored floodplain channels of strongly anthropogenically influenced rivers such as the river Rhine, we propose a management strategy involving cyclic rejuvenation through human intervention, focusing on restoring permanent flow, with a frequency of on average every 15 years, depending on the rate of aggradation and targeted rheophilic species. We also propose a thorough investigation of the relationship between habitat heterogeneity and nursery success in floodplain channels, as a next step in the identification of suitable nursery areas for rheophilic fishes.

Littoral habitats as major nursery areas for fish species in estuaries: a reinforcement of the reduced predation paradigm

For many decades, the role of estuaries as important nursery areas for fishes was accepted as fact by scientists and environmental managers. At the turn of the 21st century, a question mark was raised in relation to the reduced predation component of the nursery function, with some scientists contending that both large and small piscivorous fish species had access to the estuarine habitats that juvenile fishes in estuaries occupied. If true on a global scale, the nursery designation for these habitats would be compromised and the long-held paradigm that estuaries are important nursery areas for fishes would need to be revised. In this review, I examine the nature of fish nursery areas in estuarine littoral habitats from a mainly predation perspective and, based on a variety of ichthyofaunal and avifaunal studies, come to the conclusion that apart from a few selected estuarine systems, there is limited predation on juvenile fishes in these particular areas. This, coupled with the abundant suitable food resources for juvenile fish from different trophic categories, shelter from high-energy marine wave action and biological connectivity between a variety of submerged and emergent macrophyte communities, renders shallow estuarine littoral areas ideal nursery areas for the juveniles of mostly euryhaline marine fish species, the dominant component of estuarine ichthyofaunas globally. In addition, there are strong indications from the fossil record that these littoral estuarine nursery areas have been functioning since the Devonian, more than 350 million years ago.

Restoring fish habitat values on a tropical agricultural floodplain: Learning from two decades of aquatic invasive plant maintenance efforts

Coastal managers are increasingly challenged with implementing expensive restoration and on-going maintenance programs to reinstate the services and values of floodplains as important fish nursery areas, but access to long-term data to assist with supporting success is lacking. An environmental levy (funded by farmers, Burdekin Shire Council, a local Natural Resource Management group, and Lower Burdekin Water Board) was enacted in 2003 to fund (approximately $20,000/yr AUD) an ongoing aquatic weed removal program (consisting of an aquatic plant weed harvester that removes floating vegetation to a nearby truck for composting in conjunction with boat weed spraying) designed to maintain the delivery of irrigation water as well as promoting productive fish habitat. We repeated a fish and water quality survey first performed in 2001/2002 (September 2017, May 2018) at 10 lagoons (three clear and seven turbid) on the Burdekin floodplain (north Queensland, Australia) to examine whether these maintenance efforts continue delivering the initial values set nearly 20 years ago. A total of 2267 fish from 24 species were caught, May 2018 (post-wet season) survey yielded more fish (24 species) than the September 2017 (late dry season) survey (19 species) which is close to the results of the 2001/02 survey (post-wet season, 17 species; late dry season, 16 species). A Hydrolab (September 2017) revealed that turbid and clear water lagoons had a similar rhythmic diel temperature cycle that posed no thermal risks to fish. Dissolved oxygen had distinct diel periodicity, with clear lagoons having the widest range, reaching established critical minimum thresholds for some floodplain fish, while turbid lagoons were generally less variable (presumably due to less oxygen demand from biological activity). While as long as sugarcane production occurs, excessive nutrients will necessitate continuance of the aquatic weed program; therefore, the funding model in place must remain. This study advocates the need for long-term maintenance programs facilitated by long-term partnerships, and serves as an exemplar model for managers looking to restore coastal floodplains but are challenged with persistent aquatic weed management issues, not only in Australia but also on floodplains elsewhere.

Estuarine fish and tetrapod evolution: insights from a Late Devonian (Famennian) Gondwanan estuarine lake and a southern African Holocene equivalent.

The Waterloo Farm lagerstätte in South Africa provides a uniquely well-preserved record of a Latest Devonian estuarine ecosystem. Ecological evidence from it is reviewed, contextualised, and compared with that available from the analogous Swartvlei estuarine lake, with a particular emphasis on their piscean inhabitants. Although the taxonomic affinities of the estuarine species are temporally very different, the overall patterns of utilisation prove to be remarkably congruent, with similar trophic structures. Significantly, both systems show evidence of widespread use of estuaries as fish nurseries by both resident and marine migrant taxa. Holocene estuaries are almost exclusively utilised by actinopterygians which are overwhelmingly dominated by oviparous species. Complex strategies are utilised by estuarine resident species to avoid exposure of eggs to environmental stresses that characterize these systems. By contrast, many of the groups utilising Devonian estuaries were likely live bearers, potentially allowing them to avoid the challenges faced by oviparous taxa. This may have contributed to dominance of these systems by non-actinoptergians prior to the End Devonian Mass Extinction. The association of early aquatic tetrapods at Waterloo Farm with a fish nursery environment is consistent with findings from North America, Belgium and Russia, and may be implied by the estuarine settings of a number of other Devonian tetrapods. Tetrapods apparently replace their sister group, the elpistostegids, in estuaries with both groups having been postulated to be adaptated to shallow water habitats where they could access small piscean prey. Correlation of tetrapods (and elpistostegids) with fish nursery areas in the Late Devonian lends strong support to this hypothesis, suggesting that adaptations permitting improved access to the abundant juvenile fish within the littoral zone of estuarine lakes and continental water bodies may have been pivotal in the evolution of tetrapods.

DESEMPENHO DOS DIFERENTES MÉTODOS DE AMOSTRAGEM NA CARACTERIZAÇÃO DA ICTIOFAUNA ASSOCIADA AO MANGUEZAL DA PRAIA DE ARPOEIRAS EM ACARAÚ, CEARÁ

Os manguezais são importantes não apenas devido à sua biodiversidade, mas também por sua importância econômica, uma vez que as comunidades que vivem em seu entorno dependem direta e indiretamente da exploração de seus recursos naturais, entre eles os peixes. Nesse contexto, o objetivo do presente trabalho foi caracterizar a ictiofauna do manguezal da praia de Arpoeiras, em Acaraú, CE, bem como testar os métodos mais adequados para amostragem nesse ambiente. Foram utilizadas diferentes artes de pesca, como anzóis, tarrafas e armadilhas (manzuá). Um total de 256 indivíduos foram capturados durante o período de amostragem, distribuídos em 12 espécies, 10 famílias, 5 ordens e 1 classe, com alta dominância para as espécies Lutjanus alexandrei (24,6%), Lutjanus jocu (24,2%), Eucinostomus argenteus (25,7%) e Diapterus auratus (8,9%). A tarrafa foi o equipamento de pesca mais eficiente devido à sua baixa seletividade em comparação com outras artes de pesca utilizadas. Análises referentes ao estágio de maturação, peso (g) e tamanho (cm) dos espécimes coletados mostraram que todos os animais eram sexualmente imaturos. Esses dados confirmam que manguezais são áreas de berçários para peixes, inclusive para espécies de interesse econômico, sendo necessárias medidas para sua conservação.Palavras-chave: caracterização, ictiofauna, manguezal.

Fishing marine debris in a northeast Brazilian beach: Composition, abundance and tidal changes

This study aims to examine the composition and the spatial/tidal changes of marine debris caught with a fishing net during a fishery survey in two different areas of a sand beach at the northeast of Brazil. Samples were conducted weekly, at each moon phase, for two months using a beach seine net in the surf zone. Abundance of debris were estimate by swept area (items·km−1 and g·km−1). A total of 12 categories of debris were recorded. Plastic – both hard and soft types - was the most abundant debris category. Most fragments were classified as macro (20–100 mm) and mega debris (>100 mm). Significant differences (P < 0.05) between areas and tides were registered for plastic, metal and cloth. Spring tides were responsible for the high rates of marine debris found in the surf zone of Miramar beach. The results demonstrate the occurrence and abundance of litter in this fish nursery area and reinforce the need and importance of environmental protection and educational programs. Capsule abstractMarine debris caught by a fishing net in the surf zone of Brazilian beach.

The Pliocene Elizabethtown otolith assemblage (Bladen County, North Carolina, USA) with indications of a primary fish nursery area

ABSTRACT Bulk sampling of Pliocene (2.5–3.1 Ma, Piacenzian) beds at the Elizabethtown locality (Bladen County, North Carolina) produced 745 teleostean otoliths (17 taxa, representing extant fish off the U.S. Atlantic coast). Sciaenids dominate the assemblage (8 taxa; 44.4% of the total) and account for an extremely large percentage of total specimens (93.2%). The number of species (richness) at Elizabethtown is relatively small, and percentage abundance indicates a very large unevenness with Micropogonias undulatus and Leiostomus aff. L. xanthurus (91.4% of the specimens). Otolith assemblages from Elizabethtown and Lee Creek Mine, one of the most extensively studied North Carolina Pliocene sites, were compared. Assemblages were extremely dissimilar (percentage similarity measurement of 3.3%). Modern distributions of M. undulatus and L. aff. L. xanthurus are very strong indicators of shallow, soft bottom estuarine creeks and bays. The preponderance of juvenile M. undulatus (99.5% represent 1-year-old or less) is a strong indicator for a primary nursery area. This specialised habitat explains the dominance of juvenile Atlantic croakers and spots, the high percentage of fishes distributed in freshwater, brackish, and marine environments, and the paucity of marine-only species. The specialised habitat indicated at Elizabethtown would also account for the pronounced difference between the Elizabethtown and Lee Creek otolith assemblages.