Fish Surveys Research Articles

Effect of environmental DNA sampling resolution in detecting nearshore fish biodiversity compared to capture surveys.

Sampling and sequencing marine environmental DNA (eDNA) provides a tool that can increase our ability to monitor biodiversity, but movement and mixing of eDNA after release from organisms before collection could affect our inference of species distributions. To assess how conditions at differing spatial scales influence the inferred species richness and compositional turnover, we conducted a paired eDNA metabarcoding and capture (beach seining) survey of fishes on the coast of British Columbia. We found more taxa were typically detected using eDNA compared to beach seining. eDNA identified more taxa with alternative habitat preferences, and this richness difference was greater in areas of high seawater movement, suggesting eDNA has a larger spatial grain influenced by water motion. By contrast, we found that eDNA consistently missed low biomass species present in seining surveys. Spatial turnover of communities surveyed using beach seining differed from that of the eDNA and was better explained by factors that vary at small (10-1000s meters) spatial scales. Specifically, vegetation cover and shoreline exposure explained most species turnover from seining, while eDNA turnover was not explained by those factors and showed a distance decay pattern (a change from 10% to 25% similarity from 2 km to 10 km of distance), suggesting unmeasured environmental variation at larger scales drives its turnover. Our findings indicate that the eDNA sample grain is larger than that of capture surveys. Whereas seining can detect differences in fish distributions at scales of 10s-100s of meters, eDNA can best summarize fish biodiversity at larger scales possibly more relevant to regional biodiversity assessments.

Optimizing landscape-scale coastal monitoring and reporting through predicted versus observed animal abundance models

Abstract Effective environmental management hinges on monitoring drivers of change and effectively communicating results to stakeholders. While animals are valuable for engagement, few monitoring programs successfully integrate metrics quantifying their assemblages. We studied fish responses to environmental factors (including landscape context and water quality) in a 3-year survey across six ecosystems and 13 estuaries in eastern Australia (for >1800 fish surveys), and developed a novel predicted versus observed approach to monitoring, grading, and reporting on animal populations. Fish species richness and the abundance of five indicator species were explained significantly by at least one spatial attribute of sites (e.g. connectivity with mangroves and the ocean), and at least one water quality metric reflecting annual median water conditions (especially turbidity, dissolved oxygen (DO), and chlorophyll a concentration). For our grading approaches, predicted values were calculated for each replicate using best-fit models for each indicator, thereby accounting for natural spatiotemporal variation and standardizing site-to-site comparisons. Evaluating six methods for translating values into graded scores for each estuary, we recommend a simple metric: the percentage of sites with observed values above predictions. We discuss this approach as useful and complementary to programs with predominantly physical parameter monitoring, and discuss challenges in establishing ongoing protocols.

Pressures on Egyptian Red Sea fisheries from the artisan fishers’ perspective

The Egyptian Red Sea (ERS) supports artisanal, commercial and recreational fisheries, managed using a summertime closure, not applied to recreational fishing. Stock status is little known and management options are severely limited. To inform future management, we report the results of a questionnaire survey of artisan fishers from four Red Sea ports, collecting basic socioeconomic and fisheries data: fleet characteristics, self-reported landings, plus attitudes towards current management. Relationships among catches, technical and social categories and categorised attitudes were analysed using ordinal and multinomial logistic regressions. Median income of ERS artisanal fishers was 54% of the mean income from work in rural Egypt in 2020. Almost all respondents reported declining catches (61% blamed “overfishing”) and most were pessimistic (43% expected to remain fishing in 10 years time). The seasonal closure was poorly supported by artisanal fishers: 75% claimed it contributed to declining resources. The timing of the closure, intended to protect spawning fish, aligned with published spawning seasons for some, but not all important species. 66% of fishers identified this mismatch as the reason for policy failure. High dissatisfaction rates risk non-compliance: e.g. 23% of those interviewed switched to ‘recreational’ fishing during the closed season. Most artisan fishers of the ERS are in a precarious economic position, facing a declining resource, under management that few support, with concerns about the long term future for their livelihood. We suggest transition to a participatory approach with data-driven co-management as a long term solution.

Fish Diversity of East Sea Streams in Nakdong River Region

Fish surveys were conducted near artificial structures installed in eight streams flowing from the Nakdong River region to the east coast of Korea. As a result of the survey, a total of 20,000 individuals belonging to nine orders, 17 families, and 47 species were found. The dominant species was Zacco koreanus, and the subdominant species was Pungtungia herzi. Among the surveyed fish species, endangered species were Pseudobagrus brevicorpus (rank I) and Cottus hangiongensis (rank II). In addition, migratory fish species were Oncorhynchus keta, Plecoglossus altivelis, and Tribolodon hakonensis. As a result of community analysis, the highest diversity, dominance, richness, and evenness indices were Wangpi, Chuksan, Gokgang, and Janggi Stream respectively. The highest number of species was surveyed in Gokgang Stream (25 species). Alpha diversity, the number of species at each survey point in each stream, was the highest at a survey point in Wangpi Stream (20 species), and beta diversity, species at each stream survey point that does not overlap with nearby survey point, was the highest at survey points in Gokgang Stream (12 species). As a result of the similarity analysis, surveyed streams were divided into four groups: group 1 (Chuksan, Baeknok Stream), group 2 (Uljinnamdae, Wangpi, Yungdeokosip Steam), group 3 (Gokgang Stream), and group 4 (Janggi, Hoeya Stream). This study is expected to serve as basic data for managing the aquatic ecosystem of streams flowing from the Nakdong River region to the east coast.

Biodiversity conservation and restoration of wetlands in suburban areas: challenges and prospects

Context Wetland loss threatens global biodiversity. Peri-urban wetlands face acute pressures from urban expansion. Aims Investigate biodiversity and land-cover changes in two wetlands undergoing suburbanisation near Hangzhou, China. Methods Seasonal field surveys of birds, fish and amphibians, coupled with remote-sensing analysis of land-cover changes from 2009 to 2020. Key results Suburban wetlands exhibited unique degradation patterns, including reduced species diversity, simplified community structures and proliferation of invasive species, with 91 bird species being recorded, dominated by common residents, 25 still-water fish species with few carnivores and migratory species, and 5 ubiquitous amphibian species detected. Species richness was lower than in nearby conserved wetlands. From 2009 to 2020, 6–7% of the wetlands were lost to urban expansion and converted to artificial vegetation or infrastructure. Conclusions Ecological degradation is driven by rapid urbanisation, with habitats being fragmented by roads and converted to artificial land covers. Water pollution from insufficient treatment and abandoned aquaculture further impairs habitats. Implications Innovative integrated-management framework was proposed for wetlands biodiversity restoration in suburban area. Key strategies include (1) modernising traditional circular economies to sustain wise use, (2) wildlife-friendly infrastructure design, (3) targeted invasive species control, and (4) adaptive co-management informed by ongoing monitoring. This socio-ecological systems approach aims to harmonise biodiversity conservation, cultural heritage and sustainable development in threatened suburban wetlands.

Taxonomic Diversity and Interannual Variation of Fish in the Lagoon of Meiji Reef (Mischief Reef), South China Sea.

Coral reef fish are important groups of coral reefs, which have great economic and ecological value. Meiji Reef is a representative tropical semi-enclosed atoll in the South China Sea, with rich fish resources. Based on the data from hand-fishing, line-fishing, and gillnet surveys of fish in Meiji Reef from 1998 to 2018, this study summarized the fish species list of Meiji Reef and analyzed the species composition, inclusion index at the taxonomic level (TINCL), genus-family diversity index (G-F index), average taxonomic distinctness index (Δ+), and variation in taxonomic distinctness (Λ+) and their changes. The results revealed that from 1998 to 2018, there were 166 reef-dwelling fish species on Meiji Reef, belonging to 69 genera, 33 families, and 11 orders, of which 128 species were from 20 families of Perciformes, accounting for 77.10% of the total cataloged species. Regarding the dependence of fish on coral reefs, there were 155 reef-dependent species or resident species (accounting for 93.37%) and 11 reef-independent species or wandering species (accounting for 6.63%). The TINCL of the order, families, and genus of fish in Meiji Reef were very high. The genus diversity index (G index), family diversity index (F index), and G-F index of fish in Meiji Reef were very high, and the G index of fish in Meiji Reef in 1998-1999 was higher than that in 2016-2018. The Δ+ and Λ+ values of fish in Meiji Reef from 1998 to 2018 were 56.1 and 148.5, respectively. Compared with 1998-1999, Δ+ and Λ+ of fish increased during 2016-2018, reflecting that the relatives of fish in Meiji Reef became further distant, and the uniformity of taxonomic relationships among species decreased. The research findings indicated that fish exhibited a high taxonomic diversity in Meiji Reef; however, it also revealed significant fluctuations in the fish diversity of Meiji Reef over an extended period, emphasizing the urgent need for timely protection measures. This investigation significantly contributes to our comprehension of the intricate dynamics governing fish species within Meiji Reef and holds broader implications for biodiversity conservation in tropical marine ecosystems.

Diversity, functional redundancy, and vulnerability of reef fish communities of the Saudi Arabian coast, in the northern Red Sea

In light of the current development of several giga-projects along the Saudi Red Sea coast, understanding the health status of coral reefs is paramount to developing baselines and management strategies to minimize the human impact on these ecosystems. Here, we present an assessment of the diversity, functional redundancy, and vulnerability for coral reef fish communities in the northern Red Sea. The focus area of our study falls within the marine jurisdiction of the NEOM giga-project. We performed fish surveys with three different methods aiming to cover a wide set of habitats and thus capture a comprehensive picture of the regional diversity: i) standardized belt transects, ii) roving diviersity surveys, and iii) collection of cryptobenthic fish. Our results showed a highly variable community composition along the ten surveyed sites highlighting Sindalah as an essential site for piscivore species, Al Muwaileh as an important site for herbivores, and Sanafir-Tiran as the most diverse site. Functional diversity analysis revealed similar levels of redundancy, over-redundancy, and vulnerability among sites. Functional richness, evenness, and divergence did not vary substantially between sites and, in general, indicated that the fish communities in the selected sites present mid to low levels of functional diversity. We further compare regional-scale and site-specific functional assessments. Notably, some of the species groups that are functionally redundant at the regional scale represented vulnerable functions at the site level. These results call to attention the need to create site-specific conservation strategies and not to solely rely on regional diviersity assessments as the basis for management decisions.

Coral reef recovery in a remote and large marine protected area is resilient to cascading trophic interactions

Large marine protected areas (MPAs) will likely multiply worldwide to address accelerating biodiversity loss. Coral reefs are an especially at-risk ecosystem, but our understanding of whether and how large MPAs will benefit reef recovery from disturbances remains limited. Here, we evaluate how fishes influence coral reef recovery and if there are cascading trophic interactions in the fish community that influence recovery. We combine i) a meta-analysis of previous research evaluating how fishes affect coral reef succession, ii) field surveys of sharks, fishes, and benthic cover, and iii) a 2.5-year coral recruitment experiment of caged, uncaged, and partially caged settlement tiles in a remote and large MPA, in the Chagos Archipelago. In both our meta-analysis and field experiment, we found variable effects of fishes on coral recruitment with no overall significant effect, but strong control by fishes on the developing benthic communities, where fishes promote crustose coralline algae and reduce macroalgae. Within the Chagos, fishes had a positive effect on corals in protected microhabitats but a negative effect on exposed surfaces, leading to an overall neutral effect from fishes. Although mesopredatory fish abundance was negatively correlated with shark abundance, these top-down effects did not cascade down the food web through herbivores and corallivores to coral recruitment and benthic succession. Thus, our results suggest that within this large MPA, herbivores are important in limiting algae during recovery and there are compensatory responses to the loss of benthic feeding fishes and sharks, with implications for coral reef persistence in the face of global change.

БОЛЕЗНИ ПРОХОДНЫХ ЛОСОСЁВЫХ РЫБ ПРИ ИСКУССТВЕННОМ ВОСПРОИЗВОДСТВЕ В УСЛОВИЯХ КРАЙНЕГО СЕВЕРА ДАЛЬНЕГО ВОСТОКА

Replenishment of fish stocks by increasing the release of juveniles during artificial fish farming is currently an urgent problem in the Far North of the Far East. In 1995-2003; 2021, an epizootological survey of natural spawning grounds and fish farming enterprises located in the northern part of the Okhotsk Sea basin was conducted: Ola, Arman, Taui, Yana, Iret, Ola experimental production acclimatization base, Armansky, Taui, Yansky salmon hatcheries. The aim is to study bacterial and protozoal diseases of passing salmonids in artificial fish farming. The novelty of the research is that for the first time in the waters of the northern part of the Okhotsk Sea basin, bacterial and parasitic diseases were detected in passing salmon fish in natural reservoirs during anadromous migration and artificial fish farming. In pink salmon, chum salmon, coho salmon, sockeye salmon, Aeromonas hydrophila culture isolated from blood and internal organs turned out to be virulent. Aeromonosis was established for the first time in passing salmon fish of natural populations. As a result of bacteriological studies, Aeromonas hydrophila bacteria were isolated from different batches of fertilized eggs, yolk sac of larvae, ascitic fluid of the abdominal cavity of juveniles. Due to the detection of the invasion of juvenile fish Trichodina truttae and Myxosoma cerebralis, which amounted to 10.0-46.5%, trichodyniosis and myxosomiasis were registered. The ways of transmission of infection to fish farms have been established. Fertilized eggs are infected from producers on spawning rivers during the selection of sexual products. The epizootological situation of aeromonosis, trichodyniosis and myxozomiasis is recognized as unfavorable. The method of diagnosis of bacterial diseases of salmonids at fish-breeding enterprises of the region has been improved.

Vertical structure of Caribbean deep-reef fishes from the altiphotic to deep-sea boundary

While recent technical breakthroughs have enabled advances in the description of reefs down to 150 m, the structure and depth zonation of deep-reef communities below 150 m remains largely unknown. Here, we present results from over 10 years of deep-reef fish surveys using human-occupied submersibles at four locations across the Caribbean Sea, constituting one of the only continuous reef-fish surveys from 10 to 480 m (1 site) and 40 to 300 m (3 sites). We identify four vertically stratified deep-reef fish communities between 40 and 300 m bordered by an altiphotic (0–10 m) and a deep-sea (300–480 m) community. We found a strong faunal break around 150 m that separates mesophotic and rariphotic zones and secondary breaks at ~ 70 to 90 m and ~ 180 to 200 m subdividing these zones into upper and lower communities. From 300 to 480 m in Roatán, we found a single fish community dominated by deep-sea families, indicating that the lower boundary of the reef-fish realm occurs at 300 m. No differences were found between communities ranging from 20 to 60 m, suggesting that fishes from the lower altiphotic and upper mesophotic form an ecological continuum. While some variability was observed across sites, the overall depth zonation and key species characterizing depth zones were consistent. Most deep-reef species observed were depth specialists restricted to a single depth zone, but many shallow-reef species extended down to mesophotic depths. Depth segregation among species of a genus was found across ten reef-fish genera and likely constitutes one of the mechanisms driving community distinctiveness and thereby fish diversity across depths.

Environment DNA Reveals Fish Diversity in a Canyon River within the Upper Pearl River Drainage.

Investigating fish diversity in canyon rivers through conventional fish surveys is challenging due to precipitous conditions, including steep slopes, rapid water flow, and complex habitats. Additionally, intensive construction of dams has further complicated the understanding of contemporary fish diversity in these rivers. In this study, we used the environmental DNA (eDNA) technique to assess fish diversity and examine the effects of dams on fish diversity in the Mabiehe River, a canyon river in the upper reaches of the Pearl River drainage. Water samples from 15 sampling sites were collected, yielding 9,356,148 valid sequences. Utilizing the NCBI public database, a total of 60 freshwater fish species were identified, with Carassius auratus, Cyprinus carpio, and Pelteobagrus fulvidraco being the most dominant species in the Mabiehe River. We also detected one nationally protected fish species, three provincially protected fish species, and six exotic species in this river. Furthermore, eDNA analyses demonstrated that the lotic river sections harbor more species and greater diversity than dammed sections, suggesting that dams might exert significant impacts on local fish diversity. Overall, this study supports the effectiveness of the eDNA technique as a complementary tool to traditional field surveys for monitoring fish biodiversity in canyon rivers.

Morphological and molecular identification of metacestodes infecting teleost fishes of Moreton Bay, Australia

In a parasitological survey of fishes from Moreton Bay (southeastern Queensland, Australia), 169 teleost fishes, representing 54 species from 28 families, were examined for larval cestodes. Of these 54 species, 36 were found to be infected by metacestodes. Metacestodes were characterised by morphological and molecular data (the D1-D3 region of the 28S rDNA gene); these data were analysed in parallel to inform larval type allocation. Metacestodes collected represented eight morphological types, seven previously reported (Types I, II, IV, V, VI, VII, and X) and one novel type (Type XVI). Phylogenetic analyses were conducted to genetically match larval types to adult cestodes. Six of the eight larval types found were matched to adult forms: Type I metacestodes matched species of Phoreiobothrium Linton, 1889 (Onchobothriidae); Type II metacestodes matched species of Acanthobothrium van Beneden, 1849 (Onchobothriidae); Type IV metacestodes matched species of Scyphophyllidium Woodland, 1927 and Alexandercestus Ruhnke & Workman, 2013 (Phyllobothriidae); Type VI metacestodes matched species of Anthobothrium van Beneden, 1850 (Tetraphyllidea incertae sedis); Type X metacestodes matched species of Ambitalveolus Caira & Jensen, 2022 (Tetraphyllidea incertae sedis); and Type XVI metacestodes matched species of Platybothrium Linton, 1890 (Onchobothriidae). Based on phylogenetic topology, Type V metacestodes are inferred to match Pedibothrium Linton, 1909 (Balanobothriidae) and Type VII metacestodes are inferred to match Spongiobothrium Linton, 1889 (Rhinebothriidae). These findings support and extend the unified morphological type system proposed previously, but suggest that morphological types will ultimately be informative to identify metacestodes to a group of related genera rather than any distinct genus.

Small pelagic fish: new frontiers in science and sustainable management

Small pelagic fishes occupy an important trophic role in every global aquatic ecosystem, and many species are heavily exploited by fisheries, including some of the largest and most valuable capture fisheries in the world. In November 2022, a symposium on small pelagic fish titled “ Small Pelagic Fish: New Frontiers in Science and Sustainable Management” was cohosted by PICES, ICES, and FAO in Lisbon, Portugal. This special issue contains a collection of research manuscripts that explore approaches currently being used and developed to assess and manage small pelagic fishes. In particular, this issue covers topics on novel approaches to surveying small pelagic fishes, incorporating environmental covariates into management, management strategy evaluation, and aspects of the economics of small pelagic fisheries. The conclusions highlight the importance of new approaches that seek to enhance small pelagic fish surveys and ecosystem monitoring, incorporate that ecosystem information into management strategy evaluation, and predict the potential impacts of ecosystem changes on outcomes for economies and communities that rely on sustainable populations of small pelagic fishes.

Anthropogenic and environmental drivers of Acanthurus achilles presence in Hawai‘i

Despite the ecological and social importance of reef fishes, data on their populations, habitat use, and other drivers are often scarce, which creates challenges for effective management. These challenges are particularly acute for rare or at-risk species such as Acanthurus achilles, a reef fish with a documented population decline in recent years in Hawai‘i, USA. We used a data set of in situ fish surveys from across the main Hawaiian Islands combined from multiple survey programs to quantify A. achilles presence and absence and applied generalized linear mixed-effects models to examine the relationships between presence of (1) all individuals, (2) juveniles, and (3) adults with 27 spatially continuous environmental and anthropogenic drivers to understand the main drivers of presence. Using the modeled relationships between presence and all drivers, we predicted the probability of A. achilles presence at a 100 m scale within the 30 m depth contour of the main Hawaiian Islands. Environmental drivers, especially habitat drivers such as depth and rugosity, emerged as significant drivers of A. achilles presence, while anthropogenic drivers like land-based pollution and fishing had fewer significant relationships with A. achilles presence. The predicted probability of presence varied both between islands as well as within islands, with the highest probability of presence around Kaho‘olawe and Hawai‘i and the lowest around O‘ahu. Our modeling approach and high-resolution spatial predictions provide empirical evidence of the importance of environmental drivers in explaining A. achilles presence and identify preferred habitat at relevant scales for fisheries management.

Identifying fish and estimating abundance and swim velocities of migrating Pacific salmon using adaptive resolution imaging sonar in mobile surveys

Abstract Mobile acoustic sounding is an effective survey method for fish abundance residing or migrating in large riverine basins and marine areas. A long-standing challenge in acoustic fish surveys with conventional sonar is the uncertainty in identifying fish targets from acquired echo data. Identification errors of fish targets can significantly bias estimates of fish abundances and negatively impact the management of fisheries. In contrast to conventional sonar, adaptive resolution imaging sonar (ARIS), if deployed properly with appropriate settings, can yield high-quality images of fish targets. ARIS images acquired with adequate frame rates can form video recordings to allow for confident identification of fish targets from recorded morphological features, sizes, direction of movements, and speeds. In this paper, we present an approach of using ARIS sonar for mobile surveys of fish passage in a riverine environment. Applications of this approach are demonstrated for its practical values with results from an ARIS-based mobile survey of upstream migrating salmon at an acoustically challenging fish-counting site on the lower Fraser River in British Columbia, Canada.

Different patterns of coupled predator-prey dynamics when the same species interact in different locations.

Individual predator and prey species exhibit coupled population dynamics in simple laboratory systems and simple natural communities. It is unclear how often such pairwise coupling occurs in more complex communities, in which an individual predator species might feed on several prey species and an individual prey species might be attacked by several predators. To examine this problem, we applied multivariate autoregressive state-space (MARSS) models to 5-year time-series of monthly surveys of a predatory fish, the eastern mosquitofish (Gambusia holbrooki), and its littoral zone prey species, the least killifish (Heterandria formosa), in three locations in north Florida. The MARSS models were consistent with coupled predator-prey dynamics at two of the three locations. In one of these two locations, the estimated densities of the two species displayed classic predator-prey oscillations. In the third location, there was a positive effect of killifish density on mosquitofish density but no detectable effect of mosquitofish density on killifish density. In all three locations, increased submergent vegetation cover was associated with increased prey density but not increased predator density. Eigenvalues analyses for the joint predator-prey dynamics indicated that one of the cyclic locations had more stable dynamics than the other locations. The three different patterns demonstrate that the dynamics of a pairwise predator-prey interaction emerge not only from the characteristics of the prey and the predator, but also those of the habitat and trophic web in which the predator and prey are embedded.

Survey of Iced Fishes Sold in Makurdi Metropolitan

Survey of Iced Fishes Sold in Makurdi Metropolitan

Reconstructing historical fish occurrence and documenting human-mediated introductions in lakes using sedimentary DNA

The recovery of DNA preserved in the sediment of aquatic systems (sedDNA) has provided short-term and long-term data on biological groups (e.g., bacteria, phytoplankton, zooplankton, and fishes) and has advanced our understanding of how environmental changes have affected aquatic communities. Here, we demonstrate the use of fish sedDNA from lake sediment cores in reconstructing the history of fish occurrences in four lakes within the Oil Sands region in Alberta, Canada. A general fish and eight targeted qPCR-based eDNA assays for freshwater fish species (cisco, lake whitefish, northern pike, chain pickerel, burbot, rainbow trout, lake trout, and walleye) were rigorously designed and validated. Utilizing these assays, we detected sedDNA from several fish species in sediment cores spanning over a century, which aligned with conventional fish surveys and historical records of human-mediated introductions. The use of fish sedDNA provided greater temporal resolution into the historical fish faunal records, bridging the knowledge gap that spanned from 100- to 150-year-old data. The present study also allowed documentation of human-mediated introductions of fish populations to the examined lakes. These findings can be used to refine native freshwater fish ranges and clarify the influence of human-mediated introductions on fish diversity in lakes, providing essential baseline data for conservation management and environmental impact assessments.

A New Workflow for Instance Segmentation of Fish with YOLO

The application of deep-learning technology for marine fishery resource investigation is still in its infancy stage. In this study, we applied YOLOv5 and YOLOv8 methods to identify and segment fish in the seabed. Our results show that both methods could achieve superior performance in the segmentation task of the DeepFish dataset. We also expanded the labeling of specific fish species classification tags on the basis of the original semantic segmentation dataset of DeepFish and completed the multi-class instance segmentation task of fish based on the newly labeled tags. Based on the above two achievements, we propose a general and flexible self-iterative fish identification and segmentation standard workflow that can effectively improve the efficiency of fish surveys.

Contemporary Trends in the Spatial Extent of Common Riverine Fish Species in Australia’s Murray–Darling Basin

As one of the world’s most regulated river basins, the semi-arid Murray–Darling Basin (MDB) in south-eastern Australia is considered at high ecological risk, with substantial declines in native fish populations already identified and climate change threats looming. This places great importance on the collection and use of data to document population trends over large spatial extents, inform management decisions, and provide baselines from which change can be measured. We used two medium-term data sets (10 MDB basin-wide fish surveys from 2004–2022) covering the 23 catchments and 68 sub-catchments of the MDB to investigate trends in the distribution of common riverine species at the entire basin scale. Fifteen native species were analysed for changes in their contemporary range, and whilst short-term changes were identified, all species showed no significant continuous trend over the study period. We further analysed the native species extent relative to their historic records, with bony herring and golden perch occurring in 78% and 68% of their historic river kilometres, respectively, whereas southern pygmy perch, northern river blackfish, silver perch, mountain galaxias, and freshwater catfish were all estimated to occur in less than 10% of their historic extent. Six established non-native species were also analysed and were very consistent in extent over the years, suggesting that they are near the available limits of expansion of their invasion. We provide effect sizes for the spatial extent index which can be used as baselines for future studies, especially those aiming to monitor changes in the spatial extent and population status of native species, or changes in the spatial extent of new or existing non-native species.