Changes In Fish Assemblages Research Articles

Contrasted spatio-temporal changes in the demersal fish assemblages and the dominance of the environment vs fishing pressure, in the Bay of Biscay and Celtic Sea

Climate change and resource exploitation represent strong selection pressure affecting the spatio-temporal dynamics of marine assemblages that ensure food provision for humans. However, such dynamics remain poorly documented, and their drivers unclear. Here, we investigate changes in fish assemblages of two key European fishing areas, the Bay of Biscay (BoB) and the Celtic Sea (CS), during the last two decades. We quantify the relative contribution of change in energy (i.e. temperature and trophic resources), habitat (depth, substrate, oxygen) and fishing pressure to explaining observed spatial and temporal variations in fish diversity. We used long-term scientific surveys to evaluate the spatio-temporal changes in species richness (SR), abundance and composition of demersal fish (Actinopterygii) assemblages at different spatial scales combined with a range of regression models and variance partitioning. Diversity patterns showed greater variability in space than in time: SR weakly changed over time, while compositional dissimilarity showed local patterns of taxonomic homogenization in the CS and differentiation in the southern BoB, where local assemblages were becoming more similar and dissimilar over time, respectively. Energy funnelled through small pelagic species as a potential trophic link affecting the dynamics of demersal assemblages was the most important driver, while habitat and fishing pressure had limited importance. Our study revealed contrasted dynamics of demersal fish assemblages at a regional scale that were best explained by the dynamics of small pelagic species. Direct effects of environmental forcing and fishing pressure were limited in both regions which have a long history of fishing and still remain relatively buffered from global warming effects. This research paved the way to combine methods inspired by biogeography with scientific monitoring surveys to detect spatio-temporal dynamics of fish assemblages and their drivers in marine ecosystems under multiple pressures.

Influence of climate change and extreme weather events on an estuarine fish community

Extreme weather events are becoming more frequent as a result of climate change, and the increasing frequency of these events may lead to significant changes in fish assemblages. In this sense, this work aimed to study the effects of climate change and extreme weather events on fish assemblages in the Rio Minho estuary (Portugal). Between 2010 and 2019, continuous weekly sampling with fyke nets was carried out to assess the dynamics of fish assemblages in the estuary. In addition, temperature and precipitation data were obtained from satellite information to assess the relationship between climatic variables and fish composition, structure, and diversity. Fish populations changed significantly over time, becoming less diverse and largely dominated by a few, mostly invasive species (e.g., carp, goldfish, pumpkinseed, and tench), while the abundance of most native species declined over the years (e.g., panjorca, stickleback, and shad). High temperatures and low precipitation negatively affected native species, while the invasive species benefited from increased temperatures and extreme weather events (droughts and floods).

Spatial and Temporal Variations in Fish Assemblage in Feitsui Reservoir, in Northern Taiwan, from 2006–2020

Reservoirs are artificial ecosystems that modify the hydrological and environmental components nearby. The long-term monitoring of fish assemblages in reservoirs may provide key information to understand how these artificial ecosystems allow fish population fluctuations and identify proper conservation strategies. A sentinel-site approach method assessed changes in fish assemblages in the Feitsui Reservoir (1024 ha) over 14 years, including the periods 2006–2008, 2010–2011, 2016, 2018, and 2020. Fish assemblages, sampled using gill nets, were composed of 38 species (12 families and 8 orders) with Cyprinidae as the dominant family; the fish fauna were dominated by species of the family Cyprinidae (71%) and Cichlidae (20.3%). Principal component analysis and nonmetric multidimensional scaling categorized the assemblages into two groups (cold and warm seasons), and we identified three parameters that were significantly correlated with the season (p < 0.05): SD (R = −0.04), Chl-a (R = 0.01), and algal count (R = 0.19); the algal count was higher in the warm season than in the cold season. The fish assemblage in the cold and warm seasons contained no exclusive taxa, contributing to the dissimilarity between the groups. The fish assemblage for the years before and after 2010 indicated partial overlap between the two groups; S. macrops contributed greatly to the separation of the two periods (>10% each; SIMPER) and O. mossambicus was dominant in assemblage structures after 2010. Our findings show the importance of long-term fish monitoring for the investigation of the effects of nonnative fish species on native fish species composition.

Changes in fish assemblages after marine heatwave events in West Hawai‘i Island

Marine heatwaves are prolonged events of anomalously warm water that affect diverse marine habitats and their associated biota. Evidence shows that anthropogenic climate change is increasing the frequency and duration of marine heatwaves and that coral reef systems are sensitive to the thermal stress imposed by these heatwaves. In this study, we examined fish community response to consecutive marine heatwaves (2014-2015) by analyzing changes in fish assemblages in Hawai‘i over 11 yr (2009-2019). Subtidal video survey data were collected in 3 areas on the west side of the Big Island of Hawai‘i. Fish were counted and identified to species or genus, then assigned to one of 7 functional groups: predators, secondary consumers, planktivores, corallivores, scrapers, grazers or browsers. Our study revealed 4 key findings. We show that all fish assemblages changed significantly in each area after the marine heatwaves. Across all 3 areas, the 3 most abundant functional groups (planktivores, grazers and secondary consumers) drove the observed changes in the community. Following the marine heatwaves, fish abundance increased in 2 areas with fewer fishing regulations. In the most protected area, fish abundance remained high and diversity indices were significantly higher post-marine heatwaves. Our results support the hypothesis that marine heatwaves can cause shifts in fish assemblages and that the precise nature of these shifts can vary over relatively short spatial scales that may coincide with scales of management.

Dam failure and mammals

Brazil experienced the largest socioenvironmental catastrophe of its history, caused by a tailings dam failure, known as “Mariana disaster”. The wave of iron-mining waste buried villages, contaminated the Doce River, and left an immense ocean plume. The Doce River watershed is the largest in southeast Brazil, and located in the Atlantic Forest domain, presenting an outstanding economic, social, and biological relevance. Although the effects of such tragic events are usually assessed through fish assemblage changes, mammals have important effects on environment structure and regeneration. Inventories are of prime importance for adequate conservation efforts as well as for evaluating impacts of any disaster. Therefore, the aim of this paper was to present an updated assessment of mammalian list collected in the affected portion of Doce River before the dam failure therefore contributing to future conservation efforts. Data collection comprised specimens deposited in Museu Nacional/UFRJ, the oldest mammal collection of Brazil, and literature review. The two surveys together retrieved 157 species from 31 families and 11 orders, representing around 60% of the known mammalian diversity in the Atlantic Forest, including some in critical conservation condition, such as the Franciscana dolphin, the northern muriqui and the giant otter. Mining is a byproduct of present society, with dam breaches as a recurring problem. Facing the importance of Doce River to both Brazilian biodiversity and society, the chain of events must be taken into account in environmental rehabilitation strategies, and taxa less commonly assessed, like mammals, should be included.

Long-term changes in reef fish assemblages after 40 years of no-take marine reserve protection

Marine reserves can increase the abundance and size of harvested fish species, but the indirect effects of protection on wider fish assemblages are less well understood. Better understanding how marine reserves indirectly effect reef fish is essential to interpreting changes in non-targeted taxa and informing management expectations as to the long-term effects of marine protection. We investigated how reef fish assemblages and habitats have changed within New Zealand's oldest marine reserve after 40 years of no-take protection (1978 to 2018), and how they differed inside and outside the reserve in 2018. Reef fish assemblages differed between 1978 and 2018, and between reserve and fished sites, and these effects were greatest at depths where habitats had changed. We report an overall increase in fish biomass in the reserve, but a long-term decline in total fish density. The increase in biomass under protection was largely driven by an increase in six target species. Eleven species exhibited long-term declines in the marine reserve; three likely a result of indirect effects related to habitat change and/or increased predation, while other declines likely reflect large-scale changes independent of reserve protection. Predicted indirect effects associated with large-scale habitat change were not apparent, except for an increase in one non-target herbivore species alongside increased kelp abundance. While further work is needed to confirm the mechanisms driving individual indirect effects, the results demonstrate that the long-term indirect effects of protection on reef fish are less common, more complex and more difficult to predict than direct effects.

Long-term changes in temperate marine fish assemblages are driven by a small subset of species.

The species composition of plant and animal assemblages across the globe has changed substantially over the past century. How do the dynamics of individual species cause this change? We classified species into seven unique categories of temporal dynamics based on the ordered sequence of presences and absences that each species contributes to an assemblage time series. We applied this framework to 14,434 species trajectories comprising 280 assemblages of temperate marine fishes surveyed annually for 20 or more years. Although 90% of the assemblages diverged in species composition from the baseline year, this compositional change was largely driven by only 8% of the species' trajectories. Quantifying the reorganization of assemblages based on species shared temporal dynamics should facilitate the task of monitoring and restoring biodiversity. We suggest ways in which our framework could provide informative measures of compositional change, as well as leverage future research on pattern and process in ecological systems.

Two-Year Cycle of Vendace (Coregonus albula) in Pyhäjärvi, SW Finland: Evidence for Asymmetric Competition Between Adults and Juveniles

Long-term monitoring of the planktivorous vendace (Coregonus albula) in Pyhäjärvi, a lake in SW Finland, revealed periods characterised by different types of population regulation. In 1971–1989, the vendace stock was strong and exhibited a two-year cycle. In 1990–1999, extreme weather conditions and predation resulted in recruitment failures, after which overfishing kept year-classes small. From 2000 onwards, the two-year oscillations were re-established at a lower level. Here, we show that the two-year cyclicity prevalent in the 1980s was consistent with the hypothesis of asymmetric competition between adults and juveniles. Food consumption by juveniles of strong year-classes retarded growth and weakened condition of the co-occurring adults, resulting in less abundant year-classes. In 2000–2018, the role of intraspecific competition diminished due to interspecific competition from increased populations of other planktivorous fish, preventing vendace from attaining higher abundance. Elevated temperature probably confounded the effects of competition, but its direct role was masked by simultaneous gradual eutrophication and fish assemblage changes.

Response of estuarine fishes to elevated temperatures within temperate Australia: Implications of climate change on fish growth and foraging performance

Range shifts of marine fishes are well documented to respond to climate change, however the physiological mechanisms linked to these shifts are poorly understood. Responses of estuarine fishes, which have limited scope to shift, are particularly lacking. We tested the influence of present (18 °C, 22 °C) and predicted near-future (26 °C) water temperature on the growth and foraging performance of five common co-occurring fish: eastern trumpeter Pelates sexlineatus (Quoy & Gaimard 1824), eastern fortescue Centropogon australis (White 1790), yellowfin bream Acanthopagrus australis (Owen, 1853), fan-belly leatherjacket Monacanthus chinensis (Isbeck 1765), bridled leatherjacket Acanthaluteres spilomelanurus (Quoy & Gaimard 1824), from an urbanised, temperate estuary near Sydney. Growth performance was quantified as instantaneous growth rate over a two-week period, whilst foraging performance was assessed on bite rate, time to feeding, boldness and also escape response. Growth patterns were significantly species-specific, and all species except for M. chinensis (high within-treatment variance) exhibited significant growth differences among the temperature treatments. The growth of P. sexlineatus and A. australis increased with temperature, A. spilomelanurus lost weight with temperature and C. australis exhibited a hump-shaped performance curve with the highest growth occurring at 22 °C. Bite rate, boldness, and escape response increased, and time to feeding decreased with higher water temperature in P. sexlineatus, A. australis and M. chinensis. Surprisingly, there was no significant association between these foraging characteristics and growth rate of individuals within each temperature treatment. This study validates the hypothesis that species within temperate estuaries will be significantly, and differently, affected by the isolated impact of water temperature rise, culminating in changes in local fish assemblages. These changes may include shifts in species dominance, trophic interactions, and migration, as well as changes to the productivity of fisheries that rely on these populations.

Spatial and seasonal patterns of the surf-zone ichthyofauna on a tropical Atlantic dissipative coastline

The surf-zone of twelve sandy beaches on a tropical Atlantic dissipative coastline (Sergipe, Brazil) was studied to assess whether fish assemblages may be affected by spatial (proximity to estuaries) and seasonal (wet vs. dry) variations. Sampling locations were classified into sites of greater estuarine (EC) and marine (MC) contribution according to the coastal geomorphology. Samples were obtained by beach seining, and selected environmental variables including distance from estuarine mouths were recorded for each location. A total of 2134 fishes belonging to 21 families and 33 species were collected. The eight most abundant species were Mugil liza, Anchoa januaria, Polydactylus virginicus, Atherinella brasiliensis, Caranx latus, Trachinotus carolinus, Menticirrhus littoralis, and Trachinotus goodei. Species abundance varied significantly between sites and seasons, and taxonomic distinctness only between sites. Distance from estuaries, water salinity and temperature, and rainfall were the best predictors of the spatial and seasonal changes of fish assemblages in the surf-zone of tropical Atlantic dissipative sandy beaches. The occurrence of juveniles and recruits from most of the species recorded supports the nursery habitat hypothesis of shallow surf-zones.

Fish biodiversity and assemblages along the altitudinal gradients of tropical mountainous forest streams

Knowledge of the fundamental aspects of ecology such as the patterns of fish species distribution and biodiversity in the forest streams is the first and basic step to develop effective conservation strategies. Yet, studies on altitudinal changes of fish composition and assemblages in Bornean forest streams are scarce despite being one of the hotspots of biodiversity conservation. Hence, surveys on freshwater fish composition along the altitudinal gradients of the Baleh River Basin in Sarawak, Borneo were conducted from April 2014 to August 2015. The Baleh River Basin was divided into seven altitudinal groups with a total of 72 stations. Group elevation ranged from 53 to 269 m above sea level. The fish samples and environmental parameters were taken concurrently during samplings. A total of 3565 specimens belonging to six orders, 14 families, and 76 species were found in the present study. The most dominant family in the Baleh River Basin was Cyprinidae (74.4%), followed by Gastromyzontidae (16.2%) while the most dominant species was Tor tambra (12.9%), followed by Lobocheilos ovalis (12.3%). Fish abundance significantly higher at high altitude sites than those at low altitude sites except for Mengiong River which has the lowest fish abundance despite with high elevation. Species richness was found significantly lower in midstream segment. Noticeable altitudinal gradient of fish assemblages was observed along the Baleh River except a discontinuity at the midstream segment which is attributable to the poorer quality inflow from the Mengiong River coupled with the meandering feature of the segment. Fish abundance was significantly and positively correlated with elevation, water pH and conductivity while negatively correlated with turbidity. Anthropogenic activities in the Baleh River Basin had altered the environmental variables thus disrupted the altitudinal gradient of fish assemblages. This phenomenon is apparent when the Canonical Correspondence Analysis (CCA) revealed that the first axis (CCA1) explained 42.5% of the variation and has positive loading on dissolved oxygen (DO) and negative loading on water conductivity; whereas CCA2 explained 37.5% of the variation and positively loaded on elevation, water pH, and DO. The results demonstrated that Gastromyzon fasciatus preferred more oxygenated water than Protomyzon sp., G. sp 1, and G. punctulatus although they are all from Gastromyzontidae family that inhabiting high altitude sites. Barbonymus schwanenfeldii was also found most abundant with elevated dissolved oxygen value. On the other hand, Rasbora volzii and R. hosii inhabiting lower altitude sites with less oxygenated and more acidic water.

Assessing Spatial and Temporal Trends in a Mediterranean Fish Assemblage Structure

Coastal fishes are not only valuable elements of marine biodiversity, but they also play an important ecological role in the functioning of coastal ecosystems: food resource, transfer of nutrients, predators. Therefore, data on the compositions of fish assemblages are of great importance. The objectives of the present study were to (i) define the faunistic characteristics of a typical fish community on the Mediterranean coast; (ii) investigate spatiotemporal changes in fish assemblages. Based on a set of indices (Fast protocol) and a long-term data set (6 years, 612 visual counts, 154 h of diving), changes in coastal fish communities were analyzed. Our results indicated that there was a significant shift in fish community structure, with a general decline of the calculated indices. In our study, part of the observed variability in fish assemblage structure could be due to different factors as site location and sampled year. The changes in the fish assemblages associated with inter-annual fluctuations observed in this study also provide important insights into how fish communities may change under environmental and anthropogenic influences.

Changes in fish assemblages following the implementation of a complete fishing closure in the Chishui River

The Chishui River is the first to have a complete fishing-closure in the Yangtze River basin. To explore how fish assemblages changed following the implementation of the fishing closure, field surveys were conducted biannually in three reaches (upper, middle and lower) along its longitudinal gradient during 2007 to 2019. A total of 143 species from eight orders and 24 families was collected. Diversity index for all three reaches showed no significant changes through time. However, non-metric multidimensional scaling (NMDS) ordination analysis revealed significant temporal changes in the structure of fish assemblages for all reaches (P＜0.05 in all cases). Time-lag analysis further showed that the fish assemblages in the upstream had reverted to the early study periods (P＜0.05), with the relative abundance of some large-sized species (e.g., Onychostoma simum and Spinibarbus sinensis) returning to former levels immediately after fishing closure. Fish assemblages in the midstream and downstream reaches also showed trends to returning to the early study periods, but did not reach statistical significance (P > 0.05). These discrepancies might be attributed to varying human disturbances and the type of fish species composition along the longitudinal gradient.

Spatial and seasonal patterns of fish assemblages in mountain streams of the Ren River, southwest China.

The spatial–temporal patterns of fish assemblages in lotic systems can provide useful information in developing effective conservation measures. This study aimed to explore the spatial and seasonal changes in fish assemblages and their association with environmental factors in mountain streams of the Ren River, southwest China. Field investigations were conducted at 18 sites during the rainy and dry seasons in 2017. A total of 1,330 individuals, belonging to three orders, eight families, 19 genera, and 21 species, were collected. Analysis of similarities (ANOSIM) showed that the structure of fish assemblages varied significantly at the spatial scale, but not at the seasonal scale. In low‐order sites, fish assemblages were mainly dominated by cold‐water and rheophilic species (e.g., Rhynchocypris oxycephalus, Scaphesthes macrolepis, Metahomaloptera omeiensis, and Gnathopogon herzensteini), while those in high‐order sites were predominated by warm‐water and eurytopic or stagnophilic species (e.g., Squalidus argentatus, Hemiculter leucisculus, and Zacco platypus). Canonical correspondence analysis (CCA) showed that the fish assemblages were structured by a combination of large‐scale landscape factors (e.g., altitude and C‐link) and small‐scale habitat features (e.g., channel width, water temperature, and depth). Among these factors, landscape had the greatest influence on fish assemblages, while local habitat variables were less important or were only significant in certain seasons.

Short-term change in fish assemblages after the passage of a typhoon in a temperate, coastal bay

To study the effects of a typhoon on a temperate, coastal bay community, the species composition, catch amount, and diversity of epipelagic fish assemblages were investigated. Fish samples were taken from catches of a purse seine fishery in Tachibana Bay, Japan between May and July 2011, covering before and after the passage of a typhoon in the area. Although major changes in total catch amount were not observed before and after the passage of the typhoon, the abundance of the Japanese anchovy, Engraulis japonicus Temminck et Schlegel, 1846, markedly decreased and bycatch of species increased, accompanied by increasing levels of diversity of the fish assemblage. Multivariate analysis showed that community differences before and after the passage were quantitative rather than qualitative. Comparisons in total length frequencies between the two periods indicated that specimens of the species compared were bigger in size for Trachurus japonicus (Temminck et Schlegel, 1844) and smaller for E. japonicus in the “after” period. These results suggest that the passage of the typhoon triggered not only interspecific faunal change but also intraspecific recruitment shifts in and around the bay.

Numerical abundance and biomass reveal different temporal trends of functional diversity change in tropical fish assemblages.

Understanding how the biodiversity of freshwater fish assemblages changes over time is an important challenge. Until recently most emphasis has been on taxonomic diversity, but it is now clear that measures of functional diversity (FD) can shed new light on the mechanisms that underpin this temporal change. Fish biologists use different currencies, such as numerical abundance and biomass, to measure the abundance of fish species. Nonetheless, because they are not necessarily equivalent, these alternative currencies have the potential to reveal different insights into trends of FD in natural assemblages. In this study, the authors asked how conclusions about temporal trends in FD are influenced by the way in which the abundance of species has been quantified. To do this, the authors computed two informative metrics, for each currency, for 16 freshwater fish assemblages in Trinidad's Northern Range that had been surveyed repeatedly over 5 years. The authors found that numerical abundance and biomass uncover different directional trends in these assemblages for each facet of FD, and as such inform hypotheses about the ways in which these systems are being restructured. On the basis of these results, the authors concluded that a combined approach, in which both currencies are used, contributes to our understanding of the ecological processes that are involved in biodiversity change in freshwater fish assemblages.

Effect of coastal development on larval fish abundance in Klang Strait (Malaysia)

Changes in larval fish assemblages were studied before (1985–86) and after (2013–2014) rapid coastal development in the Klang Strait, Malaysia, based on a Before-After-Control-Impact (BACI) experimental design. Fish larvae were sampled by bongo-nets along an 18-km transect from the impact station at the Kapar power station (KPS) to four control stations in increasingly offshore waters. Families Gobiidae, Clupeidae, Sciaenidae and Engraulidae were most abundant at both sampling periods, demonstrating their adaptability and resilience to the natural and anthropogenic disturbances. Coastal development has reduced larval fish abundance at KPS, inevitably shifting higher larval abundance to the control stations. This shift is related to lower sea surface temperature and higher pH. Despite the coastal disturbances, there was an overall increase in total larval fish abundance attributed to the preflexion stage of the Gobiidae, Sciaenidae, Engraulidae, Cynoglossidae and Callionymidae, and the yolk-sac and preflexion larvae of unidentified taxa.

Changes in reef fish assemblages in a cross-shelf euphotic-mesophotic gradient in tropical SW Atlantic

Despite a vast number of studies about shallow reef fish assemblages, and an increasing amount of studies about mesophotic ones, there are very few cross-shelf assessments including both, shallow and mesophotic depths. Herein, we analyze changes in reef fish assemblages in a cross-shelf euphotic-mesophotic (19–72.6 m) gradient in tropical SW Atlantic. Data was obtained using a novel low-cost 360° stationary video system. Sixty-four species from thirty families were identified. Depth, distance offshore and proportion of consolidated substrate were the main predictors of fish assemblages’ structure. Four distinct fish assemblages were identified across the depth gradient (20–30, 30–40, 40–50 and 50–75 m), with marked shifts in composition, abundance, and trophic structure. Abundance of invertebrate feeders and large roving herbivores declined across the shelf and with increasing depth, while abundance of planktivores and piscivores increased, particularly below 50 m. These changes were likely caused by changes in food availability and habitat suitability. Our low-cost video system yielded high-resolution images that enabled us to accurately survey reef fish assemblages, being therefore a useful method for studies focusing on both, euphotic and mesophotic reef ecosystems. Our results contribute to a better understanding of how reef fish assemblages change with increasing depth in SW Atlantic reefs and corroborate the idea that the breakpoint between euphotic and mesophotic fish assemblages is context-dependent rather than previously defined as 30 m depth.

High and dry in days gone by: Life‐history theory predicts Appalachian mountain stream fish assemblage transformation during historical drought

AbstractUnderstanding the ecological dimensions of drought is critical for predicting how humans and nature will be affected by the expected increased prevalence of drought in the future. We tested life‐history‐based predictions for fish assemblage responses to drought using retrospective analysis of long‐term (1986–2003) fish surveys from two streams in the Appalachian Mountains of North America. We hypothesised that (1) fish assemblage composition would correlate with wet and dry hydrologic conditions as assemblages fluctuated within a loose equilibrium and (2) life‐history traits of fishes would correlate with dry versus wet periods such that opportunistic life‐history strategists would dominate during drought. Results showed fish assemblage changes in Little River and Cataloochee Creek correlated with drought severity measured one year prior to fish surveys. Fish assemblages at all three sampling sites in Little River and two sites in Cataloochee Creek fluctuated within a loose equilibrium, while the remaining two sites in Cataloochee Creek indicated directional change. Life‐history traits for fishes in Cataloochee Creek correlated with one‐year time lag fluctuations in drought caused by opportunistic species being dominant during drought and periodic/equilibrium species dominant during wet periods. Time series plots of fish abundances aggregated by life‐history strategy revealed dominance of opportunistic species emerged at the onset of a multi‐year drought spanning 1998–2004, particularly for the two sites undergoing directional change. Our work provides empirical evidence for theoretical linkages between life history and environmental fluctuations and can ultimately be used to predict stream fish community response to future drought regimes.

Long-Term Changes in Fish Assemblage Structure in the Korea Strait from 1986 to 2010 in Relation with Climate Change

Climate change is expected to impact on marine-capture fisheries around the world. The Korea Strait showes the highest fisheries production among the adjacent seas of Korea, but studies on changes in the fish community related with climate change are scarce. We evaluated the spatio-temporal changes in fish assemblages, and their relationships with oceanic conditions in the Korea Strait (KS, 126°–129°5′E, 33°5′–35°N) to provide a scientific basis for developing fisheries policies to adapt to climate change and global warming. We used the inflow indices of the Korea Strait Bottom Cold Water and the Tsushima Warm Current, water temperature and salinity, and commercial fisheries catch data from 1986 to 2010. To detect temporal shifts in the oceanic conditions, we applied a sequential t test of regime shift. To evaluate spatio-temporal changes of the fish assemblage structure by year, month, and fishing block, we graphically summarized the species compositions of the commercial fisheries catch data by correspondence analysis (CA). We conducted cross-correlation and canonical CA to evaluate the relationship between the oceanic conditions and fish assemblages. Sardine and filefish dominated in spring and were mainly distributed far away from the coast. Anchovy were mostly caught in summer near the southeast coast of Korea, and their annual catch steadily increased. Squid and hairtail dominated in autumn–winter, and were mainly distributed from the northern part off Jeju Island to the southeast water of Korea. Chub mackerel were relatively constant in annual and seasonal catch. CA detected a shift in the fish assemblage between 1990 and 1991, which we speculated was triggered by the 1988–1989 regime shift in the North Pacific. Surface temperatures at 0–20 m depths, especially with a time lag of 1 year, were significantly correlated with the 1990–1991 shift in fish assemblage structure. We concluded that (1) the KS is an intermediate area between the waters of Ieodo and the East Sea with respect to the timing of shift in fish assemblage structure, (2) the regional shifts were characterized by the replacement of dominant fish species from sardine and filefish to chub mackerel and squid. We hope that further multidisciplinary studies between regional oceanographers and fisheries scientists will contribute to the development of fisheries policies through better understanding of the interactions between oceanographic processes and fishes at the regional scale in adaptation to climate change.