Assessment of larval fish assemblages and nursery habitat in the St. Clair River delta (original) (raw)
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Larval fish assemblages and water mass history in a major faunal transition zone
Continental Shelf Research, 1999
A region of distinct oceanographic features that result from the meeting of several water masses is marked by Cape Hatteras, North Carolina, between the Middle Atlantic Bight (MAB) and South Atlantic Bight (SAB). The features are dynamic, corresponding, in part, to the degree of water exchange between the MAB and SAB. The extent of larval "sh transport via these features could have implications to "sh population genetics, yearclass structure, zoogeography, and access to nursery habitat. As a step in the examination of larval exchange between the MAB and SAB, we studied the association of spring larval "sh assemblages with environmental variables descriptive of the water mass origins. The region was clearly an oceanographic and ichthyoplankton faunal transition zone. Larval distribution corresponded to patterns of adult distributions along the entire eastern seaboard. High taxa-environment correlations described a boundary assemblage strongly in#uenced by oceanographic conditions. Net assemblages from mixed waters were dominated by taxa with widespread adult distributions (e. g. Peprilus triacanthus, synodontidae, triglidae, clupiedae, others) rather than a mix of taxa from other groups. MAB water contained Limanda ferruginea and Benthosema glaciale in deep, cold water and Glyptocephalus cynoglossus, Hippoglossina oblonga, Scomber scombrus, Lophius americanus, and others in shallow, warmer, less saline water. High densities of numerous sub-tropical species, (e.g. Xyrichtys novacula, Bothus spp.) and low densities of many others were found in SAB waters but varied greatly in distribution with depth. Taxa varied in their "delity to environmental indicators, thereby allowing for insight into the nature of the apparent di!erential permeability of this boundary zone to various species and into the precision of future (T.M. Grothues) Present address: Marine Biology and Fisheries, Rosenteil School of Marine and Atmospheric Sciences, 4600 Rickenbacker Causeway, Miami, FL 33149-1098, USA.
Canadian Journal of Fisheries and Aquatic Sciences
Larval fishes are sensitive to abiotic conditions and provide a direct measure of spawning success. The St. Clair – Detroit River System, a Laurentian Great Lakes connecting channel with a history of environmental degradation, has undergone improvements in habitat and water quality since the 1970s. We compared 2006–2015 ichthyoplankton community data with those collected prior to remediation efforts (1977–1978) to identify patterns in spatial and temporal variability. Both assemblages exhibited a predictable phenology, with taxa from the subfamily Coregoninae dominant in early spring followed by families Osmeridae, Percidae, and Moronidae (May–June) and Cyprinidae and Clupeidae (June–August). While higher densities of larval fish were found in the Detroit River, greater taxa richness and Shannon diversity were observed in the St. Clair River. System wide, 14 new taxa were observed in the 2000s study period. In addition, relative densities of two nonnative species, alewife (Alosa pse...
PLOS ONE
Climate change is leading to significant alterations to ecosystems all over the world and some of the resulting impacts on fish and fisheries are now becoming apparent. Estuaries, which are highly susceptible to climate change because they are relatively shallow and in close proximity to anthropogenic stressors, provide habitat to many fish species at a critical time in the life history, after transport and just prior to settlement in nurseries. Despite this, the long-term impacts of climate change on larval fish at this critical location/stage in the life history are not well documented. The larval fish assemblage of a coastal estuary was sampled once per week for twenty-six years at a fixed location in southern New Jersey, USA. We used ordination and regression analysis to evaluate the whole assemblage, individual species/family occurrence, and trends in total density and diversity over that time. The larval fish assemblage changed significantly in response to warming water temperatures. In addition, approximately one quarter of the species/families in the assemblage exhibited a statistically significant trend in individual occurrence over time. Of these, all five of the five northern-affiliated species decreased in occurrence while 18 of 21 southern-affiliated species increased in occurrence. Finally, total fish density and species diversity increased over the course of the study. The non-uniform response of the species/families in this larval assemblage is similar to what has been documented in other studies that evaluated the temporal trend of open ocean juvenile and adult fish assemblages.
Estuaries, 2005
We sampled nearshore fishes in the Saclamento-San Joaquin Delta, California, United States, during 2001 and 2003 with beach seines and gill nets. We addressed three questions. How and why did fish assemblages vary, and what local habitat features best explained the variation? Did spatial variation in assemblages reflect greater success of partioalar life history s~categies? Did fish biomass vary among years or across habitats? N o n m e h i c multidimensional scaling showed that habitat variables had more influence on fish assemblages than temporal variables. Results from both gear types indicated fish assemblages varied between Sacramento and San Joaquin River sampling sites. Results from gill net sampling were less pronounced than those from beach seine sampling. The Sacramento and San Joaquin river sites differed most notably in terms of water clarity and abundance of submerged aquatic vegetation (SAV), suggesting a link between these habitat characteristics and fish relative abundance. Among-site differences in the relative abundance of periodic and equilibrium s~categist species suggested a gradient in the importance of abiotic versus biotic community s~ucturing mechanisms. Fish biomass varied among years, but was generally higher in SAV-dominated habitats than the turbid, open habitats in which we found highest abundances of slliped bass Morone saxatilis and s~oecial-status native fishes such as delta smelt Hypomesus trampadficus, Chinook salmon Oncorhyncus tschawytscha, and spliflail Pogonichthys macrolepidotus. The low abundance of spedal-s~ams fishes in the comparatively productive SAV-dominated habitats suggests these species would benefit more from large-scale restoration aoions that result in abiotic variability that mirrors natural river-esluary habitat than from aoions that emphasize local (site-s])ecific t productivity.
Bulletin of Marine …, 1993
Numerical classification is used to examine broad scale spatial patterns in the larval component of the ichthyoplankton off the west and east coasts of the United States, based on data collected during extensive surveys over several years. The multispecies spatial patterns that emerged imply the existence of persistent and geographically distinct larval fish assemblages off both coasts. Four assemblages were identified off the west coast. They include a coastal assemblage that was restricted to coastal and continental shelf waters mainly off Washington and Oregon; a slope/transitional assemblage that occurred largely along the shelf edge and slope; a Columbia River plume assemblage that was associated with the Columbia River plume during summer; and an oceanic assemblage that prevailed in deep water beyond the shelf edge and for which northern and southern components were apparent during winter and spring. The east coast assemblages include a Gulf of Maine and Georges Bank assemblage; an oceanic assemblage that was associated with the continental shelf edge and slope; and a Middle Atlantic Bight assemblage that occurred along the shelffrom Cape Cod, Massachusetts, to Cape Hatteras, North Carolina. Northern, southern, inshore, and offshore components of the Middle Atlantic Bight assemblage were apparent at certain times of the year. In general, the boundaries to the assemblages are fluid, and seasonal variation in occurrence and abundance of species within assemblages is strong. The distribution of the larval fish assemblages reflects spatial structure in the oceanographic environment and, in some instances, can be related to specific hydrographic features. Among the fish taxa in both regions, adaptation of the spawning patterns to the prevailing oceanographic conditions is apparent. Co-evolution among the fishes' spawning strategies within the complex and variable marine ecosystems may have given rise to the high degree of structure observed in the ichthyoplankton spatial patterns and to the larval fish assemblages themselves. It is not possible to conclude from this limited study that the multispecies larval fish assemblages are independent ecological entities that enhance survival ofthe constituent species. Further investigations of finer scale spatial patterns within the larval fish assemblages and among different ontogenetic categories, as well as consideration of the zooplankton, of which fish larvae form only a small part, are necessary to understand fully the multispecies spatial patterns that prevail. LITERATURE CITED Azarovitz, T. R. and M. D. Grosslein. 1987. Fishes and squids. Pages 316-346 in R. H. Backus and P. W. Bourne, eds. Georges Bank. MIT Press, Cambridge, Massachusetts.
Zooplankton Dynamics in the Cache Slough Complex of the Upper San Francisco Estuary
San Francisco Estuary and Watershed Science
We studied abundance and dynamics of zooplankton in the tidal freshwater Cache Slough Complex (CSC) in the northern Delta of the San Francisco Estuary during June, July, and October 2015. We asked whether the CSC was an area of high zooplankton production that could act as a source region for open waters of the estuary. Abundance of the copepod Pseudodiaptomus forbesi was similar to that in freshwater reaches of the central and eastern Delta and higher than that in the adjacent Sacramento River. Growth rate of P. forbesi was higher than previously measured in large estuarine channels because of higher temperature and phytoplankton biomass in the CSC. Samples of P. forbesi examined with molecular techniques contained an unexpectedly high proportion of DNA from cyanobacteria and little DNA from more nutritious phytoplankton. We also examined tidal exchanges of phytoplankton biomass and copepods between Liberty Island, a shallow tidal lake within the CSC, and the adjacent southern Cache Slough, which links the CSC to the Sacramento River. We calculated zero net flux of phytoplankton over 127 days between June and October. The tidal flux of copepods, calculated using tidal flow from an in situ flow station and half-hourly sampling over three 24.8-hr tidal cycles, varied a great deal because of temporal patchiness and day/night variation in abundance. Overall, the tidal flux was indistinguishable from zero, while the tidally averaged water flow (and therefore the net copepod flux) was always into the wetland. Our results show some promise for the CSC as a productive habitat for planktivorous fishes and as a laboratory for learning how to design future wetland restoration. However, we remain cautious about whether wetlands such as the CSC may export large quantities of food organisms that can support fishes in other regions of the estuary.
Spatial and seasonal patterns in the crustacean zooplankton community of the St. Marys River
Lancet, 2011
Zooplankton communities of the Great Lakes have received significant attention in light of recent food web changes. No recent attempts have been made, however, to characterize the zooplankton community of the St. Marys River, the sole connecting channel between Lake Superior and Lake Huron. The purpose of this study was to provide new reference information for St. Marys River zooplankton communities and discuss the patterns observed in relation to recent changes in the Great Lakes. To address these objectives, sampling occurred at Lake Superior State University's Aquatic Research Laboratory from 2003 to 2007, and at 9 coastal wetlands in 2005. Compared to historical studies of St. Marys River riverine zooplankton, relative densities of calanoid copepods and daphnids have decreased while cyclopoid copepods and bosminids have increased. Coastal wetland communities continue to be diverse and exhibit similar community structure to previous studies, although Leptodora kindti, historically an abundant nearshore taxa, is now absent. Mechanisms driving differences in present community structure as compared to that noted in past studies of the St. Marys River are unknown but may be explained by the presence of the predatory, invasive zooplankton, Bythotrephes longimanus, local environmental variables, or changes upstream in Lake Superior. Temperaturezooplankton abundance patterns and nearshore community structure of Lake Superior are reflected in the St. Marys zooplankton community; thus, local environmental factors including changes in planktivory and proximity to upstream feeder communities likely play an important role in structuring St. Marys River zooplankton communities seasonally and spatially.
Larval fish assemblage recovery: a reflection of environmental change in a large degraded river
Restoration Ecology, 2014
Estuaries are globally important to fisheries but face many anthropogenic stressors that reduce water quality and degrade benthic habitat. The Maumee River estuary has been degraded by industrial contaminants, high sediment and nutrient loads, channelization and elimination of surrounding wetlands, lessening its value as spawning habitat for fishes of Lake Erie. Regulation and better management practices (BMPs) in the watershed have improved the water quality in this estuary, which should result in a response of the biotic community. We compared recent (2010/2011) larval fish assemblage data to similar data from the 1970s (1976/1977) in order to identify changes due to improved water and habitat quality. Family-level diversity was greater in recent study years compared to the 1970s and family richness increased from 6 to 10. In addition, the abundance of lithophilic spawning fishes was significantly greater in the recent study years. Increased diversity and family richness were consistent with increased water quality in the Maumee River whereas the observed increase in abundance of lithophilic spawners was consistent with an increase in the amount or quality of benthic habitat used by species in these families for spawning. Better wastewater management and agricultural practices in coastal watersheds can benefit the early life stages of fishes, thus benefitting coastal fisheries. Furthermore, larval fish assemblages may be useful indicators of biological integrity because of their sensitivities to environmental change. Routine sampling of estuarine larval fish assemblages could provide practitioners with insight into ecosystem changes and measure the response of the biotic community to restoration.
River Research and Applications, 2003
Physical conditions are usually considered pre-eminent in controlling river plankton, but biotic interactions may be important in slackwater areas. To begin testing this general hypothesis, we conducted a 12-day, predator-prey experiment in 3500 litre mesh enclosures in a slackwater area of the St. Lawrence River using planktivorous, juvenile yellow perch (Perca flavescens) and Dreissena mussels. Results generally supported our hypotheses that: (1) perch would directly suppress large zooplankton via predation but benefit microzooplankton through indirect interactions; and (2) dreissenids would directly depress rotifer densities via predation and have indirect negative effects on macrozooplankton. Based on gut contents of experimental fish, cladocera were the principal prey of smaller yellow perch (c. 46-50 mm), followed by copepods, ostracods, and rotifers. Larger juvenile perch (c. 67-73 mm) fed almost exclusively on copepods and ostracods. Densities of calanoid copepodids, nauplii, and some cyclopoid copepods (Diacyclops thomasi) were significantly depressed by perch, and adult Eurytemora affinis (99% of adult calanoids) essentially disappeared from fish enclosures. Despite being a favourite prey item of small perch, densities of the small cladoceran Bosmina (Sinobosmina) spp. were significantly higher when fish were present (150% greater than control densities on Day 12). Densities of the very abundant rotifer Polyarthra were >300% greater in fish enclosures than controls by Day 12, and the rotifers Synchaeta and predaceous Ploesoma were significantly more abundant in the presence of perch. Increases in rotifers and cladocera suggest indirect, positive effects of fish related to significantly higher phytoplankton biomass or decreased densities of predaceous copepods. Densities of eight of ten zooplankton groups examined declined significantly when mussels were present, and calanoid copepodids also declined but not significantly. Chlorophyll-a concentrations were slightly lower in mussel enclosures. This evidence suggests biotic interactions play important roles among potamoplankton in slackwater habitats, but river-wide implications of these findings require further study.