Academic literature on the topic 'Fish populations – New South Wales'

The common or weedy seadragon, Phyllopteryx taeniolatus, is an iconic and endemic fish found across temperate reefs of southern Australia. Despite its charismatic nature, few studies have been published, and the extent of population sub-structuring remains poorly resolved. Here we used 7462 single nucleotide polymorphisms (SNPs) to identify the extent of population structure in the weedy seadragon along the temperate southeast coast of Australia. We identified four populations, with strong genetic structure (FST = 0.562) between them. Both Discriminant Analysis of Principle Components (DAPC) and Bayesian clustering analyses support four distinct genetic clusters (north to south: central New South Wales, southern NSW, Victoria and Tasmania). In addition to these genetic differences, geographical variation in external morphology was recorded, with individuals from New South Wales shaped differently for a few measurements to those from the Mornington Peninsula (Victoria). We posit that these genetic and morphological differences suggest that the Victorian population of P. taeniolatus was historically isolated by the Bassian Isthmus during the last glacial maximum and should now be considered at least a distinct population. We also recorded high levels of genetic structure among the other locations. Based on the genomic and to a degree morphological evidence presented in this study, we recommend that the Victorian population be managed separately from the eastern populations (New South Wales and Tasmania).

Data from the New South Wales Rivers Survey on the occurrence of platypuses have provided the most recent and comprehensive record of platypus distribution in the State. The species was most commonly reported from the montane and coastal regions, being less common on the western slopes and uncommon in the rivers of the western lowlands. The observations confirmed those from earlier community-based surveys. In contrast to the distribution of native fish species, there appears to have been little change in the overall state-wide distribution of the platypus in response to degrading processes in the rivers of New South Wales, although nothing is known of the stability of their population numbers.

The parasite fauna of gemfish, Rexea solandri, from seven areas off southern Australia, was examined for evidence of isolated gemfish populations. Canonical multivariate analyses of data on larval nematodes (Anisakis spp. and Terranova sp.), cestode plerocercoids (Hepatoxylon trichiuri and Nybelinia sp.), acanthocephalans (Rhadinorhynchus sp. and Corynosoma sp.), and a hemiuroid digenean from a total of 763 gemfish showed that the parasite faunas of fish from eastern Australia were similar except for a sample taken off New South Wales at the end of the spawning season whose affinities are unknown. Fish from South Australia had similar parasite faunas to those collected from eastern Australia, suggesting that fish from the eastern and western Bass Strait belong to the same stock. Fish collected from the Great Australian Bight were distinct from the southern and eastern fish. Differences in parasite fauna were detected between samples taken within the spawning season and those taken from the same locations outside the spawning season, presumably a result of the spawning migration.

The geologically complex eastern Australian coastal margin supports the highest taxonomic diversity of freshwater fishes on the continent. However, mechanisms leading to coastal biogeographic patterns are poorly understood. A 399-bp fragment of the hypervariable mtDNA control region was sequenced from populations of eel-tailed catfish (Tandanus tandanus) to determine their phylogeographic structure and to relate this to proposed biogeographic mechanisms and landform evolution. Genetic structure in Tandanus is complex, with haplotypes clustering into three lineages: a phylogenetically distant, northern Queensland clade that is probably a new species; a mid-northern New South Wales clade corresponding to the recently discovered ‘Bellinger’ Tandanus cryptic species; and a third ‘derived’ clade T. tandanus. Phylogenetic analyses suggest that eastern Australian Tandanus originally invaded freshwaters from the coast where volcanic activity in the north and increasing aridity from the Paleocene reduced inter-fluvial connections, causing genetic divergence of northern Queensland and mid-northern New South Wales populations. The haplotypes represented by Murray–Darling drainage T. tandanus were the most derived, indicating that this species originally evolved on the coast and subsequently colonised the Murray–Darling basin. Tandanus in eastern Australia is phylogenetically structured and possibly comprises three species in this region; a pattern potentially shared by other eastern Australian freshwater fishes.

The maintenance of genetic diversity and gene flow in threatened species is a vital consideration for recovery programs. The endangered Oxleyan pygmy perch Nannoperca oxleyana has a fragmented distribution within coastal freshwater drainages of southern Queensland and northern New South Wales, Australia. In the present study, mitochondrial DNA control region variation was used to assess genetic diversity and structure across the geographical range of this species. Haplotypic diversity was highest in a small NSW subcatchment south of Evans Head (h = 0.594) followed by Marcus Creek in Queensland (h = 0.475). Distinct genetic differentiation was evident among the Queensland localities and the NSW subcatchments, implying restricted gene flow between coastal river systems. One of the nine haplotypes detected was distributed over 83.4% of the species’ range, suggesting historical connectivity among the now fragmented populations. These patterns were concordant with eustatic changes associated with the last glacial maximum. High barrier sand dunes may also act as barriers to gene flow and dispersal between adjacent NSW subcatchments. Conservation efforts should focus on the preservation of genetic diversity by maintaining as many genetically differentiated populations as possible. The relatively diverse populations inhabiting the South Evans Head subcatchment and Marcus Creek require special management consideration.

The vulnerability of marine fish species, particularly those inhabiting coastal waters, is an increasingly important issue in marine conservation. Although the weedy seadragon Phyllopteryx taeniolatus (Lacepede, 1804), a syngnathid fish endemic to southern Australia, is legally protected in New South Wales, there are no studies on population density, habitat use and behaviour to support this protection. We investigated the abundance, sex ratios and distribution of the weedy seadragon at three sites near Sydney, Australia. The distribution, density and sex ratios of seadragons were temporally stable, suggesting no large-scale seasonal migrations. Estimated population densities varied among sites from 10 individuals per ha to 65 individuals per ha, with sex ratios close to 1 : 1. Survival rates from one encounter to the next (approximately weekly) were high, being slightly lower for males (0.985 ± 0.006, mean ± se) and females (0.987 ± 0.005) compared with juveniles (1.000 ± 0.000). All size classes and both sexes were most common near the border of kelp and sand except when exhibiting hiding behaviour, when they were more often found in kelp beds. Kelp beds were the least-used habitat when feeding. Pregnant males tended to hide more often than other groups and therefore were more frequently found in kelp and kelp patches. Seadragons tended to be solitary, although pairing and grouping behaviour was also observed. Results of the present study show that weedy seadragons are resident in the same area throughout the year and have a strong affinity with heavily weeded rock and/or sand habitat. It is therefore recommended that the current species-based protection laws be used in concert with habitat-protection zones as a necessary measure to ensure the conservation of weedy seadragon populations.

Caridina sp. is an atyid shrimp occupying coastal streams in south-eastern Queensland and northern New South Wales. Shrimps from two geographic regions in south-eastern Queensland were examined. An analysis of 7 allozyme loci showed very high levels of genetic differentiation among catchments (F ST = 0.65) with much lower levels within catchments. This indicates extremely limited dispersal among catchments with greater levels within catchments. The levels of genetic differentiation were even greater than previously reported for two other atyid shrimp species occurring in upland rainforest streams. Populations from the Noosa River were more similar to those from the Glasshouse Mountains than to those from the geographically closer Tin Can Bay streams. This pattern was remarkably similar to that of a fish species occurring in the same streams and may reflect a recent confluence of streams from the Glasshouse Mountains and the Noosa River regions.

The freshwater fish, Rhadinocentrus ornatus Regan, 1914, has a patchy distribution through coastal drainages of Queensland and New South Wales, eastern Australia. Isolated populations of R. ornatus are found on several islands, as well as in a disjunct northern population 350 km from its nearest conspecific population. Deoxyribonucleic acid was extracted and sequenced for the mitochondrial ATPase gene to describe the geographic and genetic subdivision within the species. Four major clades were identified. These clades diverged between two and seven million years ago and so represent long-term divisions and possible units of conservation. There are conservation implications in that the narrow and localised distribution of R. ornatus overlaps with an area of large-scale land clearing, high human population and threats from introduced exotic fish. A particularly high centre of Rhadinocentrus diversity in the Tin Can Bay area of Queensland presents some interesting questions about the evolution of the genus Rhadinocentrus.

Through the use of mitochondrial DNA (ATP8 gene), the prediction of intermediate genetic structuring was investigated in two species of estuarine glassfish (Ambassis marianus and Ambassis jacksoniensis) (Perciformes : Ambassidae) to determine the possibility of a generalised ‘estuarine’ genetic structure. Individuals were collected from estuaries in eastern Australia between Tin Can Bay (Queensland) in the north and Kempsey (New South Wales) in the south. Analysis of the haplotype frequencies found in this region suggested panmictic populations with star-like phylogenies with extremely high levels of genetic diversity, but with no correlation between geographic distance and genetic distance. Non-significant FST and ΦST suggested extensive dispersal among estuaries. However, Tajima’s D and Fu’s FS values suggest ‘mutation–genetic drift equilibrium’ has not been reached, and that population expansions occurring 262 000 (A. marianus) and 300 000 (A. jacksoniensis) years ago may obscure any phylogeographic structuring or isolation by distance. The finding of panmixia was contrary to the prediction of genetic structuring intermediate between that of marine fish (shallowly structured) and freshwater fish (highly structured), suggesting high dispersal capabilities in these species.

Many recent studies have sought to monitor health characteristics of seagrasses, including changes in aerial extent, biomass and fish community structure. While these studies have provided important information on the ecology of seagrass communities on southeast Australia, little attempt has been made to subject these sampling procedures to rigorous experimental testing and review. This study employed commonly-used standard methods for sampling seagrass community characteristics in two sites in New South Wales. Where possible, sampling protocols were tested for accuracy and efficiency at a range of temporal and spatial scales. The ARCView Geographic Information System was used to construct vegetation polygons of seagrass distribution on the Tweed River, and in the Ukerebagh Channel annually over a 5-year period. For one year (2000), distributions from identical photographs were mapped twice to identify procedural errors. In general, errors relating to incorrect boundary identification were low compared to inter-annual variability. Inter-annual variability in seagrass beds was higher than for adjacent mangrove and saltmarsh. Estimates of biomass were derived from standard replicate 0.25m x 0.25m quadrats. The experiment contrasted two sites of similar geomorphic setting. Ukerebagh Channel on the Tweed River, and Woolooware Bay with Botany Bay are both shallow, sandy marine deltaic settings supporting stands of Zostera capricorni. Significant differences were found in the degree of replication required to identify significant changes in seagrass biomass at the two sites. Ukerebagh Channel supported relatively dense stands of Z. capricorni with low intra-site variability. Here 8 replicates were sufficient to detect 10 percent change. Towra Point presented a contrast, in which 15 replicates were required to detect a similar level of change. Woolooware Bay at Towra Point has suffered from increased sedimentation relating to alterations in current velocities at Towra Point, and the result highlights the greater degree of replication required to determine significance changes in disturbed systems. The fish populations in the seagrass at Towra Point were sampled using buoyant pop nets. Fish communities differed significantly from those sampled in adjacent mangrove and saltmarsh. Differences in fish assemblages between spring high tides, neap high tides and low tides are attributed to movements of fish between seagrass and adjacent mangrove and saltmarsh. This mosaic of habitats is utilized by a number of species over a tidal cycle, with seagrass providing an important low-tide refuge for many species utilizing mangrove and saltmarsh at high tide. Limitations in the efficiency of buoyant pop nets were exposed in a novel experiment which demonstrated differences in escape rates between species. Flat-tailed mullet (Liza argenta) are likely to be under-represented in experiments using this technique. Recommendations are made regarding optimal sampling protocols for monitoring seagrass in the region. All techniques tested are suitable, though some require modification. Some texts have under-estimated the degree of replication required to appropriately monitor changes in seagrass biomass in disturbed systems, where density is lower and intra-site variability higher. The buoyant pop-nets may require modification in open-water seagrass situations where escape by Liza argenta and Acanthopagrus australis were at unacceptable levels.

This thesis examines the release and long-term (>2 years) survival and growth of hatchery-reared larval and juvenile blacklip abalone (Haliotis rubra Leach), on natural coastal reefs in New South Wales (NSW), Australia. Abalone are demersal, relatively sedentary, marine molluscs, that support important commercial, recreational and indigenous fisheries in numerous locations around the world. This thesis was developed in response to substantial depletions of local populations of H. rubra along >250 km of the NSW coast and the ineffectiveness of traditional fisheries management strategies to arrest these declines. These failures stem from demographic processes, common to haliotids, that limit their ability to re-establish populations that have been subject to substantial decline. A series of laboratory and field experiments were designed and conducted to examine a range of factors, and their interactions, that can have substantial affects on the success of releasing hatchery-reared H. rubra to natural reefs. The principal finding was that successful stock enhancement of local populations can be achieved, and the greatest value of a stock enhancement strategy is likely to be gained where the primary management objective is rebuilding depleted natural populations. Methodology, baseline targets and other recommendations are provided that would aid implementation of a stock enhancement management strategy to complement current traditional fisheries management approaches. The objectives of the research in this thesis were to: 1) investigate factors affecting the settlement, metamorphosis and early growth of H. rubra larvae; 2) batch-tag larvae and juveniles to enable their identification when recaptured; 3) develop and test methods for the successful release of larvae and juveniles; 4) develop a monitoring strategy to estimate the abundance of released abalone through time; 5) quantify long-term survival and growth to provide minimum targets for stock enhancement; 6) determine the impact of releasing juveniles on wild populations; 7) provide a bio-economic analysis and; 8) provide recommendations for the implementation of a stock enhancement management strategy for H. rubra in NSW. The release of larvae to natural reefs requires them to be exposed to a number of handling and transport processes. In laboratory experiments conducted in this thesis, greater proportions (commonly >75%) of larvae settled, metamorphosed and grew to larger sizes when exposed to settlement substrata for longer periods of time (>24 hours). There was a lower settlement response in the presence of water flow, although the addition of gamma-aminobutyric acid (GABA) increased the proportion of larvae that settled within short periods of time, i.e. 25 - 100% more in ≤60 sec.. Larvae were resistant to simulated handling and transport processes, indicating their utility for stock enhancement. The tagging of larvae and juveniles is fundamental to assessing the success of an enhancement program. Hatchery-reared H. rubra larvae and juveniles were successfully batch-tagged. The tagging procedures provided an indelible mark, enabling the identification of individuals once recaptured, and unambiguous differentiation from wild conspecifics. Successful batch-tagging was also critical for the assessment of subsequent field experiments undertaken in this thesis. Larvae were batch-tagged with the epi-fluorescent dye, calcein. Laboratory experiments demonstrated that the tagged larval shell was clearly visible in the spire of juvenile shells after >250 days. The recapture of tagged and released larvae from natural reefs, >500 days after release, confirmed the persistence of this tag. A reliable and cost-effective method for batch-tagging juveniles was through the use of a commercial diet that resulted in the distinctive blue-green colouration of the shell. The presence of this blue-green colouration differentiated released juveniles from those in naturally occurring populations, could be observed with the naked eye, without the need for a UV light source, and persisted on the spire of individuals for >900 days. Methods of releasing H. rubra larvae and juveniles were developed and tested in a series of laboratory and field experiments. A deployment pump that included a pressurised container and hose, was used to successfully release larvae to natural reefs. The addition of GABA and refrigeration during simulated transport, and the stage of release from the deployment pump, significantly affected the number of larvae delivered through the pump. The release of larvae to physical shelters on the reef significantly increased the numbers that settled, and their survivorship. There was added complexity in the process of releasing juveniles than with that for larvae. The use of a deployment device (PVC tube, ~300 x 125 x 65 mm), that was securely placed onto the substratum, was integral to the successful release of juveniles. Use of these devices in a standard release protocol ensured the limited physical handling of juveniles and provided a simple, cost effective and efficient method for the release of large numbers to areas of natural reef. A monitoring strategy was developed and tested to enable accurate estimates of the abundance and therefore survival of released H. rubra ,of a variety of life history stages, to be measured. The abundance of H. rubra juveniles is difficult to accurately assess on natural reef because of their cryptic distribution among complex topography in rocky habitat. As a consequence, the precision and relative accuracy of methods to sample released abalone was examined in a series of field experiments, and included the dispersal of juveniles from deployment devices. The most accurate and precise estimates of the number of H. rubra surviving were detected using methods that disturbed the habitat, i.e. turning over boulders, within a release location, and multiple sampling approaches were required to measure the abundance of abalone of different sizes. For larvae, the collection of boulders provided more accurate estimates of abundance than samples taken using a venturi-lift. For juveniles, thorough searching of boulder substratum and more replicates provided more accurate estimates of abundance. Further, stratified sampling among habitats after natural disturbance revealed greater densities of H. rubra in 'solid habitat', and spatially stratified sampling indicated juveniles can disperse up to 10 m from their release point in <8 days. The success of a stock enhancement strategy is determined by the net value it adds to a population. This necessitates estimates of the long-term survival and growth of released individuals, the impact released individuals have on the extant population, and the bio-economic feasibility of an enhancement strategy. Rates of survival and growth varied substantially among releases and locations. However, the long-term survival of batch-tagged and released larvae and juveniles demonstrated that local populations of abalone could be enhanced with significantly greater numbers of juveniles surviving at multiple release locations than at control locations after >2 years. The release of juveniles had no detectable affect on the mean total number of wild conspecifics or wild recruits over these time scales. Long-term survival of released larvae and juveniles was generally low (<0.03%, range: 0 - 0.03% and; <4%, range: 0 - 10%, respectively). However, at three of the twelve juvenile release locations it exceeded that expected for wild abalone (range: 4 - 10%). Growth rates of released juveniles (range: 18 - 47 mm.yr-1) indicated that they would generally reach sexual maturity within 2 - 3 years and exceed the minimum legal length within 4.5 years. A deterministic, bio-economic model was used to analyse the net present value (NPV) of a stock enhancement strategy for H. rubra in NSW, against an alternate investment return of 10% p.a.. Positive NPV occurred where long-term survival was >4% and where growth rates were higher than average rates reported in this research, or beach price exceeded $AUD 34.kg-1. Low rates of long-term survival of larvae suggests their large-scale release is unlikely to provide a viable stand alone option to successfully enhance local populations of H. rubra. The survival and growth of released juveniles, to replicate locations, demonstrated that depleted local populations of H. rubra in NSW can be enhanced, and that a stock enhancement program can complement the NSW Abalone Fishery management strategy. The success of any large-scale stock enhancement program will be determined by the definition of its objectives. Outcomes from this thesis suggest that the greatest value of a stock enhancement strategy will be gained where its primary objective is to rebuild depleted populations, rather than optimise commercial yield through the release of individuals to overcome recruitment limitation or to harvest released individuals at a larger size. The decision to implement such a program, including explicit description of its primary objective, is required to be made among well-informed representatives of all stakeholders. Further, this decision needs to be made with a thorough understanding of the current biological structure of the populations, including the nature of population depletions, the economic status of the fishery and in light of current, complementary and alternative management arrangements that may provide comparative increases in net value.

Research Doctorate - Doctor of Philosophy (PhD)
Intermittently Closed and Open Lakes and Lagoons (ICOLLs) are coastal waterbodies that have intermittent connection to the ocean due to the formation of a barrier across the entrance. Catchment development is a major cause of pollution and also a justification for artificial barrier openings, which can have an adverse effect on the flora and fauna of ICOLLs. In most cases barrier openings may not have a direct effect on the biota of ICOLLs, but they can affect the factors which may influence invertebrate faunal and fish assemblages. The overall aim of this study was to determine what factors may influence fish assemblages of Central Coast ICOLLs. In order to understand these factors the research looked at the general ecology of Central Coast ICOLLs, including their invertebrate faunal assemblages and environmental parameters that may influence them (Chapter 3). Vegetated habitats within Central Coast ICOLLs include Ruppia sp. and the algae Chara sp. and Entermorpha intestinalis that support an invertebrate fauna dominated by polychaetes, crustaceans and molluscs. No single environmental variable had a major influence in structuring the invertebrate faunal assemblages at all four Central Coast ICOLLs. However, salinity was a major influencing factor at Cockrone, Avoca and Terrigal Lagoons, with percentage sediment composition a major factor at Wamberal Lagoon. Recruitment processes of larval and juvenile fishes are also presumably influenced by the status of the barrier. Larval and juvenile fishes occurring in Central Coast ICOLLs and their adjacent surf zones were identified to determine if movement of various species occurs once the barrier has been opened (Chapter 4). In this study, larval and juvenile fishes were more abundant in Central Coast ICOLLs but had lower species richness compared to their adjacent surf zones. The dominant larval and juvenile fish species found in ICOLLs included Ambassis jacksoniensis (Terrigal Lagoon), Philypnodon grandiceps (Avoca and Wamberal Lagoons) Atherinosoma microstoma (Wamberal Lagoon) and Acanthopagrus australis (Cockrone Lagoon). Hyperlophus vittatus was the dominant species collected from the adjacent surf zones. In this study there were no significant changes in larval and juvenile fish assemblages in either habitat from before to after barrier openings. Although some marine spawning species such as A. australis were present it could not be determined if these species were recruited from adjacent surf zones or from within these ICOLLs themselves. In most cases, Central Coast ICOLLs are considered to be generally self-recuiting environments, not for all species, but for many of their resident species of fish. Chapter Five determined the effects environmental parameters have on influencing fish assemblages. Fish assemblages of Central Coast ICOLLs showed low species richness, but high abundances of particular species when sampled using seine nets and multi-panel gillnets.Acanthopagrus australis (Cockrone Lagoon), Atherinosoma microstoma (Avoca and Wamberal Lagoons) and Ambassis jacksoniensis (Terrigal Lagoon) were the numerically dominant fish species collected using seine nets. Mugil cephalus was the species which was overall most frequently collected by gill netting. Fish assemblages were shown to be significantly different between Central Coast ICOLLs, and in this case were not directly influenced by barrier openings except at Wamberal Lagoon. However, Terrigal Lagoon, which had more barrier openings over the study period, compared to the other three ICOLLs, did have a higher diversity of fishes, which indicates that frequent barrier openings can influence fish assemblages. The major environmental influence on fish assemblages collected by seine nets at Cockrone and Wamberal Lagoons was salinity, and water temperature at Avoca and Terrigal Lagoons. The major environmental influence on fish assemblages collected by multi-panel gill nets at Cockrone and Avoca Lagoons was salinity, and water temperature at Terrigal Lagoon and >212 μm percentage sediment grain size at Wamberal Lagoon. Also, stochastic factors in the times and durations of barrier openings may play a large part in determining the fish assemblages that may be present at any one time in individual ICOLLs. High abundances of fish and their isolation from the ocean for long periods can result in competition for limited food resources, along with the effects that barrier openings may have on these resources not being fully understood (Chapter 6). Gut contents for each dominant species examined were similar; however each fish species had a dietary preference for a particular taxonomic group. Amphipods were the main dietary component of Acanthopagrus australis and Atherinosoma microstoma, with zooplankton being the main dietary component of Ambassis jacksoniensis. Barrier openings had a significant effect on the diets of A. australis (in Cockrone Lagoon) and A. microstoma (in Wamberal Lagoon), but not for species examined from Avoca and Terrigal Lagoons. Trace metal concentrations in sediments of Central Coast and Near-South Coast ICOLLs and gonad and liver tissues of Mugil cephalus were determined (Chapter 7). In the six ICOLLs studied, trace metal concentrations in both sediments and fish tissues were found to be relatively low and below guideline levels. Concentration levels did not differ significantly when compared between near-pristine (Termeil and Meroo Lakes), modified (Avoca and Terrigal Lagoons) and extensively-modified (Cockrone and Wamberal Lagoons) ICOLLs. Trace metal concentrations in sediments were not influenced by barrier openings. This study has shown that ICOLLs which are located geographically close to each other generally do not have similar environmental characteristics or fish assemblages which can be attributed to varying levels of development and land use activities within their individual catchments.

Murray cod Maccullochella peelii peelii is an iconic freshwater angling species that has suffered declines in abundance and is now listed as a nationally vulnerable species. Despite recognition of the need for biological knowledge to provide future management directions, little is known of its ecology. This thesis examines that ecology to provide new knowledge and recommendations for improved conservation management. (For complete abstract open document)

This chapter details the author's experience walking along the mud and rock edges of the Ashokan Reservoir to look for a Snow Bunting. Since the water from the Ashokan Reservoir glides south for over one hundred miles to supply New York City, the reservoir and the land around it are protected. The Department of Environmental Protection permits people to fish, but did not allow exploring the flats for birds. The author then went to East Kingston instead, where she finally saw some buntings. In the past forty years, Snow Bunting populations have dropped by 50 percent. Researchers do not know why, and their work is complicated by the fact that the bird breeds in such remote places. The Snow Bunting breeds in the Arctic then travels south for the winter looking for similar flat, wide-open landscapes.

<em>Abstract.</em>—Recent decades have seen substantial changes in fish assemblages in rivers of peninsular Florida. The most striking change has involved the addition of nonnative fishes, including taxa from Asia, Africa, and Central and South America. I review recent and historical records of fishes occurring in the Kissimmee River basin (7,800 km²), a low-gradient drainage with 47 extant native fishes (one possibly the result of an early transplant), at least 7 foreign fishes (most of which are widely established), and a stocked hybrid. Kissimmee assemblages include fewer marine fishes than the nearby Peace and Caloosahatchee rivers, and fewer introduced foreign fishes than south Florida canals. Fish assemblages of the Kissimmee and other subtropical Florida rivers are dynamic, due to new introductions, range expansions of nonnative fishes already present, and periodic declines in nonnative fish populations during occasional harsh winters. The addition, dispersal, and abundance of nonnative fishes in the basin is linked to many factors, including habitat disturbance, a subtropical climate, and the fact that the basin is centrally located in a region where drainage boundaries are blurred and introductions of foreign fishes commonplace. The first appearance of foreign fishes in the basin coincided with the complete channelization of the Kissimmee River in the 1970s. Although not a causal factor, artificial waterways connecting the upper lakes and channelization of the Kissimmee River have facilitated dispersal. With one possible exception, there have been no basinwide losses of native fishes. When assessing change in peninsular Florida waters, extinction or extirpation of fishes appears to be a poor measure of impact. No endemic species are known from peninsular Florida (although some endemic subspecies have been noted). Most native freshwater fishes are themselves descended from recent invaders that reached the peninsula from the main continent. These invasions likely were associated with major fluctuations in sea level since the original mid-Oligocene emergence of the Florida Platform. As opportunistic invaders, most native freshwater fishes in peninsular Florida are resilient, widespread, and common. At this early stage, it is not possible to predict the long-term consequences caused by the introduction of foreign fishes. We know a few details about the unusual trophic roles and other aspects of the life histories of certain nonnatives. Still, the ecological outcome may take decades to unfold.

<em>Abstract.</em>—Recent decades have seen substantial changes in fish assemblages in rivers of peninsular Florida. The most striking change has involved the addition of nonnative fishes, including taxa from Asia, Africa, and Central and South America. I review recent and historical records of fishes occurring in the Kissimmee River basin (7,800 km²), a low-gradient drainage with 47 extant native fishes (one possibly the result of an early transplant), at least 7 foreign fishes (most of which are widely established), and a stocked hybrid. Kissimmee assemblages include fewer marine fishes than the nearby Peace and Caloosahatchee rivers, and fewer introduced foreign fishes than south Florida canals. Fish assemblages of the Kissimmee and other subtropical Florida rivers are dynamic, due to new introductions, range expansions of nonnative fishes already present, and periodic declines in nonnative fish populations during occasional harsh winters. The addition, dispersal, and abundance of nonnative fishes in the basin is linked to many factors, including habitat disturbance, a subtropical climate, and the fact that the basin is centrally located in a region where drainage boundaries are blurred and introductions of foreign fishes commonplace. The first appearance of foreign fishes in the basin coincided with the complete channelization of the Kissimmee River in the 1970s. Although not a causal factor, artificial waterways connecting the upper lakes and channelization of the Kissimmee River have facilitated dispersal. With one possible exception, there have been no basinwide losses of native fishes. When assessing change in peninsular Florida waters, extinction or extirpation of fishes appears to be a poor measure of impact. No endemic species are known from peninsular Florida (although some endemic subspecies have been noted). Most native freshwater fishes are themselves descended from recent invaders that reached the peninsula from the main continent. These invasions likely were associated with major fluctuations in sea level since the original mid-Oligocene emergence of the Florida Platform. As opportunistic invaders, most native freshwater fishes in peninsular Florida are resilient, widespread, and common. At this early stage, it is not possible to predict the long-term consequences caused by the introduction of foreign fishes. We know a few details about the unusual trophic roles and other aspects of the life histories of certain nonnatives. Still, the ecological outcome may take decades to unfold.

<em>Abstract</em>.—Bartram’s Bass (an as yet unnamed species similar to Redeye Bass <em>Micropterus coosae</em>) is endemic to the Savannah drainage of South Carolina and Georgia. Hybridization between this native species and introduced Alabama Bass <em>M. henshalli </em>is widespread in the upper portions of the drainage. Recent studies have documented a precipitous decline in genetically pure Bartram’s Bass in Savannah drainage reservoirs and a corresponding increase in fish of hybrid origin. We surveyed tributary populations associated with these reservoirs and with the Savannah River main stem in 2004 and 2010. Results indicate an increased occurrence of hybrids in Bartram’s Bass native stream habitats over time. We also document the new occurrence of a second nonnative species, Smallmouth Bass <em>M. dolomieu</em>. Both Smallmouth Bass and their hybrids with Bartram’s Bass were collected from shoals in the Savannah River near the lower extent of the Bartram’s Bass range. Bartram’s Bass is a species of highest conservation concern in South Carolina, due to its limited native range and threats associated with hybridization. Conservation actions directed at this species, and its native stream habitats, will need to consider the establishment of nonnative species in the drainage and their potential to impact tributary populations over time.

<i>Abstract</i> .—Because of partial recirculation and steep bottom slopes, the Gulf of Maine (GoM) contains steep environmental gradients in both space and time. I focus, in particular, on optical properties associated with both resources and risks. The GoM estuary-shelf systems differ from those whose fine sediments are trapped behind barrier bars; in the GoM, nepheloid layers prevail over a wide range of depths, and onshore-offshore turbidity gradients at a given water depth are also steep. Turbidity reduces predation risk. Three crustacean species that are major fish forages respond to the strong environmental gradients in resources and risks by migrating seasonally both horizontally and vertically. Northern shrimp (also known as pink shrimp) <i>Pandalus borealis</i> , sevenspine bay shrimp <i>Crangon septemspinosa</i> , and the most common mysid shrimp in the GoM, <i>Neomysis americana</i> , share both stalked eyes that appear capable of detecting polarized light and statocysts. This pair of features likely confers sun-compass navigational ability, facilitating use of multiple habitats. All three species converge on a shallow-water bloom at depths <100 m of the western GoM shelf in December–March, well before the basin-wide, climatological spring bloom in April. In addition to reaching abundant food resources, I propose that they are also using optical protection, quantified as the integral of the beam attenuation coefficient from the surface to the depth that they occupy during daylight. Spring immigration into, and fall emigration from, estuaries appear to be common in GoM sevenspine bay shrimp and <i>N. americana</i> , out of phase with their populations south of New England and with turbidity differences a likely cause. Migration studies that include measurements of turbidity are needed, however, to test the strength of the effect of optical protection on habitat use by all three species. Simultaneous sampling of estuaries and the adjacent shelf, together with trace-element tracer studies, would be very useful to resolve timing and extent of mass migrations, which likely are sensitive to turbidity change resulting from climate change. These migrations present special challenges to ecosystem-based management by using so many different habitats.