Early development of the northern logperch,Percina caprodes semifasciata,according to the theory of saltatory ontogeny

Synopsis The early development of northern logperch, Percina caprodes semifasciata, was examined from an ecological perspective and in relation to the theory of saltatory ontogeny. Steps, the intervals of relative homeostasis, separated by thresholds, rapid switches to new form and function resulting from canalization of changes in the preceeding step, are described and related to environmental factors. Adaptive shifts in growth allometries provided further evidence of the saltatory nature of ontogeny. Logperch eggs are small (1.2 mm diameter), demersal, and adhesive. The simple embryonic respiratory system reflects high oxygen availability on the lotic spawning grounds. Hatching occurs early, relative to other darters, and free embryos are pelagic. The small free embryos presumably drift downstream to lentic areas, where small planktonic food is more abundant. Logperch are therefore nonguarding, open substrate spawning lithopelagophils and, along with other Percina species, have not advanced from ancestral percid reproductive styles. Percina species have generally remained in ancestral habitats-rivers and lakes. The close correlation between developmental patterns of logperch and environmental factors is therefore interpreted as a restriction based on retention of ancestral characteristics, not as evidence of novel adaptations to new habitats.     

Isolation and identification of eight microsatellite loci in the Cherokee darter (Etheostoma scotti) and their variability in other members of the genera Etheostoma, Ammocrypta, and Percina

The Cherokee darter Etheostoma scotti is a federally threatened fish endemic to the Etowah River system of northwest Georgia. In order to analyse the population structure and genetic diversity of this fish, eight tetranucleotide microsatellite genetic markers were developed. The marker set was applied to 13 additional darter species to test cross-species amplification and polymorphism. Successful amplification was obtained for all eight loci in each of the 13 other species of darters, with between seven and eight polymorphic loci per species.     

Early development of the rainbow darter,Etheostoma caeruleum,according to the theory of saltatory ontogeny

Synopsis The early development of rainbow darter, Etheostoma caeruleum, was examined from an ecological perspective. Steps and thresholds of ontogeny to completion of body squammation are defined, and related to environmental factors. Rainbow darter eggs are about 2 mm diameter, considerably larger than those of related logperch (Percina caprodes). The embryonic vitelline respiratory plexus is much more extensive. The pelagic interval characteristic of logperch and ancestral percids is eliminated and onset of exogenous feeding is delayed. The larger larvae of the rainbow darter can begin feeding directly on aquatic insects, and complete their life cycle in streams. Therefore, shifts in the timing of important thresholds (e.g. exogenous feeding) are ecologically important. Furthermore, early maturation and/or delayed bone and scale formation may be responsible for reductions in the lateralis system and scalation in this and other darter species.     

Distribution and abundance patterns of rocky intertidal fishes in central California

Synopsis Distribution patterns and relative abundances were determined for rocky intertidal fishes in central California. Distributions were described relative to a categorization scheme of tidepools based on certain biotic and physical criteria. The fishes displayed a variety of distributions over tidepool categories and showed some segregation within categories.Cottids were the predominant tidepool fishes encountered, withOligocottus snyderi andClinocottus analis comprising 62% of all captures. The cebidichthyidCebidichthys violaceus and the stichaeidAnoplarchus purpurescens were also relatively common and dominated the out-of-water microhabitat.Oligocottus snyderi showed a minor shift in distribution over tidepool categories between seasons, and C. analis showed none, but both species varied substantially in abundance. Temporal changes in abundance of the more common species indicated seasonal trends, but the duration of the census period was insufficient to verify this.It is concluded that while species interactions may have influenced the observed patterns of habitat partitioning, the roles of predation and competition cannot be unambiguously defined. Presently, neither these nor historical factors can be discounted from having significantly influenced the evolution of the intertidal fish community.     

Diets of four sympatric species of Etheostoma (Pisces: Percidae) from southern Indiana: interspecific and intraspecific multiple comparisons

Synopsis The diets of four species of Etheostoma (E. spectabile, E. caeruleum, E. flabellare and E. nigrum) were investigated from ten Order 3 streams in the White River drainage of southern Indiana. All species fed mainly on insect larvae, primarily chironomids, ephemeropterans and plecopterans. Dietary proportions, as frequency of occurrence, were compared using cluster analysis based on matrices of values of Spearman rank correlation, Schoener index, Jaccard association, and Pearson's r. Certain species and, in some cases, stream pairs within species clustered closely in all analyses or in three of the four. Most clusters do not show closer intraspecific than interspecific similarity and specific streams had more influence than species in forming the logic of some clusters. It can be concluded that these fishes are opportunistic predators.     

Comparison of low oxygen avoidance in a bimodal breather,Erpetoichthys calabaricus and an obligate water breather,Percina caprodes

Synopsis Behavioral responses of the African reedfish, Erpetoichthys calabaricus, (Polypteridae), a bimodal breather, and the logperch, Percina caprodes, (Percidae), an obligate water breather, to low concentrations of dissolved oxygen were examined in a two-choice experimental design. In contrast to logperch, which consistently avoided dissolved oxygen concentrations of about 2.0 mg 1⁻¹, reedfish did not exhibit strong avoidance to dissolve oxygen concentrations of 0.5 mg 1⁻¹ and less.     

Habitat choice,recruitment and the response of coral reef fishes to coral degradation

The global degradation of coral reefs is having profound effects on the structure and species richness of associated reef fish assemblages. Historically, variation in the composition of fish communities has largely been attributed to factors affecting settlement of reef fish larvae. However, the mechanisms that determine how fish settlers respond to different stages of coral stress and the extent of coral loss on fish settlement are poorly understood. Here, we examined the effects of habitat degradation on fish settlement using a two-stage experimental approach. First, we employed laboratory choice experiments to test how settlers responded to early and terminal stages of coral degradation. We then quantified the settlement response of the whole reef fish assemblage in a field perturbation experiment. The laboratory choice experiments tested how juveniles from nine common Indo-Pacific fishes chose among live colonies, partially degraded colonies, and dead colonies with recent algal growth. Many species did not distinguish between live and partially degraded colonies, suggesting settlement patterns are resilient to the early stages of declining coral health. Several species preferred live or degraded corals, and none preferred to associate with dead, algal-covered colonies. In the field experiment, fish recruitment to coral colonies was monitored before and after the introduction of a coral predator (the crown-of-thorns starfish) and compared with undisturbed control colonies. Starfish reduced live coral cover by 95–100%, causing persistent negative effects on the recruitment of coral-associated fishes. Rapid reductions in new recruit abundance, greater numbers of unoccupied colonies and a shift in the recruit community structure from one dominated by coral-associated fishes before degradation to one predominantly composed of algal-associated fish species were observed. Our results suggest that while resistant to coral stress, coral death alters the process of replenishment of coral reef fish communities.     

Foraging modes of stream benthic fishes in relation to their predation effects on local prey density

Habitat use and foraging behavior of two benthic insectivorous gobies, Rhinogobius sp. CO (cobalt type) and Rhinogobius sp. DA (dark type), were examined in relation to their predation effects on local prey density in a small coastal stream in southwestern Shikoku, Japan. Correlations among the foraging range, frequency of foraging attempts and current velocity indicated that individuals using fast-current habitats had small foraging ranges and infrequently made foraging attempts while those in slow currents frequently foraged over large areas. The former and the latter were recognized as ambush and wandering foragers, respectively. Interspecific comparisons of habitat use, foraging behavior and prey preference suggested that Rhinogobius sp. CO selectively forage mobile prey by ambushing in fast currents, whereas Rhinogobius sp. DA randomly forage available prey by wandering in slow-current habitats. A cage experiment was conducted to assess prey immigration rate and the degree of predation effects on local prey density in relation to current velocity. The results of the experiment support, at least in part, our initial predictions: (1) prey immigration rates increase with current velocity and (2) the effects of fish predation on local prey density are reduced as current velocity increases. Overall results illustrated a link between the foraging modes of the stream gobies and their predation effects on local prey density: fish adopt ambush foraging in fast currents, where the decrease in prey density tends to be less, whereas fish actively forage over large areas in slow currents, where the decrease in prey is relatively large.     

Seasonal changes in low oxygen tolerance of fantail,Etheostoma flabellare,rainbow, E. caeruleum,and greenside,E. blennioides,darters

Synopsis The tolerance of fantail, rainbow, and greenside darters to low oxygen was determined by exposing fish to conditions of progressively decreasing oxygen levels and recording the oxygen concentration at which loss of equilibrium occurred. The greenside darter was least tolerant to low oxygen levels in summer, with loss of equilibrium occurring at a mean O₂ concentration of 3.39 mg l⁻¹. Tolerances then increased through spring. A similar trend was observed for the fantail darter, with the lowest tolerance occurring in summer (2.36 mg ⁻¹). and greatest tolerance in spring (2.03 mg l⁻¹). The rainbow darter exhibited its greatest tolerance to low oxygen in summer and spring (1.64 and 1.93 mg l⁻¹, respectively). Interspecific differences were greatest in summer, with greenside darters being the least tolerant to low oxygen levels and the rainbow darter being the most tolerant. No differences in tolerance among the species were noted in winter. The low oxygen tolerance exhibited in summer by the greenside darter may be due to a higher metabolic cost and a higher critical oxygen tension at maximal stream temperatures (>25° C). The observed differences in oxygen tolerance may influence the longitudinal distribution and habitat selection of darters, especially in the summer months.     

Patterns of food and microhabitat resource use by two benthic gobiid fishes

The mechanisms responsible for different patterns of habitat use by two benthic gobiid fishes, Acentrogobius sp. 1 and A. sp. 2, which displayed identical food use but resided in shallow and deep zones of coarse and fine sediments, respectively, in Lake Hamana, Shizuoka Prefecture, Japan, were investigated by field removal and laboratory sediment-grain size selection experimentation. Following field manipulation, involving removal of both species, the distribution patterns of each were found to be similar in both control and manipulated quadrats, suggesting their differential habitat use patterns may be the outcome not of competition but of differing preferences for habitat characteristics. Results of a sediment-grain size selection experiment in the laboratory suggested a weak preference of A. sp. 2 for fine sediment, while A. sp. 1 showed no grain size preference. The observed difference in the distribution patterns between these two species, therefore, may possibly have resulted from, at least in part, a combination of differences in their preference for sediment grain size and other habitat characteristics such as water depth.     

Reproductive biology and spawning habitat supplementation of the relict darter, Etheostoma chienense, a federally endangered species

We investigated the reproductive biology of Etheostoma chienense in the Bayou du Chien drainage of western Kentucky. Etheostoma chienense is similar in its ecology and reproductive biology to other members of the E. squamiceps complex. However, E. chienense is opportunistic in its choice of egg deposition substrates, as nests were found on a variety of natural and anthropogenic items. Due to an apparent lack of suitable spawning substrates, we added half-cylindrical ceramic tiles to several stretches of stream to increase potential nest productivity. Egg-clutches attached to artificial substrates were twice the size of egg clutches attached to naturally occurring materials. Laboratory experiments were conducted to determine nest rock size and mate choice preferences. Both the size of the male and of the nest rock appeared to be important parameters to spawning females. The life history information gathered here has significant management implications. Artificial spawning substrates should be placed in appropriate microhabitats (i.e., shallow, low-flow reaches in headwaters). Nest cavity vertical height should be about 3.0 cm and tiles should be spaced at least 0.5 m apart. We feel the use of surrogates (e.g., E. oophlyax) to investigate other types of spawning cover, and restoration of riparian buffer zones among other actions, would particularly benefit recovery efforts for this endangered species.     

Modelling the current distribution of European diadromous fishes: an approach integrating regional anthropogenic pressures

1. Twenty‐eight diadromous fish species occurred in Europe, North Africa and the Middle East in historical times. Their current distributions were assessed in terms of abundance classes (missing, rare, common and abundant) in 196 basins ranging from Morocco to northern Norway and from Greenland to Iran. 2. Their current distributions were modelled using abiotic, biotic, climatic and anthropogenic (regional anthropogenic pressures) variables. Anthropogenic variables were derived from characteristics of large dams (height, distance from the outlet, percentage of main stem river available downstream of dam) and human population density. These data were taken from the EEA Eldred 2.08 (European Lakes, Dams and Reservoirs Database) that deals comprehensively with large European dams and includes all obstacles of this type. To deal with ordinal response variables, we applied proportional odds models. 3. Twenty‐two species‐specific models were successfully built according to the reduction of deviance and the validation process, of which eight included one or more anthropogenic variables. No model could be established for six endemic or highly endangered species such as Acipenser sturio and Coregonus oxyrinchus. 4. Most response curves were easily interpretable since they were related to specific aspects of species’ ecology. Anthropogenic variables related to large dams impacted negatively on the distribution of diadromous fishes through the perturbation of river discharge patterns, the loss of river connectivity and the accessibility to essential habitats, particularly for Salmonid species that spawn in headwater streams. However, one species which can complete its life cycle using only the most downstream part of the basin, Liza ramada, was found to be favoured by the changes in hydrological regime. The bell‐shaped curves obtained from human population density for three diadromous species were connected on one side to a common settlement history of human and animal populations and on the other side to negative impacts of human activities arising at high population density. 5. Our approach can provide the basis for identifying special areas of conservation prior to planning restoration programmes at country or basin scales, as well as for more specialized studies focusing on one species only or at the local scale.     

Different roles of environmental variables and spatial factors in structuring stream benthic diatom and macroinvertebrate in Yangtze River Delta,China

Exploring the relative contribution of spatial factors and environmental variables in shaping communities is of widespread interest in biodiversity conservation and environmental management. Stream communities are hierarchically regulated by environmental variables over multiple spatial scales, and the reaction of different organisms to stressors are still equivocal. We sampled both macroinvertebrates and diatom at 80 sites and additional 10 sites for macroinvertebrates, field measured and laboratory analyzed environmental variables, from the tributaries of Qiantang River, Yangtze River Delta China in 2011. We used PCNM (principal coordinates of neighbor matrices) to generate spatial predictors. We applied redundancy analysis and variation partitioning procedures to identify key spatial and environmental factors, and to quantify their relative roles in shaping diatom and macroinvertebrate assemblages. Our results demonstrated the role of spatial and environmental variables differed in shaping benthic diatom and macroinvertebrate. Diatom assemblage variations were better explained by spatial factors, however macroinvertebrate assemblage variations were better explained by environmental variables. In terms of environmental variables, catchment scale variables (e.g., land use estimators, land use diversity) played the primary role in determining the patterns of both diatom and macroinvertebrate assemblages, whereas the influence of reach-scale variables (e.g., pH, substrates, and nutrients) appeared less. However, nutrients were the stronger factors influencing benthic diatom, whereas physical habitat (e.g., substrates) played more important role than water chemistry in structuring macroinvertebrates. Our results provided more evidence to the incorporation of spatial factors interpreting spatial patterns of stream organisms, and highlighted the useful of multiple organisms and environmental variables at different spatial scales in diagnosing mechanism of stream degradation and in building a sound stream conditions monitoring program for Yangtze River Delta.     

Habitat use and feeding behavior of thirteen species of benthic stream fishes

Synopsis The densities, habitat use, and feeding behaviors of 13 fish species belonging to the benthic invertebrate-feeding guild were studied by snorkeling at three localities in the Little River of eastern Tennessee, U.S.A. Resource partitioning occurred by habitat, feeding behavior and time of activity. Differences were also found at the generic level.Cottus was a nocturnal feeder, whereasPercina andEtheostoma were, for the most part, diurnally active.Percina moved about rapidly and spent most of its time above the bottom. In contrast,Etheostoma varied considerably in the amount of time spent under cover, spent little time above the bottom, and exhibited low levels of swimming activity. Nearly all species sought cover at night, suggesting they may be particularly sensitive to predation at night. Species with small adult sizes (Etheostoma, Cottus andP. evides) were concentrated in shallow water habitats, whereas species with large adult sizes (Percina) were more abundant in deep water habitats. The habitat use data are consistent with the hypothesis that size-selective predation by centrarchid bass may cause smaller fish to avoid deep water areas. Large species should have a lower risk of predation due to their size and behavior.     

Zoogeography and biodiversity of the freshwater fishes of Southeast Asia

The ichthyofauna of the freshwater system of Southeast Asia is extremely diverse. A recent estimate of about 1000 species is probably an understatement. More than 10 new species are being added to the list annually. The distribution pattern of the Southeast Asian freshwater fishes can be divided into five zoogeographic regions. The first one is the Salween basin in Burma, with fishes mainly of the Indian subcontinent origin such as Amblypharyngodon atkinsoni, Bangana almorae and Brachydanio jayarami. The second zoogeographic area is the Mekong, Chao Phraya and Mae Khlong drainages which harbour fishes typical of the mainland of Southeast Asia such as Acanthorhodeus deignani, Barbichthys nitidus and Cirrhinus siamensis. The Malay Peninsula is the third region whose species composition is heavily influenced by the Siamese (such as Homaloptera smithi, Tuberoschistura baenzigeri and Botia beauforti) and Indonesian (such as Botia hymenophysa, Luciocephalus pulcher and Parosphromenus deissneri) elements. The islands of Sumatra, Borneo and Java are the fourth zoogeographic area of fish distribution. These islands show a high degree of endemism, especially in fishes of the family Belontiidae. Finally, the freshwater system of the Philippines is the last zoogeographic region of Southeast Asia. The area is characterized by the presence of closely related species of the cyprinids especially in Lake Lanao. Currently, high diversity of these freshwater fishes is being threatened by land development, such as deforestation, road construction and land expansion for plantation. Recent studies in the Gombak River basin show the extermination of 41 per cent of native fish species from 1969 to 1990. This is probably due to the construction of highways, logging, as well as land clearing for agriculture.     

Diet overlap among two Asian carp and three native fishes in backwater lakes on the Illinois and Mississippi rivers

Bighead and silver carp are well established in the Mississippi River basin following their accidental introduction in the 1980s. Referred to collectively as Asian carp, these species are filter feeders consuming phytoplankton and zooplankton. We examined diet overlap and electivity of Asian carp and three native filter feeding fishes, bigmouth buffalo, gizzard shad, and paddlefish, in backwater lakes of the Illinois and Mississippi rivers. Rotifers, Keratella spp., Brachionus spp., and Trichocerca spp., were the most common prey items consumed by Asian carp and gizzard shad, whereas crustacean zooplankton were the preferred prey of paddlefish. Bigmouth buffalo diet was broad, including both rotifers and crustacean zooplankton. Dietary overlap with Asian carp was greatest for gizzard shad followed by bigmouth buffalo, but we found little diet overlap for paddlefish. Diet similarity based on taxonomy correlated strongly with diet similarity based on size suggesting filtration efficiency influenced the overlap patterns we observed. Although rotifers were the most common prey item consumed by both bighead and silver carp, we found a negative relation between silver carp CPUE and cladoceran density. The competitive effect of Asian carp on native fishes may be forestalled because of the high productivity of Illinois and Mississippi river habitats, yet the potential for negative consequences of Asian carp in less productive ecosystems, including Lake Michigan, should not be underestimated.     

Living benthic foraminifera of the Okhotsk Sea: Faunal composition, standing stocks and microhabitats

Live (Rose Bengal stained) benthic foraminifera were investigated in surface sediment samples from the Okhotsk Sea to reveal the relationship between faunal characteristics and environmental parameters. Live benthic foraminifera were quantified in the size fraction > 125 µm in the upper 8 cm of replicate sediment cores, recovered with a multicorer at five stations along the Sakhalin margin, and at three stations on the southwestern Kamchatka slope. The stations are from water depths between 625 to 1752 m, located close or within the present Okhotsk Sea oxygen minimum zone, with oxygen levels between 0.3 and 1.5 ml l^- 1. At the high-productivity and ice-free Kamchatka stations, live benthic foraminifera are characterized by maximal standing stocks (about 1700-3700 individuals per 50 cm²), strong dominance of calcareous species (up to 87-91% of total live faunas), and maximal habitat depths (down to 5.2-6.7 cm depth). Vertical distributions of total faunal abundances exhibit a clear subsurface maximum in sediments. At the Sakhalin stations, which are seasonally ice-covered and less productive, live benthic foraminifera show lower standing stocks (about 200-1100 individuals per 50 cm²), lower abundance of calcareous species (10-64% of total live faunas), and shallower habitat depths (down to 2.5-5.4 cm depth). Faunal vertical distributions are characterized by maximum in the uppermost surface sediments. It is suggested that 1) lower and strongly seasonal organic matter flux, caused by the seasonal sea ice cover and seasonal upwelling, 2) lower bottom water oxygenation (0.3-1.1 ml l^- 1), and 3) more pronounced influence of carbonate undersaturated bottom water along the Sakhalin margin are the main factors responsible for the observed faunal differences. According to species downcore distributions and average living depths, common calcareous species were identified as preferentially shallow, intermediate and deep infaunal. Foraminiferal microhabitat occupation correlates with the organic matter flux and the depth of the oxygenated layer in sediments.     

Group-living and the richness of the parasite fauna in Canadian freshwater fishes

Summary An increased transmission of ectoparasites among individual animals is considered to be an inevitable cost of living in groups, since several kinds of ectoparasites require close proximity between large numbers of hosts for successful transmission. However, we do not know whether individuals belonging to group-living species incur a greater risk of ectoparasitism than individuals of solitary species. Here, using published data from 3 families (60 species) of Canadian freshwater fishes, I test the hypothesis that group-living species are host to more species of contagious ectoparasites (copepods and monogeneans) than solitary host species. As the different fish species have been studied with varying intensity, I used the mean number of parasite species recorded per study as a standard measure of parasite numbers. Multiple regression analyses were performed separately for each family to determine the effects of group-living and of 3 other variables (host size, age, and range) on the richness of the recorded parasite fauna. Once the effects of the other variables were removed, I found no significant effect of sociality on the richness of the parasite fauna per fish species, for contagious ectoparasites and other types of parasites. Neither of the other variables had any influence on the numbers of parasite species per fish species. These results suggest that a richer ectoparasite fauna is not a cost of group-living in fishes.     

Intra- and interspecific cohabitation of scorpions in the field and the effect of density, food, and shelter on their interactions

Scorpion cohabitation was studied qualitatively and quantitatively for several years in the field and in controlled experimental conditions in the laboratory. In the field, several cases were recorded of scorpions sharing the same shelter, either intra- or interspecifically. Intraspecific cohabitation was more prevalent than interspecific cohabitation. Among the five scorpion species studied here, Compsobuthus werneri judaicus shows the highest degree of sociality and aggregates both intra- and interspecifically. Leiurus quinquestriatus was never observed to cohabit interspecifically. Both Buthotus judaicus and C. werneri judaicus shared shelters with other scorpions more frequently during the wet season, whereas Nebo hierichonticus and Scorpio maurus fuscus cohabitated more often during the dry season. Under controlled laboratory conditions, density and availability of either food or shelter appear to be significant in facilitating cohabitation, even in the more aggressive species. Received: April 28, 1999 / Accepted: July 30, 1999     

Under-ice observations of behavior of selected native and exotic fishes of the St. Lawrence river system

Winter behavior of two native fishes (yellow perch, Perca flavescens, and killifish, Fundulus heteroclitus) and an exotic (goldfish, Carassius auratus) were studied in an outdoor experimental pond to quantify and link behavior to environmental conditions, and to identify interactions among the species that now co-occur in the wild. Killifish had high mortality and were not observed. However, contrary to our predictions, perch and goldfish had good overwinter survival and remained active in winter, and neither species spent most of their time in the warmest layer of the water column. Only two instances of aggression were seen: in both, goldfish charged perch. Both species were found principally in groups (schools); goldfish spent 18% of their time in multispecies groups. © 1994 Wiley-Liss, Inc.