Movement of small‐bodied fishes from Lake Michigan into Chicago Area Waterways: Insights from otolith chemistry

The Chicago Area Waterways System (CAWS), an artificial connection between Lake Michigan (LMI) and the Illinois River watershed, has served as a conduit for invasive species and is a potential pathway for viral hemorrhagic septicemia (VHS) to spread from the Great Lakes into the Illinois River drainage. Although some fishes are known to have moved from LMI into the Illinois River via the CAWS, the rate of fish passage from the lake into the CAWS is unclear. Stable carbon isotopic signatures (δ¹³C) in otoliths differ between lake‐ and CAWS‐resident fish and were used as a natural tag to identify individuals that may have moved into the CAWS from LMI. The objectives of this study were to (i) estimate relative frequency of individuals with otolith δ¹³C indicative of prior residency in LMI among small‐bodied (<150 mm total length) VHS‐susceptible fishes collected from several locations in the CAWS, and (ii) to assess differences in relative frequency of probable immigrants from LMI among CAWS locations that differ in distance from the lake. Thirty‐six percent of small‐bodied fishes collected from the CAWS were identified as potential immigrants based on otolith δ¹³C. The percentage of individuals that had otolith δ¹³C suggestive of prior residency in LMI was higher among fish collected from the Calumet River compared to the Chicago River and North Shore Channel and decreased with increasing distance from lock and dam structures at the three entrances to the CAWS from the lake. Movement of small‐bodied fishes from LMI into the CAWS appears to be common and may represent a pathway for VHS‐susceptible species to transport the virus into the CAWS and potentially beyond.     

Metabolic costs of capital energy storage in a small‐bodied ectotherm

Reproduction is energetically financed using strategies that fall along a continuum from animals that rely on stored energy acquired prior to reproduction (i.e., capital breeders) to those that rely on energy acquired during reproduction (i.e., income breeders). Energy storage incurs a metabolic cost. However, previous studies suggest that this cost may be minimal for small‐bodied ectotherms. Here I test this assumption. I use a laboratory feeding experiment with the European green crab Carcinus maenas to establish individuals with different amounts of energy storage. I then demonstrate that differences in energy storage account for 26% of the variation in basal metabolic costs. The magnitudes of these costs for any individual crab vary through time depending on the amount of energy it has stored, as well as on temperature‐dependent metabolism. I use previously established relationships between temperature‐ and mass‐dependent metabolic rates, combined with a feasible annual pattern of energy storage in the Gulf of Maine and annual sea surface temperature patterns in this region, to estimate potential annual metabolic costs expected for mature female green crabs. Results indicate that energy storage should incur an ~8% increase in metabolic costs for female crabs, relative to a hypothetical crab that did not store any energy. Translated into feeding, for a medium‐sized mature female (45 mm carapace width), this requires the consumption of an additional ~156 mussels annually to support the metabolic cost of energy storage. These results indicate, contrary to previous assumptions, that the cost of energy storage for small‐bodied ectotherms may represent a considerable portion of their basic operating energy budget. An inability to meet these additional costs of energy storage may help explain the recent decline of green crabs in the Gulf of Maine where reduced prey availability and increased consumer competition have combined to hamper green crab foraging success in recent years.     

Scale dependence of sex‐specific movement in a small‐bodied stream fish

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Body size estimation of small‐bodied humans: Applicability of current methods

Body size (stature and mass) estimates are integral to understanding the lifeways of past populations.Body size estimation of an archaeological skeletal sample can be problematic when the body size or proportions of the population are distinctive. One such population is that of the Holocene Later Stone Age (LSA) of southern Africa, in which small stature (mean femoral length = 407 mm, n = 52) and narrow pelves (mean bi‐iliac breadth = 210 mm, n = 50) produce a distinctive adult body size/shape, making it difficult to identify appropriate body size estimation methods. Material culture, morphology, and culture history link the Later Stone Age people with the descendant population collectively known as the Khoe‐San. Stature estimates based on skeletal “anatomical” linear measures (the Fully method) and on long bone length are compared, along with body mass estimates derived from “morphometric” (bi‐iliac breath/stature) and “biomechanical” (femoral head diameter) methods, in a LSA adult skeletal sample (n = 52) from the from coastal and near‐coastal regions of South Africa. Indices of sexual dimorphism (ISD) for each method are compared with data from living populations. Fully anatomical stature is most congruent with Olivier's femur + tibia method, although both produce low ISD. McHenry's femoral head body mass formula produces estimates most consistent with the bi‐iliac breadth/staturemethod for the females, although the males display higher degrees of disagreement among methods. These results highlight the need for formulae derived from reference samples from a wider range of body sizes to improve the reliability of existing methods. Am J Phys Anthropol, 2010. © 2009 Wiley‐Liss, Inc.     

Regional movement patterns of a small‐bodied shark revealed by stable‐isotope analysis

This study used stable‐isotope analysis to define the nearshore regional residency and movements of the small‐bodied Australian sharpnose shark Rhizoprionodon taylori. Plasma and muscle δ¹³C and δ¹⁵N of R. taylori were collected from across five embayments and compared with values of seagrass and plankton from each bay. Linear distances between adjacent bays ranged from 30 to 150 km. There was a positive geographic correlation between R. taylori tissue and environmental δ¹³C values. Populations with the highest tissue δ¹⁵N were collected from bays that had the highest environmental δ¹⁵N values. These results suggest that R. taylori did not forage more than 100 km away from their capture location within 6 months to 1 year. The successful application of isotope analysis to define R. taylori movement demonstrates that this technique may be used in addition to traditional methods to study the movement of sharks, even within similar habitats across regionally small spatial scales (<100 km).     

Validation of swabs as a non-destructive and relatively non-invasive DNA sampling method in fish

Non-destructive methods of collecting DNA from small fish species can be problematic, as fin clips can potentially affect behaviour or survivorship in the wild. Swabbing body mucus may provide a less invasive method of DNA collection. However, risk of contamination from other individuals in high density groups could give erroneous genotyping results. We compared multilocus microsatellite genotypes from the same individuals when collected at low and high density and compared this with fin clips. We found no differences between these categories, with a genotyping error rate of 0.42%, validating the use of body mucus swabbing for DNA collection in fish.     

The perils of plasticity: dual resource pulses increase facilitation but destabilize populations of small‐bodied cavity‐nesters

Resource pulses within structured communities can lead to changes in the ecological roles of community members, particularly for species that exhibit plasticity in resource use. The red‐breasted nuthatch Sitta canadensis is a facultative excavating cavity‐nester that forages on seeds and insects, thus exhibits plasticity in both nesting habits and diet. In a long‐term study of cavity‐nesting vertebrates, we used point counts, and nest and vegetation surveys to examine the effects of two resource pulses of mountain pine bark beetle prey Dendroctonus ponderosae and tree cavities via excavator populations, on population densities and cavity reuse of red‐breasted nuthatches, from 1997–2006. We observed a doubling in mean nut‐hatch densities from 0.12 to 0.24 individuals ha^?1 then a collapse later in the decade to 50% below endemic levels (0.06 individuals ha^?1). These regional fluctuations were positively correlated with densities of trees recently infected by bark beetles. Because nuthatches range over large areas in winter, this regional correlation suggests that populations responded to the increase in winter food supply. At the site scale, general linear mixed effects models showed that nuthatch populations increased following years of high densities of downy woodpeckers Picoides pubescens, suggesting that downy woodpeckers were important facilitators, via cavity excavation. Type of nesting cavity used by nuthatches varied during the pulse, such that the use of existing cavities (in lieu of excavation) increased on sites that had harboured downy woodpecker nests in the previous year. We conclude that increased densities of cavity excavators allowed facultative excavators to increase their reuse of cavities, which may have contributed to the dramatic increases in nuthatch populations. However, nuthatch populations collapsed after the boom suggesting that this dual resource pulse may have destabilized populations by enabling densities to reach unsustainable levels. Thus, plasticity in resource use can have serious costs as well as benefits.     

Comparative use of side and main channels by small‐bodied fish in a large,unimpounded river

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Habitat preferences and habitat restoration options for small‐bodied and juvenile fish species in the northern Murray–Darling Basin

Degradation of instream habitats in the northern Murray–Darling Basin has occurred through numerous stressors, including siltation, clearing of bankside vegetation, intrusion of livestock and impacts of pest species. A better understanding of habitat preferences of native fish species could help guide future instream habitat restoration actions. The habitat choices of seven native fish species, juvenile Murray Cod (Maccullochella peelii), juvenile Golden Perch (Macquaria ambigua ambigua), juvenile Silver Perch (Bidyanus bidyanus), adult Murray–Darling Rainbowfish (Melanotaenia fluviatilis), adult Olive Perchlet (Ambassis agassizii), adult Un‐specked Hardyhead (Craterocephalus stercusmuscarum fulvus) and adult carp gudgeons (Hypseleotris spp.) were tested in preference troughs to help inform potential habitat restoration actions in the Condamine catchment. Each species was given a choice between pair combinations of open sandy habitat, submerged macrophytes, emergent plants and rocky rubble. Habitat preferences varied between species. Murray Cod, Golden Perch, carp gudgeons and Olive Perchlets preferred structure over open sandy habitat, whilst juvenile Silver Perch, Un‐specked Hardyhead and Murray–Darling Rainbowfish did not avoid open sandy habitats. Juvenile Murray Cod preferred rocky rubble habitat over all other habitat choices. Use of complex rock piles to provide nursery habitat for Murray Cod populations is a potential restoration option. Introduction of rock could also benefit Golden Perch and carp gudgeons. Use of emergent plants, submerged macrophytes and rocky rubble for habitat restoration all appear to have merit for one or more species of small‐bodied fishes or juvenile stages of larger sized fishes. Rocky rubble or floating attached macrophytes could be viable restoration options in areas too turbid to establish submerged macrophytes. These habitat interventions would complement existing actions such as re‐snagging and provision of fish passage to assist with sustainable management of native fish populations.     

Cloacal and buccal swabs are a reliable source of DNA for microsatellite genotyping of reptiles

In this study, a minimally invasive method for DNA sampling of reptiles and amphibians using cloacal and buccal swabs is described. High molecular weight DNA was isolated from the swabs, which were collected from tuatara (Sphenodon punctatus), and stored in 70% ethanol at room temperature for approximately 1 week. Amplification of mitochondrial and microsatellite DNA loci was successful from both cloacal and buccal swabs, and in all cases the genotypes matched those obtained from blood samples. These results show that cloacal and/or buccal swabbing is a useful alternative to blood sampling and toe clipping for genetic studies on reptiles. This method is rapid, inexpensive and easy to implement in field situations.     

Length–weight relationships for juvenile and small‐sized adult fishes of the surf zone

The present work provides length–weight relationships for 16 species captured in the surf zone of six sandy beaches near the mouth of the estuarine system of the Piraquê‐açú and Piraquê‐mirim rivers, southeastern Brazil.     

Ecological correlates of mammal β‐diversity in Amazonian land‐bridge islands: from small‐ to large‐bodied species

Aim

Mega hydroelectric dams have become one of the main drivers of biodiversity loss in the lowland tropics. In these reservoirs, vertebrate studies have focused on local (α) diversity measures, whereas between‐site (β) diversity remains poorly assessed despite its pivotal importance in understanding how species diversity is structured and maintained. Here, we unravel the patterns and ecological correlates of mammal β‐diversity, including both small (SM) and midsized to large mammal species (LM) across 23 islands and two continuous forest sites within a mega hydroelectric reservoir.

Location

Balbina Hydroelectric Dam, Central Brazilian Amazonia.

Methods

Small mammals were sampled using live and pitfall traps (48,350 trap‐nights), and larger mammals using camera traps (8,160 trap‐nights). β‐diversity was examined for each group using multiplicative diversity decomposition of Hill numbers, which considers the importance of rare, common and dominant species, and tested to what extent those were related to a set of environmental characteristics measured at different spatial scales.

Results

β‐diversity for both mammal groups was higher when considering species presence–absence. When considering species abundance, β‐diversity was significantly higher for SM than for LM assemblages. Habitat variables, such as differences in tree species richness and percentage of old‐growth trees, were strong correlates of β‐diversity for both SMs and LMs. Conversely, β‐diversity was weakly related to patch and landscape characteristics, except for LMs, for which β‐diversity was correlated with differences in island sizes.

Main conclusions

The lower β‐diversity of LMs between smaller islands suggests subtractive homogenization of this group. Although island size plays a major role in structuring mammal α‐diversity in several land‐bridge islands, local vegetation characteristics were additional key factors determining β‐diversity for both mammal groups. Maintaining the integrity of vegetation characteristics and preventing the formation of a large set of small islands within reservoirs should be considered in long‐term management plans in both existing and planned hydropower development in lowland tropical forests.

     

Investigating a simplified method for noninvasive genetic sampling in East African mammals using silica dried scat swabs

Swabbing scat has proved to be an effective noninvasive method to collect DNA from mammals in the field. Previously, this method has relied on preservative liquids or freezing to preserve the DNA collected on swabs. In this study, we determine the effectiveness of using silica to simply dry the swab in field as an alternative way to prevent DNA degredation. Four species were included in the study; reticulated giraffe, impala, fringe‐eared oryx, and lion. Swabs were taken at multiple time points for giraffe and impala scat samples, with the lion and oryx sampled opportunistically. Mitochondrial DNA was successfully amplified and sequenced from scat swabs from all species; however, effectiveness varied between species, with 81.8% amplification success rate from swabs taken from impala scat compared to 25% amplification success rate in giraffe. This variation in success rate was overcome by taking multiple swabs, thus increasing the probability of a successful amplification. The true merit of this method is in its simplicity and cheapness; no preservative liquids were required to be brought into the field, at no stage in the 2 weeks of field sampling were samples frozen, and no commercial kits were used for DNA extraction.     

Long‐term persistence of horse fecal DNA in the environment makes equids particularly good candidates for noninvasive sampling

Fecal DNA collected noninvasively can provide valuable information about genetic and ecological characteristics. This approach has rarely been used for equids, despite the need for conservation of endangered species and management of abundant feral populations. We examined factors affecting the efficacy of using equid fecal samples for conservation genetics. First, we evaluated two fecal collection methods (paper bag vs. ethanol). Then, we investigated how time since deposition and month of collection impacted microsatellite amplification success and genotyping errors. Between May and November 2014, we collected feral horse fecal samples of known age each month in a feral horse Herd Management Area in western Colorado and documented deterioration in the field with photographs. Samples collected and dried in paper bags had significantly higher amplification rates than those collected and stored in ethanol. There was little difference in the number of loci that amplified per sample between fresh fecal piles and those that had been exposed to the environment for up to 2 months (in samples collected in paper bags). After 2 months of exposure, amplification success declined. When comparing fresh (0–2 months) and old (3–6 months) fecal piles, samples from fresh piles had more matching genotypes across samples, better amplification success and less allelic dropout. Samples defecated during the summer and collected within 2 months of deposition had highest number of genotypes matching among samples, and lowest rates of amplification failure and allelic dropout. Due to the digestive system and amount of fecal material produced by equids, as well as their occurrence in arid ecosystems, we suggest that they are particularly good candidates for noninvasive sampling using fecal DNA.     

Single nucleotide polymorphism‐based dispersal estimates using noninvasive sampling

Quantifying dispersal within wild populations is an important but challenging task. Here we present a method to estimate contemporary, individual‐based dispersal distance from noninvasively collected samples using a specialized panel of 96 SNPs (single nucleotide polymorphisms). One main issue in conducting dispersal studies is the requirement for a high sampling resolution at a geographic scale appropriate for capturing the majority of dispersal events. In this study, fecal samples of brown bear (Ursus arctos) were collected by volunteer citizens, resulting in a high sampling resolution spanning over 45,000 km² in Gävleborg and Dalarna counties in Sweden. SNP genotypes were obtained for unique individuals sampled (n = 433) and subsequently used to reconstruct pedigrees. A Mantel test for isolation by distance suggests that the sampling scale was appropriate for females but not for males, which are known to disperse long distances. Euclidean distance was estimated between mother and offspring pairs identified through the reconstructed pedigrees. The mean dispersal distance was 12.9 km (SE 3.2) and 33.8 km (SE 6.8) for females and males, respectively. These results were significantly different (Wilcoxon's rank‐sum test: P‐value = 0.02) and are in agreement with the previously identified pattern of male‐biased dispersal. Our results illustrate the potential of using a combination of noninvasively collected samples at high resolution and specialized SNPs for pedigree‐based dispersal models.     

A non‐destructive sampling protocol for field studies of seed dispersal by fishes

This paper presents a standardized protocol for the non‐lethal capture of fishes, sampling of stomach contents and quantification of seed dispersal efficiency by frugivorous fishes. Neotropical pacu Piaractus mesopotamicus individuals were collected with fruit‐baited hooks. The diets of 110 fish were sampled using a lavage method, which retrieved >90% of stomach contents of both juveniles and adults and allowed individuals to recover within 5 min of treatment. The proportional volume of six food categories was similar for stomachs and whole digestive tracts retrieved by dissection. Fruit pulp was proportionally lower in the stomach. The abundance and species richness of intact seeds increased with fish size independent of whether only stomachs or whole digestive tracts were analysed. The analysis of stomach contents accounted for 62·5% of the total species richness of seeds dispersed by P. mesopotamicus and 96% of common seeds (seed species retrieved from more than one fish). Germination trials revealed that seed viability was similar for seeds collected from the stomach via lavage and seeds that passed through the entire digestive tract. Therefore, stomach contents provide an unbiased representation of the dietary patterns and seed dispersal of frugivorous fishes.     

Recruitment and growth of two small‐bodied resident fish species (Gobiidae and Atherinidae) in oligohaline,seasonally open lagoons

Spatio‐temporal recruitment patterns, growth and survival of the Swan River goby Pseudogobius olorum and western hardyhead Leptatherina wallacei are described from two small, coastal lagoons on the south coast of Western Australia. In these lagoons, estuarine salinity dynamics were relatively stable over much of the autumn–spring period when freshwater inputs from rivers were reduced and there was no oceanic connection. Preflexion and flexion stages of both fish species contributed strongly to population size structure in downstream reaches, whereas upstream reaches were dominated by postflexion larvae and juvenile stages. Spawning of both species was protracted and largely asynchronous, although the episodic presence of stronger preflexion and flexion cohorts suggested some synchronized spawning had occurred. Comparison with estuarine conditions over this period provided evidence that synchronized spawning may be related to temperature and salinity variations from a combination of freshwater inputs and periods of marine exchange. Uninterrupted growth and the progression of cohorts through to juvenile stages were consistent with the generally stable estuarine conditions. Larval and juvenile stages of both species were also tolerant of abrupt changes in salinity and temperature, which occurred due to a non‐seasonal oceanic connection. These findings were consistent with the euryhaline nature of adults of both species.