Seasonal spatial distribution of juvenile lake sturgeon in Muskegon Lake,Michigan, USA

We examined seasonal spatial distribution and diel movements of juvenile lake sturgeon Acipenser fulvescens in Muskegon Lake, Michigan (a protected, drowned river mouth lake that links the Muskegon River to Lake Michigan). We surgically implanted ultrasonic tags in 20 juveniles (age 1–7) captured in gill nets to track their locations during August–December 2008/2009 and September 2010–October 2011. Most juveniles were observed ≤1.5 km from the mouth of the Muskegon River in Muskegon Lake at a mean depth of 7.5 m (SE = 1.3 m) during summer. In fall, juveniles moved away from the river mouth to the deepest part of Muskegon Lake and were observed at a mean depth of 15.8 m (SE = 1.3 m) during winter. The shift in spatial distribution coincided with fall turnover (i.e., loss of thermal stratification) and with changes in dissolved oxygen (DO) concentrations in the hypolimnion. During summer, DO concentrations in the hypolimnion were typically <4 mg·l^?1 in the deepest part of Muskegon Lake and DO concentrations at locations of tagged lake sturgeon were >7 mg·l^?1 in 94% of instances. Tracking in 2009 revealed no significant change in depth distribution or movement over the diel cycle. We only observed two tagged juveniles immigrating to Lake Michigan, suggesting that juveniles use Muskegon Lake for multiple years. Our results suggest that: (i) Muskegon Lake serves as an important nursery habitat for juvenile lake sturgeon that hatched in the Muskegon River before they enter Lake Michigan and (ii) seasonal changes in DO concentration in the hypolimnion likely affect the spatial distribution of juveniles in Muskegon Lake.     

Möglichkeiten zum Nachweis von autochthonen Hochlagenbeständen der Fichte (Picea abies) in den Berchtesgadener Alpen

Zusammenfassung Bedingt durch Mangel an Wissen und zum Teil auch geeignetem Saat- und Pflanzgut wurden vor ca. 130 Jahren manche Best?nde in den Hochlagen der Berchtesgadener Alpen mit nicht angepa?ten Fichten-Herkünften (Picea abies) aus mittleren und tieferen Lagen begründet. Um den autochthonen Charakter und damit die Angepa?theit an die Umwelt von solchen Hochlagenbest?nden des Nationalparks einzusch?tzen, wurde mit Hilfe biochemisch-genetischer Methoden deren genetische Struktur an drei Enzym-Genloci bestimmt. An einem weiteren Enzym-Genlocus wurden Beziehungen zwischen dem jeweiligen Genotyp und dem Gesundheitszustand der B?ume überprüft Als Versuchsmaterial dienten Samenproben von 30 Einzelb?umen aus Best?nden unterschiedlicher H?henlage und eine Mischprobe von einem Tieflagenbestand nahe München. W?hrend die Daten von zwei Enzym-Genloci, an denen arealspezifische Allele vorkommen, zeigten, da? das untersuchte Fichtenmaterial nicht aus einem anderen Refugialgebiet stammt, ergaben die Genotyph?ufigkeitsverteilungen am dritten Genlocus (SAP-B), an dem bereits h?henlagen-abh?ngige Allelverteilungen nachgewiesen worden waren, da? Restbest?nde der h?chsten Gebirgslagen nur SAP-Hochlagentypen enthalten und damit, wie vermutet, als autochthon zu betrachten sind. Demgegenüber weisen die Best?nde der Tallagen überwiegend die SAP-Tieflagentypen, die Best?nde der mittleren Lagen jedoch alle SAP-Typen in unterschiedlicher H?ufigkeit auf, wobei in einem Fall die Vermutung der künstlichen Begründung gestützt werden konnte. Für einen weiteren Genlocus (GRD-A) wurde zudem beim Vergleich zwischen gesunden und immissionsgesch?digten B?umen festgestellt, da? bestimmte heterozygote Genotypen weitaus h?ufiger bei den gesunden Individuen vorkommen, was frühere Ergebnisse bei jüngeren Best?nden und Klonmaterial voll best?tigte. Generell zeigen die Ergebnisse dieser Untersuchung auf, wie die Autochthonie von Hochgebirgs-Fichtenbest?nden eingesch?tzt werden kann; ein Weg, der für waldbauliche und Generhaltungsma?nahmen von gro?er Bedeutung ist.

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Possibilities of detecting indigenous high-elevation Norway spruce (Picea abies) stands in the Berchtesgadener Alps

Summary The lack of sufficient seed and planting stock from high-elevation provenances of Norway spruce (Picea abies) led to the introduction of poorly adapted seed sources from low and middle elevations into the higher, elevations of the Berchtesgadener Alps. In order to evaluate the indigenous character and thus the adaptability of tree stands located at high elevations, their genetic structures using three enzyme gene loci were determined by means of biochemical-genetic methods. For another enzyme gene locus, the relationship between certain genotypes and the extent of pollution-caused damage of trees was examined. The test material consisted of seed lots from 30 single trees from stands at different elevations and from a bulk seed collection from a lowland stand near Munich. While the data of two enzyme gene loci possessing areal-specific alleles revealed that the investigated spruce stands do not originate from other distribution area,, the genotype frequencies of the third gene locus (SAP-B), for which elevational gradients in allele frequencies have already been established, were found to vary markedly among the spruce stands. Some tree groups from the highest altitudes in these Alps exhibited only those SAP genotypes which characterize high-elevation stands (high-elevation types) thus confirming their indigenous character. In contrast, the spruce stands from the valleys mainly consisted of low-elevation types and rarely of heterozygotes of both SAP types. The stands from middle- and higher-elevation sites, however, contained all three SAP types in different proportions, whereby in one case the assumption of an artificial regeneration with low elevation types was supported. For another enzyme gene locus (GRD-A), a comparison between healthy trees and such damaged by air pollution showed that certain heterozygotes occur more frequently among the healthy trees, which surprisingly well confirms the results from earlier studies on younger spruce stands and fumigated clone material. In general, the results of this study indicate possibilities of evaluating the indigenous character of high-elevation stands, which should be of value especially for silvicultural and gene conservation measures.

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Herrn Prof.H. Schmidt-Vogt zum 70. Geburtstag gewidmet.     

Spatiotemporal patterns of fish community composition in Great Lakes drowned river mouths

Freshwater river mouths in large lakes are centres of biological activity, yet little is understood about the spatial and temporal dynamics of fish communities in these systems. In the Laurentian Great Lakes, we sampled littoral fishes over 3 years in six drowned (i.e., protected) river mouths to: (i) quantify spatial (among river mouths) and temporal (among years) variation, (ii) evaluate associations with environmental conditions and (iii) assess spatial patterns of community similarity. We sampled 6787 fish representing 43 species over the course of the study. Multivariate analyses indicated that variation in fish species composition was more strongly partitioned among river mouths than among years. Fish communities across the six river mouths were partitioned into three groups, a pattern we attribute to variability in anthropogenic disturbance and environmental conditions. Canonical correspondence analysis showed that fish species composition was associated with specific conductivity, vegetation cover, turbidity and pH, suggesting species–environment relationships are similar to those shown for Great Lakes coastal wetlands. Finally, we found a negative relationship between geographic distance and community similarity, suggesting that dispersal and/or environmental gradients play a role in shaping these river mouth fish assemblages. We conclude that Great Lakes drowned river mouths can harbour diverse and spatially variable fish assemblages that are driven by a combination of local and regional factors.     

Genetic aspects of artificial regeneration of Douglas-fir (Pseudotsuga menziesii) in Bavaria

Douglas-fir has been planted in Bavaria for over 100 years. Its high growth potential and good wood quality combined with its silvicultural characteristics have increased interest in the species which can easily be integrated into existing natural ecosystems. In order to be successful in the establishment of Douglas-fir one must select the best provenance (only the so called “green” or viridis coastal type form is suitable for Bavaria), maintain a broad genetic base and carry out proper silviculture. The goal of the study was to check the origin/provenance (coastal or interior type) of older Bavarian Douglas-fir stands, the respective genetic variation of the stands and also the natural regeneration, the collected seed and the plants raised in the nursery. Possible changes in the genetic composition and diversity due to selective processes in the nursery phase were also investigated. Isoenzyme gene markers were used for the study. The majority of the investigated older stands apparently belong to the coastal type Douglas-fir; however, we also found mixed stands and stands solely of the interior (unsuitable) type. Older stands show large variation in their genetic diversity (v _gam between 19.9 and 90.1). Some of the stands of unsuitable provenance have natural regeneration and others have been selected as seed collecting stands. Through natural regeneration the genetic structure of the older stands is passed on to the following generation. The same is true for reproductive material collected from such stands. In comparison to seed collected from stands in the USA (from stands selected by the EU for seed collection), seed from Bavarian stands is genetically very heterogeneous in respect to the allele variants and the diversity. No significant changes in the genetic population structure were found in the nursery due to sowing or transplanting. The critical stage for obtaining high quality reproductive material of Douglas-fir is the selection of seed collecting stands and the harvesting procedure. The resulting consequences for seed collection and procurement of suitable reproductive material for Douglas-fir are discussed.     

Tracking SNARE complex formation in live endocrine cells

Syntaxin, synaptosome-associated protein of 25 kD (SNAP25), and vesicle-associated membrane protein/synaptobrevin are collectively called SNAP receptor (SNARE) proteins, and they catalyze neuronal exocytosis by forming a "core complex." The steps in core complex formation are unknown. Here, we monitored SNARE complex formation in vivo with the use of a fluorescent version of SNAP25. In PC12 cells, we found evidence for a syntaxin-SNAP25 complex that formed with high affinity, required only the amino-terminal SNARE motif of SNAP25, tolerated a mutation that blocks formation of other syntaxin-SNAP25 complexes, and assembled reversibly when Ca2+ entered cells during depolarization. The complex may represent a precursor to the core complex formed during a Ca2+-dependent priming step of exocytosis.     

Evaluating passive integrated transponder tags for tracking movements of round gobies

Abstract –  The round goby ( Neogobius melanostomus Pallas) is an invasive species in North America and Europe. We evaluated the efficacy of passive integrated transponder (PIT) tags for marking round gobies and tracking their movements with a portable underwater antenna in shallow areas (≤1 m) of a lake. Tagging did not markedly decrease growth of fish <105 mm; however, growth decreased unexpectedly for tagged fish ≥105 mm during the final sampling period. Nevertheless, tagging did not increase mortality regardless of size class, and tag retention was 100% for caged fish. Tagged round gobies in a 20 × 20-m² block net avoided detection by the portable underwater antenna, and a high proportion of fish probably escaped from the net, suggesting that round gobies may be more mobile than previously reported. In conclusion, PIT tags are a viable method for individually marking round gobies, but detecting tagged round gobies with a portable underwater antenna, given current technology, does not appear promising in shallow areas with low habitat complexity.     

Efficacy of a vacuum benthos sampler for collecting demersal fish eggs from gravel substratum

Abstract— We used two densities of eggs (low=900 eggs/m²; high=5100 eggs/m²) in laboratory experiments to estimate the recovery efficiency of the Brown benthos sampler for collecting fish eggs from gravel substrate and to determine if differences (e. g., 5-fold) in egg density in the substratum could be detected with the sampler. The mean egg recovery efficiency of the sampler in the low and high density treatments was 30% (SE=8.7) and 35% (SE=3.8), respectively. The difference between the treatment means was not significant. Therefore, data from the two treatments were pooled and used to estimate the recovery efficiency of the sampler (32.7%, SE=4.4). However, we were able to detect a 5× difference in the number of eggs collected with the sampler between the two treatments. Our estimate of the recovery efficiency of the sampler for collecting fish eggs was less than those reported for the sampler's efficiency for collecting benthic macroinvertebrates. The low recovery efficiency of the sampler for collecting fish eggs does not lessen the utility of the device. Rather, ecologists planning to use the sampler must estimate the recovery efficiency of target fauna, especially if density estimates are to be calculated, because recovery efficiency probably is less than 100%.