A marking technique for live fish eggs and larvae

 A new marking technique for live fish eggs and larvae was proposed to elucidate the larval biology and adult breeding ecology of wild fish. In the laboratory, females of a freshwater goby Rhinogobius sp. OR were abdominally injected with one of three coloring agents—brilliant blue FCF, rose Bengal, or β-carotene—before their oviposition. The rose Bengal proved lethal to adult fish. The other two dyes had little effect on adult mortality. With these two treatments, there were negative effects on neither fecundity nor egg mortality, resulting in normally developed larvae. The brilliant blue FCF stained eggs and larvae greenish blue whereas the staining effect of β-carotene was unclear. The timing of injection was important in effective staining of eggs and reducing the risk of miscarriage. In conclusion, the brilliant blue FCF was the more useful marker. We discuss what this method can show us about the ecology of wild fish and how this method can be applied to field study. Received: March 6, 2002 / Revised: July 11, 2002 / Accepted: August 14, 2002 RID="*" ID="*" Present address: Center for Marine Environmental Studies, Ehime University, 3 Bunkyo-cho, Matsuyama 790-8577, Japan (e-mail: nokuda@sci.ehime-u.ac.jp) Acknowledgments I am grateful to K. Karino, M. Kohda, and A. Moriyama for giving us valuable advice and to M. Inoue and H. Miyatake for their field assistance. This study was financially supported by Research Fellowships of the Japan Society for the Promotion of Science for Young Scientists. Correspondence to:Noboru Okuda     

A folding artificial substratum sampler for use in standing water

A new easily retrieved folding artificial substratum sampler is described and its performance compared with that of trays in Cow Green Reservoir at a depth of 15–18 m.     

A microbial sampler for freshwaters

A freshwater sampler using five sterile evacuated glass tubes is described. Water enters when a rubber stopper is mechanically removed from the end of a sterile hypodermic needle inserted into each tube. Plate counts of bacterial colonies were compared with those obtained with other samplers.     

A microgradient sampler for shallow waters

Summary A cheap, light and simple device is described for the sampling of physico-chemical microgradients in the free-water zone of shallow water bodies. The sampler is commercialized by ATS, Mariastraat 42, The Hague, The Netherlands.Publication no. 179 of the Delta Institute for Hydrobiological Research.     

A core sampler for semi-fluid substrates

Summary A core sampler developed for use in sampling water-filled tree-holes is described. This apparatus consists of an auger mechanism that fits inside the conventional corer tube. Its construction is simple and inexpensive and the resulting instrument is both portable and easy to use. Resumen Una descripción de un tubo saca-testigos dise?ado para tomar muestras en cavidades de árboles conteniendo agua es presentada. El aparato consiste de un mecanismo taladrante que se ajusta dentro del tubo del saca-testigos convencional. Su construcción es simple y barata, y el instrumento es portátil y fácil de usar.     

A quantitative sampler for air-breathing aquatic insects

SUMMARY. A quantitative funnel-trap sampler for air-breathing aquatic insects is described. Performance tests with special reference to adult Glaenocorisa propinqua are presented. Abundance was calculated from pilot surveys with the funnel-trap sampler during 1976 and compared with results from a trial with the capture-recapture method. The influence of temperature on the frequency with which adult Glaenocorisa propinqua renews the bubble gilt was measured.     

Development of a gut perfusion model as an alternative to the use of live fish

An alternative fish model with the principal aim of studying the interaction between fish pathogens and the intestinal tissue was developed. The preparation consisted of an excised gut tractus from rainbow trout (Oncorhynchus mykiss), perfused through cannulation of the aorta intestinalis ventralis with filtered and heparinized Cortland+dextran 1% as the perfusion fluid. This perfusion fluid was delivered by means of a drip. The perfused gut tractus was suspended in a circular bath filled with Ringer solution, which was aerated and kept at a constant temperature of 12 degrees C. Unperfused gut placed in Ringer solution at the same temperature served as the negative control. Perfusion was effective in maintaining the gut in a healthy condition for at least 60 min with only slight oedema and sloughing of the epithelium. Conversely, the unperfused gut revealed excessive tissue degeneration and severe necrosis.     

A portable suction sampler for rock epibiota

Summary 1. A fully portable suction sampler which can be operated by one diver is described.2. Rock epibiota is removed by a scraper tube which leads, through a collecting chamber, to an air-lift suction chamber and tube. The sample is held in a net bag before reaching the suction chamber. Air is supplied by a cylinder incorporated into the unit.3. The sampler removes all epilithic biota except for the parts of encrusting species cemented to the rock.4. The sampler can also be used for sand fauna.

---

Ein tragbarer Saugsammler für epibiotisch auf Felsen lebende Organismen

Kurzfassung Eine Saugpumpe für bestandskundliche Untersuchungen, die von einem Taucher getragen und bedient werden kann, wird beschrieben. Sie besteht aus einer Sammelkammer, in die zwischen dem Schabrohr und der Luftsaugkammer ein Sammelnetz eingefügt wird. Die Saugkammer ist durch ein Reduktionsventil mit einem Preßluftzylinder verbunden. Mit Hilfe dieses Sammelgeräts lassen sich fast alle Organismen von Felsoberflächen entfernen. Es kann überdies auch zur quantitativen Erfassung der Fauna auf Sandböden eingesetzt werden. Vor- und Nachteile dieses Gerätes werden diskutiert.

     

A portable pump sampler for lotic periphyton

A sampling technique for collecting lotic periphyton on sedimentary substrates using a peristaltic pump is described. Quantitative samples of periphyton standing crop and colonization rate are collected by the same procedure. The technique eliminates human disturbance problems associated with floating artificial samplers by establishing permanent sampling sites directly on submerged substances.     

Seasonality and heterogeneity of live fish movements in Scottish fish farms

Movement of live animals is a key contributor to disease spread. Farmed Atlantic salmon Salmo salar, rainbow trout Onchorynchus mykiss and brown/sea trout Salmo trutta are initially raised in freshwater (FW) farms; all the salmon and some of the trout are subsequently moved to seawater (SW) farms. Frequently, fish are moved between farms during their FW stage and sometimes during their SW stage. Seasonality and differences in contact patterns across production phases have been shown to influence the course of an epidemic in livestock; however, these parameters have not been included in previous network models studying disease transmission in salmonids. In Scotland, farmers are required to register fish movements onto and off their farms; these records were used in the present study to investigate seasonality and heterogeneity of movements for each production phase separately for farmed salmon, rainbow trout and brown/sea trout. Salmon FW-FW and FW-SW movements showed a higher degree of heterogeneity in number of contacts and different seasonal patterns compared with SW-SW movements. FW-FW movements peaked from May to July and FW-SW movements peaked from March to April and from October to November. Salmon SW-SW movements occurred more consistently over the year and showed fewer connections and number of repeated connections between farms. Therefore, the salmon SW-SW network might be treated as homogeneous regarding the number of connections between farms and without seasonality. However, seasonality and production phase should be included in simulation models concerning FW-FW and FW-SW movements specifically. The number of rainbow trout FW-FW and brown/sea trout FW-FW movements were different from random. However, movements from other production phases were too low to discern a seasonal pattern or differences in contact pattern.     

A diver-operated quantitative bottom sampler for sand macrofaunas

Summary 1. A new bottom sampler for macrofauna is described which is easily operated by a diver.2. The airlift pump principle is employed firstly to sink a sampling cylinder into the seabed and secondly to operate a suction pipe which is used to excavate sand and animals from within the cylinder.3. The sampler covers an area of 0.1 m² and penetrates to a depth of 60 cm. It is particularly suitable for quantitative studies of deeper burrowing fauna (e. g.Ensis spp. andLutraria spp.).4. The sampler is designed for use in sandy sediments and for studies on the distribution of faunas within small areas where line transects or grids of samples are required.

---

Ein vom Taucher betätigtes Gerät zur quantitativen Entnahme der Makrofauna auf Sandböden

Kurzfassung Zur Entnahme quantitativer Proben der Makrofauna aus festem Sandboden gibt es nur zwei Geräte, die beide sehr schwer sind und einer kräftigen Winde auf einem großen Schiff bedürfen: (a) der Knudsengreifer (0,1 m² Fläche, 30 cm Einstichtiefe, 150 kg) und (b) der Kastengreifer von Reineck (20×30 cm Fläche, 40 cm Einstichtiefe, 750 kg). Für Untersuchungen über die Verteilung benthischer Makrofauna innerhalb kleiner Gebiete war jedoch ein Gerät zur Entnahme von Bodenproben erwünscht, das von einem Taucher gezielt eingesetzt werden kann. Eine Sammeltiefe von mehr als 30 beziehungsweise 40 cm war erforderlich, um den Fang der tiefer grabenden Arten, beispielsweise der MuschelLutraria, zu gewährleisten. Das neue Gerät wurde zweiteilig entworfen. Der eine Teil besteht aus einem offenen Stahlzylinder, der eine Länge von 60 cm und eine Grundfläche von 0,1 m² aufweist. Er wird zunächst mit Handkraft senkrecht in den Boden hineingepreßt, damit er vom Sand gut abgedichtet wird. Das obere Ende wird anschließend mit einem Deckel verschlossen, und das Wasser, das sich im Zylinder oberhalb des Sedimentes befindet, wird durch eine Pumpe abgesogen. Der hydrostatische Druck auf den Deckel preßt den Zylinder in den Sand. Wenn der Zylinder völlig in das Sediment versenkt ist, wird der Deckel entfernt und der vom Zylinder umfaßte Sand durch den zweiten Teil des Gerätes ausgesaugt. Dieser besteht aus einer langen Kunststoffröhre von etwa 8 bis 10 cm Durchmesser. Sie wird in senkrechter Stellung völlig unter Wasser gehalten. Wird Luft unter Druck in das untere Ende eingeleitet, so funktioniert die Röhre als eine Lufthebepumpe. Ein speziell gebautes Sieb ist am oberen Ende des Steigrohres befestigt. Der Taucher führt das untere Ende dieser Saugpumpe in den Zylinder und saugt dessen Inhalt in das Sieb hinein. Die Druckluft für die Betätigung des Instrumentes wird von einem Kompressor oder aus Druckluftflaschen (4–5 m³) geliefert. Das beschriebene Gerät ist leicht und kann deshalb mühelos vom Taucher bedient werden. Es kann von Kleinbooten aus eingesetzt werden und benötigt keine Winde.

     

A vacuum benthos sampler suitable for diverse habitats

The vacuum benthos sampler consists of a vacuum chamber equipped with a collecting net connected to the intake of a 12 volt pump, a battery, and a standpipe. Contents of the standpipe are vacuumed while substrate is removed and washed with the exhaust hose. The vacuum chamber is designed for rapid changing of nets during replicate sampling. This sampler is equally efficient in flowing and standing water. It was more effective than a modified Hess sampler for collecting a large variety of benthos from flowing (ca 0.25–0.75 m/s) riffles. Required operation time is variable, but 93% of invertebrates caught in 10 min were captured in the first 5 min during our tests, and there was a 94% mean recovery of released organisms during 10 min of subsequent operation. Advantages over previous suction samplers include interception of organisms before they pass through a pump, return of outlet water to the standpipe, capability of sampling in shallow (20–30 mm) water, and that it can be carried and operated by one person.     

A simple syringe sampler for sampling bottom waters

SUMMARY. A cheap messenger-operated device for sampling water immediately above sediment is described.     

Impacts of the live reef fish trade on populations of coral reef fish off northern Borneo

The live reef fish trade (LRFT) is one of the greatest but least-quantified sources of fishing pressure for several species of large coral reef fish across the Indo-Pacific. For the first time we quantify the localized impact of the LRFT. We collected data from three LRFT traders in northern Borneo, which yielded information on daily fishing effort and the species and mass of all fishes sold every day by individual fishers or vessels over 2, 3 and 8 years. Total monthly catch and relative abundance (catch-per-unit-effort) declined significantly in several species, including the most valuable species the Napoleon wrasse (Cheilinus undulatus, estimated changes of -98 and -78% over 8 years in catch and relative abundance, respectively) and lower-value bluelined groupers (Plectropomus oligocanthus: -99 and -81%) and Epinephelus groupers (-89 and -32%). These severe declines were rapid, species-specific and occurred in the first 2-4 years of the dataset and are, we believe, directly attributable to the LRFT. This has crucial implications for future data collection and monitoring if population collapses in other parts of the LRFT and similar wildlife trades are to be successfully detected.     

Quantitative evaluation of the point method for fish stomach contents analysis

To test the accuracy of the point methods a simulation was conducted using simulated stomachs. Results from seven participants told to analyse the stomachs by the point and percentage methods differed considerably among subjects and from the control.