Fishing nets - Active fishing gear
Beach seine nets for fisheries research and common use
Profile
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Mgr. Mojmír Vašek, Ph.D. (*1975)
I obtained my doctorate from the Faculty of Science at the University of South Bohemia in České Budějovice. Since 2000 I have worked at the Institute of Hydrobiology (Biology Centre AS CR, v.v.i., Fish Ecology Unit). I have participated in several internships and have conducted field work in several European countries (Netherlands, Austria, Norway, Finland) and in Kenya. My focus is on freshwater ecosystem research, particularly fish ecology and trophic interactions in freshwater environments. I am author or co-author of more than 40 primary research articles published in a variety of notable scientific journals.
Contact: mojmir.vasek@seznam.cz, http://www.hbu.cas.cz/fishecu/
I used fry beach seine nets in the studies mentioned below:
Vašek, M., Kubečka, J., Matěna, J., Seďa, J., 2006. Distribution and diet of 0+ fish within a canyon-shaped European reservoir in late summer. International Review of Hydrobiology 91: 178–194.
Jůza, T., Vašek, M., Kratochvíl, M., Blabolil, P., Čech, M., Draštík, V., Frouzová, J., Muška, M., Peterka, J., Prchalová, M., Říha, M., Tušer, M., Kubečka, J., 2014. Chaos and stability of age-0 fish assemblages in a temperate deep reservoir: unpredictable success and stable habitat use. Hydrobiologia 724: 217–234.
Fry beach seine nets – used for fry and juvenile fish sampling
- in lakes, reservoirs, ponds and slow moving rivers
- common net length – 10 or 20 m, height 2 or 3 m
- 2 mm mesh size (using 4 mm mesh in late summer possible)
Fry beach seine nets are suitable for sampling fish in near shore areas with gently sloped banks. The bottom must be free of structures (stones, stumps, branches, macrophytes). Beach seine nets are most effective on gravel, sandy and clay beaches.
Haul technique
Casting a fry beach seine net
casting from boat – in deeper sampling locations (fish disturbance minimalized)
Casting by wading – in shallow sampling locations
Methods of hauls
- water - water
Net is casted parallel to the shore and afterwards hauled by pulling ropes to the shore.
- shore-shore
Net is casted in half-circle from shore to shore and then closed around the sampled site
Haul is performed by 2 – 4 people distributed evenly on both ends of the beach seine net. Pressing lead line to the bottom is necessary during net hauling.
Advantages of a fry beach seine net
- affordable
- easy to manipulate
- highly efficient in suitable sampling sites
- harmless to fish – does not cause damage
- simple catch evaluation
- easy to calculate abundance of fish occurring in littoral area of water body
Profile
Mgr. Milan Říha, Ph.D.
I studied in the Faculty of Science at the University of South Bohemia in České Budějovice and have worked at the Institute of Hydrobiology (Biology Centre AS CR, v.v.i., Fish Ecology Unit) since 2004. My research is conducted mainly in the Czech Republic and other European countries such as Austria, Spain, and the Netherlands. I have also conducted research in North America, particularly Puerto Rico and USA (fish distribution in Lake Ontario). My main research topics are fish distribution in freshwater ecosystems and research methodology – particularly the development and usage of active fishing gear (beach seine nets and trawls). I co-operate closely with the Pokorný-sítě company on their development. I have authored or co-authored 30 primary research articles that have been published in several high impact journals.
Contact: mriha00@gmail.com, http://www.fishecu.cz/staff-members/riha/
Adult beach seine nets
beach seine nets are essential for sampling shallow littoral areas
species and size selectivity of beach seine net is very low in both day and night
beach seine nets are highly suitable for quantitative sampling
beach seine nets provide real values about the amounts of most species and size categories in sampled areas
beach seine nets 100 m or longer are effective tools for biomanipulation purposes
Usage
- sampling of various species and sizes
- sampling in lakes, reservoirs, ponds and slow flowing rivers
- recommended length of 100 or 200 m with a minimum height of 4 m for hauling shore-shore
- recommended length of 50 m with a minimum height of 4 m for hauling water-water
- minimum net length 20 m
- 10 mm mesh size – fish one year and older are usually not able to pass through this mesh size
Beach seine net casting
water-water
The whole net is deployed at the targeted distance along the shoreline and hauled towards the shore.
The disadvantage of this technique is the large amount of fish escaping through the gaps between the net and shore
Sampled area calculation
- the sampled area is the shape of a regular trapezoid with dimensions:
- a = length of used net
- c = approximately 2/3 of used net
- v = casting distance from the shore
The sampled area is then calculated according to a formula:
Shore - shore
This technique is optimal for quantitative sampling
The net is cast in a rectangle from shore to shore – the net encloses the sampled area
The sampled area depth must not exceed the height of the beach seine net
Under these conditions the net prevents fish from escaping
Sampled area calculation
- the sampled area is rectangle-shaped or square-shaped
- the values needed for calculation:
- length of the net casted parallel to the shore (a)
- length of the net cast perpendicular to the shore (b) - the calculation is based on the formula for the area of a square
Colored floats placed every ten meters help to measure lengths of cast net.
It is possible to use the counting of floats during net casting to calculate the sampled area.
- After calculation, it is possible to compute the catch to the hectare or another required area unit.
- More details about beach seine net usage are found in Říha et al. (2008) and Kubečka et al. (2010). (http://www.fishecu.cz/staff-members/riha/)
