Water quality - Guidance on the scope and selection of fish sampling methods

This document defines methods for sampling fish and procedures for selection of methods in order to evaluate fish populations in rivers, lakes and transitional waters. A selected literature with references in support of this document is given in the bibliography. This document refers to the standards "Water quality - Sampling of fish with electricity" (EN 14011) and "Water quality - Sampling of fish with multi-mesh gillnets" (EN 14757).

Wasserbeschaffenheit - Anleitung zur Anwendung und Auswahl von Verfahren zur Probenahme von Fischen

Qualité de l'eau - Guide sur le domaine d'application et la sélection des méthodes d'échantillonnage de poissons

La présente Norme européenne décrit les méthodes d'échantillonnage des poissons et les modes opératoires pour la sélection des méthodes afin d'évaluer les populations de poissons dans les rivieres, les lacs et les eaux de transition. La bibliographie contient une sélection de textes avec des références venant a l'appui de la présente norme. Ce document fait référence aux normes " Échantillonnage des poissons a l'électricité " (EN 14011) et " Échantillonnage des poissons a l'aide de filets maillants " (prEN 14757, en cours de préparation).

Kakovost vode – Navodilo za področje uporabe in izbiro metod vzorčenja rib

General Information

Status
Published
Publication Date
30-Jun-2006
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
01-Jul-2006
Due Date
01-Jul-2006
Completion Date
01-Jul-2006

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2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Water quality - Guidance on the scope and selection of fish sampling methodsQualité de l'eau - Guide sur le domaine d'application et la sélection des méthodes d'échantillonnage de poissonsWasserbeschaffenheit - Anleitung zur Anwendung und Auswahl von Verfahren zur Probenahme von FischenTa slovenski standard je istoveten z:EN 14962:2006SIST EN 14962:2006en,fr,de65.15013.060.70ICS:SLOVENSKI

STANDARDSIST EN 14962:200601-julij-2006

EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN 14962April 2006ICS 13.060.70 English VersionWater quality - Guidance on the scope and selection of fishsampling methodsQualité de l'eau - Guide sur le domaine d'application et lasélection des méthodes d'échantillonnage de poissonsWasserbeschaffenheit - Anleitung zur Anwendung undAuswahl von Verfahren zur Probenahme von FischenThis European Standard was approved by CEN on 16 March 2006.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the Central Secretariat or to any CEN member.This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the officialversions.CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania,Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre: rue de Stassart, 36

B-1050 Brussels© 2006 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 14962:2006: E

EN 14962:2006 (E) 2 Contents Page Foreword..............................................................................................................................................................3 Introduction.........................................................................................................................................................4 1 Scope......................................................................................................................................................5 2 Normative references............................................................................................................................5 3 Terms and definitions...........................................................................................................................5 4 Principle..................................................................................................................................................6 5 Categories of rivers, lakes and transitional waters............................................................................6 6 Fish sampling.........................................................................................................................................7 7 Selection of sampling methods..........................................................................................................23 Bibliography......................................................................................................................................................24

EN 14962:2006 (E) 3 Foreword This document (EN 14962:2006) has been prepared by Technical Committee CEN/TC 230 “Water analysis”, the secretariat of which is held by DIN. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by October 2006, and conflicting national standards shall be withdrawn at the latest by October 2006.

According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.

EN 14962:2006 (E) 4 Introduction This document is developed to select appropriate fish sampling methods for the evaluation of the species composition, abundance and age structure of fish in rivers, lakes and transitional waters. WARNING — Persons using this document should be familiar with normal laboratory practice. This document does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user to establish appropriate safety and health practices and to ensure compliance with any national regulatory conditions. IMPORTANT — It is absolutely essential that tests conducted according to this document be carried out by suitably trained staff.

EN 14962:2006 (E) 5 1 Scope This document defines methods for sampling fish and procedures for selection of methods in order to evaluate fish populations in rivers, lakes and transitional waters. A selected literature with references in support of this document is given in the bibliography. This document refers to the standards “Water quality - Sampling of fish with electricity” (EN 14011) and “Water quality - Sampling of fish with multi-mesh gillnets” (EN 14757). 2 Normative references Not applicable 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 river natural body of water flowing continuously or intermittently along a well-defined course into an ocean, sea, lake, inland depression, marsh or other water-course [ISO 6107-2:1997] NOTE A body of inland water flowing for the most part on the surface of the land but which may flow underground for part of its course (Directive 2000/60/EC) 3.2 lake inland body of water of considerable area [ISO 6107-2:1997] NOTE A body of standing inland surface water (Directive 2000/60/EC). 3.3 transitional water body of surface water in the vicinity of river mouths which are partly saline in character as a result of their proximity to coastal waters but which are substantially influenced by freshwater flows (Directive 2000/60/EC) 3.4 water categories rivers and transitional waters are categorized according to width and maximum depth, and lakes are categorised according to area and the presence or absence of a pelagic or profundal zone NOTE Other categories may be used in limnological science or other standards. 3.5 fish habitat place where the fish is to be sampled 3.6 species composition species list from the target water which may include the relative dominance (number of fish of species A in relation to the total number of fish of all species [100 % ⋅ NA/NTot])

EN 14962:2006 (E) 6 3.7 fish abundance total number of fish of species A (NA) per water area (NA /m2, NA /ha), water volume (NA /m3) or river or bank length (NA /m, NA /100 m); the catch per unit of effort (CPUE) as an index of abundance may also be used NOTE CPUE is the catch of fish, in numbers or in weight, taken by a definite unit of fishing effort. The effort can be the number of nets set during the night, the length of a stretch sampled by electrofishing etc. 3.8 age structure number (NAi) or relative number (100 % ⋅ NAi /NA) of fish of species A in age group i NOTE Age groups may be derived by age determination of fish from e.g. reading scales or from length-frequency data. 4 Principle In order to evaluate the population parameters, species composition, abundance and age structure of fish populations in rivers, lakes and transitional waters, appropriate sampling methods are required. The appropriate sampling method depends on the objective itself as well as on the water type and category, the target fish species and their body length. Sampling methods are selected with respect to the broad variety of inland waters and to the diversity of species and their habitats. The suitability of the given methods was classified in order to achieve a valid evaluation. Their applicability for routine monitoring was taken into account. 5 Categories of rivers, lakes and transitional waters For the appropriate use of fish sampling methods rivers, lakes and transitional waters have been categorized. The different water categories were selected for the purpose of this standard independent of other categories used in the terminology of limnological science or other standards. Categories for rivers and transitional waters are not defined directly by water velocity, although water velocity is partly depending on river width and depth. However, sampling methods should be chosen to be appropriate for the specific water velocity in the river (see also 6.4, Table 4). The categories are as follows: Table 1 — Categories for rivers Category Width max. Depth

m m River category 1 (brook) < 5 < 1 River category 2 > 5 < 2 River category 3 < 30 > 2 River category 4 30 to 100 > 2 River category 5 > 100 > 2

EN 14962:2006 (E) 7 Table 2 — Categories for lakes Category Presence or absence of a pelagic or profundal zone Area

km2 Lake category 1 With or without a pelagic or profundal zone < 0,5 Lake category 2 Without a pelagic or profundal zone > 0,5 Lake category 3 With a pelagic and profundal zone > 0,5 Table 3 — Categories for transitional waters Category Width max. Depth

m m Transitional water category 1 < 5 < 1 Transitional water category 2 > 5 < 2 Transitional water category 3 < 30 > 2 Transitional water category 4 30 to 100 > 2 Transitional water category 5 > 100 > 2

Within a river or transitional water, categories according to the Tables 1 and 3 usually change from lower to higher ones according to longitudinal changes. But also within a relatively short stretch of a river or transitional water, categories can change from lower to higher ones and vice versa. In this case, the area itself of a river or transitional water, and not the whole river or transitional water, should be classified according to the given categories. 6 Fish sampling 6.1 General Sampling methods are separated into methods by capture (6.2) and data sampling without fish capture (6.3). The principles are explained and the target water types or categories and fish species are given. The suitability of the methods is evaluated depending on the different water categories and their habitats as well as the target species. Target species are those species which can efficiently be caught by a particular method. Tables 4 to 6 provide a synopsis on sampling methods suitable or useful for the determination of the population parameters. Methods not described below may be used in order to obtain additional information. They shall not be used exclusively. 6.2 Fish sampling by capture 6.2.1 Principle of fish capture Fish may be caught by active gear (6.2.2 to 6.2.4) or passive (6.2.5 to 6.2.10). For all gear seasonal aspects shall be taken into account. The efficiency of active gear (electric fishing, seining, trawling) especially may vary considerably depending on the time (day/night) of use. Active gear is characterized by a comparatively short-term use, whereas passive ones normally are exposed over longer time periods. The fishing devices used shall be adapted to the local conditions as well as to the expected fish community. If it is intended to

EN 14962:2006 (E) 8 determine the species composition and age structure, an adaptation of fishing gear mesh size(s), day time and season of exposure is required. In order to determine species composition and fish abundance of a certain water body the analysis of professional or non-professional fishery statistics1) may be considered as suitable, providing the statistics are based on binding regulations. Whether such types of statistics can be used or not, depends on the reliability and exactness of the fishermen’s records. In order to estimate fish abundance from fisheries statistics, information on fishing effort has to be included. The age structure shall be determined by additional sampling. Professional fishermen do not necessarily fish on all species occurring. Here species composition, fish abundance and age structure of the professionally unfished species shall be determined by additional sampling. 6.2.2 Electrofishing 6.2.2.1 General Electricity is led into the water by a special apparatus and fish are caught by the anodic effect (galvanotaxis). Catching fish with electricity is restricted to relatively shallow areas and to stretches of transitional waters with a relatively low conductivity (γ < 6 mS/cm). Electrofishing can be carried out by wading or from a boat. Electric fishing is described in the standard “Sampling of fish with electricity” (EN 14011). 6.2.2.2 Electrofishing by wading Principle: For electrofishing by wading a backpack, other portable device or a generator placed at the bank or in a boat is used. The member(s) of staff using one or more anodes wades/wade through the water and covers/cover all relevant fish habitats. Water types and categories: Electric fishing by wading can be carried out in rivers or transitional waters, categories 1 and 2 and in the littoral zone of larger rivers, transitional waters and lakes, where wading is possible without any risk. Target species: All fish species and sizes living in the areas can be caught. Suitability: Electrofishing is highly suitable for rivers categories 1 and 2, where the whole width of a river can be covered by one or more anodes. The efficiency can be increased by using stop nets at the beginning and at the end of the target zone and by multiple fishing runs. Due to the relatively high conductivity electric fishing is only of medium suitability for transitional waters. Under the conditions described above, samples for species composition, fish abundance and age structure can be collected. 6.2.2.3 Electrofishing from a boat Principle: A generator in combination with the required equipment is placed in a boat, sometimes also on the bank, and the member(s) of staff fish from the boat. Water types and categories: Electric fishing from a boat is possible in rivers where the max. depth does not exceed 2 m and at the relatively shallow sides near the banks and shorelines of deeper rivers, lakes and transitional waters with γ < 6 mS/cm. With adjusted electrofishing equipment the depth range may be extended up to a water depth of 3 m beside the banks or shorelines [27]. Target species: All fish species and sizes which stay in the areas described can be sampled.

1) For the use of angling statistics see 6.2.10.

EN 14962:2006 (E) 9 Suitability: The efficiency is high in category 2 rivers. It may be increased by using stop nets. This method is also highly suitable for the littoral habitats of deeper rivers and lakes up to a maximum depth of 2 m. Electric fishing in other regions of deeper waters may be useful only to obtain additional information on species composition. Trammel nets set parallel to the bank of the target study stretch can be used to catch fish trying to escape into deeper zones. Generally, electric fishing cannot be carried out successfully in the middle of rivers or lakes, maybe with the exception of category 3 rivers. Such fishing may be useful only to complete samples on species composition obtained by other methods. 6.2.3 Seines 6.2.3.1 General An area is surrounded with a net and pulled through. The enclosed fish are forced to flee towards the cod-end2) or a net bag from where they can be removed. Several types of seines may be used for sampling fish in lakes, rivers or transitional waters. 6.2.3.2 Beach seine Principle: Seining in the littoral, non vegetated zone using nets mostly < 50 m in length, < 3 m in height and mesh size preferably < 10 mm. The whole water column from bottom to surface can be sampled. The seine is pulled towards the bank by hand. Water types and categories: Generally, beach seines can be used in littoral habitats of deeper rivers or transitional waters cat. 3 to 5 as well as lakes. A beach seine may also be used in transitional waters categories 1 and 2 in order to complete samples obtained by electrofishing. Target species: Many species, especially their juveniles, are recorded. Suitability: Beach seines are especially useful in order to determine natural reproduction and in waters where electric fishing is difficult or impossible. 6.2.3.3 Normal (bottom) seine Principle: Seining in deeper areas using nets mostly > 50 m in length, > 3 m in height and mesh size > 10 mm in the cod-end or the central panel. The mesh sizes of the net walls of a seine are normally larger than those in the cod-end. The whole water column can be sampled. The seine is pulled with ropes towards a bank, but can also be pulled into a boat. Normal seines are moved by manpower or by engine power. Water types and categories: Normal seines can be used in lakes, rivers (cat. 3 to 5) or transitional waters (cat. 3 to 5) with a relatively even bottom without underwater obstacles. The height of the seine shall be adapted to the depth of the target water or zone. Target species: The mesh size of the cod-end or the central panel of the seine affects the species and size distribution of the catch. Therefore it may be difficult to catch juveniles and small species. Suitability: The length of a seine can be up to a few hundred meters, and accordingly a relatively large area can be surrounded. Fish abundance or at least a CPUE can often be estimated. Depending on the mesh size of the cod-end only fish exceeding a certain size can be caught. The samples on species composition and age structure from the respective area should be completed by samples collected with other methods. 6.2.3.4 Pelagic seine (Purse seine) Principle: Pelagic seines are mostly used in deeper lakes and samples are taken from the upper water layers. Purse seines can be hundreds of metres in length and several metres in height.

2) The cod-end is a long-stretched net bag at the end of a seine or a trawl.

EN 14962:2006 (E) 10 Water types and categories: Pelagic seines are useful in large and deeper lakes (category 3). Sometimes, pelagic seines may be used in small lakes (category 1) for special purposes. Target species: All species and stages which occur regularly in the pelagic habitat can be sampled. Suitability: Pelagic seines are highly suitable for estimating fish abundance or at least CPUE and the determination of species composition. If the age structure shall be determined additionally, mesh sizes shall be adapted or the pelagic seine shall be combined with other methods. Pelagic seines are also suitable in combination with other methods where species identification is necessary. 6.2.4 Trawls and push net 6.2.4.1 General Trawling is carried out by pulling a funnel-shaped trawl net with either one or two boats (vessels). The size of a trawl can vary from small experimental trawls to larger commercial trawls. The speed during trawling affects catching efficiency. Species composition and size distribution depend on the mesh size of the cod-end of the trawl. For special purposes, e.g. the capture of larvae and juveniles, funnel-shaped nets are pushed beside or in front of a boat (push net). 6.2.4.2 Bottom trawl Principle: Bottom trawls are pulled on the bottom by one or two vessels over a definite distance. The riverbed or the lake bottom should be relatively even. In rivers with moderate or relatively high current, the trawl is pulled upstream, seldom downstream. Water types and categories: Appropriate water types and categories are rivers (cat. 3 to 5), lakes (cat. 2 to 3) and transitional waters (cat. 3 to 5). Target species: All fish species and sizes occurring in the habitat can be sampled. Suitability: Bottom trawls are highly suitable in larger rivers and transitional waters cat. 4 to 5 as well as lakes (cat. 2 to 3) where species composition, abundance and age structure can be determined. In smaller rivers (cat. 3) other sampling methods seem to be more efficient. 6.2.4.3 Pelagic trawl Principle: The trawl can be pulled by one or two vessels at any depth. An experimental survey can consist of a few trawls taking samples in different water depths. Water types and categories: The pelagic zone of large and deep lakes (cat. 3) is the preferred area for the use of pelagic trawls. Target species: All species occurring regularly in the pelagic zone are to be found in pelagic trawl samples. Suitability: Pelagic trawling is highly suitable for determining species composition and estimating fish abundance. If the age structure shall be determined additionally, mesh sizes have to be adapted. Sampling by trawling can be combined with echo sounding. 6.2.4.4 Push net Principle: Funnel-shaped nets are fixed beside or in front of a boat and pushed through the water. Water types and categories: Push nets may be used near the surface of lakes as well as rivers and transitional waters cat. 4 to 5.

EN 14962:2006 (E) 11 Target species: Larvae and early juveniles are sampled by push nets. Suitability: Push nets are useful in order to sample near-surface water layers to obtain additional information on the age structure. 6.2.5 Gill nets and trammel net 6.2.5.1 General Both gill nets and trammel nets are entanglement equipment consisting of one (gill net) or three (trammel net) net panels. Fish are wedged, gilled or tangled. Gill nets are widely used both in commercial and experimental (scientific) fisheries. They can be used as bottom, pelagic, vertical or drift nets. According to the target species and sizes nets with different mesh sizes shall be used, either as single or multi-mesh nets. The standardised sampling of fish in lakes with bottom and pelagic multi-mesh gill nets is described in the standard “Sampling of fish with multi-mesh gillnets” (EN 14757). Trammel nets are bottom nets which are used for special purposes or under certain circumstances. 6.2.5.2 Bottom gill net Principle: Bottom gill nets are set on the lake bottom or riverbed. They may be fixed or anchored. Water types and categories: Bottom gill nets are mainly used in the lentic zone of rivers and transitional waters cat. 3 to 5 and in all parts of lakes. Target species: Most of the species using the littoral or profundal zone can be sampled. Species with eel-like morphology and some bottom dwelling species are regularly underrepresented, whereas some species may be overrepresented due to morphological characteristics. Suitability: Bottom gill nets are highly suitable for the determination of species composition and age structure as well as for estimating fish abundance. In rivers and transitional waters, sampling with bottom gill nets may complete the samples on the population parameters gathered by other sampling methods. 6.2.5.3 Pelagic gill net Principle: Pelagic gill nets are floating on the surface or in a definite depth of the water column. They may be anchored or not. Water types and categories: Pelagic gill nets can be used in deeper lakes in order to sample the pelagic habitat. Target species: All species and sizes living in the pelagic habitat can be sampled. Suitability: Gill nets with different mesh sizes are highly suitable for determining species composition and age structure and for estimating fish abundance. 6.2.5.4 Vertical gill net Principle: Vertical gill nets can sample the complete water depth (usually from 1 m to 80 m). The devices are 2 m wide and rolled tightly on PVC tubes which also act as floats. They usually consist of multi-mesh sets and can be used as pelagic or bottom nets. Water types and categories: Vertical gill nets can be used in the pelagic or littoral parts of lakes and in rivers with low or no current. Target species: All species and sizes living in the pelagic or littoral habitat can be caught.

EN 14962:2006 (E) 12 Suitability: Vertical gill nets are highly suitable for determining species composition and age structure and for estimating fish abundance. In rivers and transitional waters, sampling with vertical gill nets may complete the samples on the population parameters gathered by other sampling methods. 6.2.5.5 Drift net Principle: Gill nets drift and are carried along by the current. Water types and categories: Drift nets can be used in deeper areas in the middle of rivers or transitional waters, but also in shallow stretches where the nets can drift close to the bottom. Target species: Specimens which inhabit the upper water layers of larger rivers can be caught with drift nets. Suitability: Drift nets can be used as an additional method to complete the samples for species composition and age structure in certain areas. 6.2.5.6 Trammel net Principle: Trammel nets consist of one small mesh sized net panel in the middle and two larger mesh sized net panels outside. Water types and categories: Trammel nets may be used in littoral habitats of rivers or transitional waters with low current as well as in most parts of lakes. Target species: Most species can be sampled with trammel nets depending on the mesh sizes of the net walls. Especially larger sizes are caught. Suitability: Trammel nets are useful for determining species composition and estimating abundance. 6.2.6 Anchor nets 6.2.6.1 General Anchor nets (gape nets, stow nets) are entrapment equipment which are set in larger rivers towards the current and anchored. The mouth of the net is kept open by a frame, by two beams or by otter boards. Migrating fish or those moving with the current are captured. The mesh size of the cod-end affects the species composition and the size distribution. 6.2.6.2 Anchor net fixed at a bank Principle: One wing of the anchor net is fixed at a bank, while the other one is connected to an otter board which keeps the mouth open. Water types and categories: Anchor nets operated from a bank are useful in larger rivers or transitional waters cat. 4 to 5. Target species: All species living in the habitat can be sampled, but especially migrating or moving species can be caught. Suitability: Anchor nets are highly suitable for larger rivers or transitional waters cat. 4 to 5. The use of such anchor nets seems to be appropriate only when operated by professional fishermen. 6.2.6.3 Anchor net used from a vessel Principle: An anchor net (stow net) is operated from a vessel which is anchored in the river. The mouth of the net is kept open by a frame or an upper and an under beam.

EN 14962:2006 (E) 13 Water types and categories: This type of anchor net can be used in larger rivers or in transitional waters cat. 4 to 5. Although in commercial fisheries mostly the mid-water habitat is fished the under beam can also be placed close to the bottom. Target species: All species and sizes living in the habitat can be sampled. Especially migrating or moving species can be caught. Suitability: Anchor nets from a vessel are highly suitable for rivers or transitional waters cat. 4 to 5 to evaluate species composition, fish abundance and age structure. Its use seems appropriate only when operated by professional fishermen. In order to sample small sized species or juveniles the mesh size has to be adapted. 6.2.7 Traps 6.2.7.1 General Fish enter entrapment gear (basket, fyke or trap net) through a specially constructed entrance. Entrapment gear exists in a broad variety. They are used in lakes as well as in rivers or transitional waters with low current or in backwaters. Instream traps are installed in fish ways, fish ladders or at weirs and fish are guided into the trap. The mesh size of the traps affects the species composition and size distribution. The use of entrapment gear is suitable only long-term during representative periods. 6.2.7.2 Basket Principle: Fish enter this type of gear by seeking shelter, by being attracted by the presence of bait or by moving along the shoreline or special structures of the water bottom. Water types and categories: Baskets are used in lakes and backwaters of rivers, seldom in fast flowing rivers or transitional waters. Target species: Bottom dwelling species may be the target species. Suitability: Baskets may be useful to obtain additional information on bottom dwelling species. 6.2.7.3 Fyke net Principle: Fyke nets are similar to baskets and the net is distended by hoops or frames. Mostly they are substantially larger than baskets, and equipped with a net lead. Sometimes wings are attached at the entrance. Water types and categories: Fyke nets are preferably used in the littoral habitats of lakes, but may also be used in rivers or transitional waters in areas with low current or in backwaters. Target species: All fish species and sizes occurring in the habitat can be sampled. Suitability: Fyke nets are highly suitable in the shallower areas of lakes for evaluating species composition, fish abundance and age structure. They are useful in lentic areas of rivers or transitional waters cat. 3 to 5 as well as in backwaters. 6.2.7.4 Trap net Principle: Trap nets are enlarged fyke nets with wings and a net lead. Water types and categories: Trap nets are often used in the littoral habitats of lakes. They are seldom used in littoral and lentic habitats of rivers and transitional waters or in backwaters. Target species: All species living in the area can be captured.

EN 14962:2006 (E) 14 Suitability: Trap nets are highly suitable in the littoral habitats of lakes for evaluating the species composition, fish abundance and age structure. They may als

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