untitled BRITISH STANDARD BS EN 14962 2006 BS 6068 5 40 2006 Water quality — Guidance on the scope and selection of fish sampling methods The European Standard EN 14962 2006 has the status of a Britis[.]
BRITISH STANDARD Water quality — Guidance on the scope and selection of fish sampling methods The European Standard EN 14962:2006 has the status of a British Standard ICS 13.060.70 12&23 100 >2 EN 14962:2006 (E) Table — Categories for lakes Category Presence or absence of a pelagic or profundal zone Area km Lake category With or without a pelagic or profundal zone < 0,5 Lake category Without a pelagic or profundal zone > 0,5 Lake category With a pelagic and profundal zone > 0,5 Table — Categories for transitional waters Category Width max Depth m m Transitional water category 2 Transitional water category > 100 >2 Within a river or transitional water, categories according to the Tables and 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 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 to 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 6.2.1 Fish sampling by capture 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) 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 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 6.2.2.1 Electrofishing 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 < 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 and 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 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 m and at the relatively shallow sides near the banks and shorelines of deeper rivers, lakes and transitional waters with γ < mS/cm With adjusted electrofishing equipment the depth range may be extended up to a water depth of 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) 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 6.2.6.1 Anchor nets 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 to 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 to 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 12 EN 14962:2006 (E) Water types and categories: This type of anchor net can be used in larger rivers or in transitional waters cat to 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 to 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 6.2.7.1 Traps 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 to 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 13 EN 14962:2006 (E) Suitability: Trap nets are highly suitable in the littoral habitats of lakes for evaluating the species composition, fish abundance and age structure They may also be used in the littoral zone and backwaters of rivers and transitional waters 6.2.7.5 Instream trap Principle: Instream traps are specially constructed and adjusted traps which are installed in fish ways or ladders Fish enter the trap by moving upstream or downstream Water types and categories: Instream traps can be used in fish ways or ladders which are installed in rivers or transitional waters Target species: All migrating and moving species occurring in the area can be captured Suitability: Instream traps are highly suitable for species composition and abundance of migrating or moving fish They may also be useful for evaluating the age structure 6.2.8 Sampling in power plants Principle: At power plants and other water inlets fish are sucked in by the current Often fish are separated from the water before entering the system and are collected Water types and categories: Power plants are mostly operated at larger rivers or transitional waters cat to Water extractions for other purposes are found in most water types and categories Target species: All species occurring in the area may be sampled Depending on the construction situation smaller fish may be sucked in more often than bigger ones Suitability: Under a good constructive situation of the water inlet this method is highly suitable for determining species composition and the estimating fish abundance The method may also be useful evaluating the age structure 6.2.9 Longline Principle: A longline consists of a main line with baited hooks set on short sidelines Water types and categories: Longlines can be used on the bottom in lakes, rivers (cat to 5) and transitional waters (cat to 5) Target species: Species which not regularly occur in catches made by other methods can be captured with longlines Suitability: Longlines may be useful to obtain additional information on species composition 6.2.10 Hook and line Principle: One, seldom more baited hooks are connected to a line and are used as a float-, ground-, spin- or fly-fishing gear by anglers or sports fishermen Water types and categories: Anglers can fish in all water types and categories Target species: Many species living in those waters can be the target species Suitability: The suitability depends widely on the reliability and exactness of the fisherman’s records Results of fishing with hook and line are useful as additional information on the species composition If the catch data of several anglers are documented in binding and qualified statistics, these statistics may be suitable for 14 EN 14962:2006 (E) species composition In order to estimate fish abundance, information on fishing effort has to be included The age structure shall be determined by additional sampling 6.3 6.3.1 Data sampling without capture Principle Data on fish populations may also be sampled without capture 6.3.2 Hydroacoustics (Echo sounding) Principle: Hydroacoustics (or echo sounding) is used to gather information remotely by transmitting a pulsed beam of sound energy into a water body and by subsequently detecting and analysing the return echo Systems are available with single-, dual-, and split-beams, although the latter type has recently superseded the other two systems The technique is mostly used with the acoustic beam orientated in the vertical axis, although a recent development also allows beam orientation in the horizontal axis Systems are usually deployed from a moving boat in lakes or rivers, while a fixed installation may also be used in rivers A computer is required for control of the echo sounder in the field and for data processing Water types and categories: With the acoustic beam orientated in the vertical axis the technique allows the sampling of relatively deep lakes and rivers, with a horizontal beam inshore and surface areas of shallower lakes, rivers and transitional waters Target species: The technique is presently unable to identify species, although this can be attained by the simultaneous use of an appropriate capture technique such as gill netting, seining or trawling Suitability: Hydroacoustics is highly suitable for estimating abundance The age structure can only be determined to a relatively low degree of precision and accuracy As species cannot be identified other catching methods shall be used in combination 6.3.3 Video recording Principle: Fish are forced to swim through a specifically lighted area of a fish migration device (e.g fish ways, fish-lift), to be identified and counted in a continuous way, either directly or by video recording Fish can be observed as a silhouette by a “top-down vision” when passing through a bright bottom area or by a lateral observation when passing in front of a vertical window The latter one is generally preferred since the majority of species is identifiable from lateral-viewed morphological criteria Water types and categories: Video recording can be used in fish ways or ladders which are installed in rivers and transitional waters and where the water transparency is high enough Target species: All migrating and moving species occurring in the area can be observed and counted Suitability: Video recording is highly suitable for species composition and abundance of migrating or moving fish The efficiency of the method depends on species, fish length, light and water transparency 6.3.4 Fish counter Principle: Electrodes are installed in a fish pass or ladder and passing fish generate an electronic signal which is recorded Water types and categories: In rivers and transitional waters fish counters can be installed Target species: Fish counters principally detect only individual fish Suitability: Fish counters are highly suitable for estimating the total number of migrating fish For species identification it shall be combined with instream traps 15 EN 14962:2006 (E) 6.3.5 Underwater observations 6.3.5.1 General Fish are identified and counted by snorkelling or scuba diving in waters with high transparency 6.3.5.2 Snorkelling Principle: By snorkelling in rivers or lakes fish can be identified and counted Water types and categories: Snorkelling is possible in shallow areas of lakes and small rivers (cat to 3) Target species: All species occurring in the habitat can be detected Suitability: Snorkelling may be useful for the determination of species composition and age structure and the estimation of fish abundance 6.3.5.3 Scuba diving Principle: By scuba diving in rivers or lakes fish can be identified and counted Water types and categories: Scuba diving is possible in shallow areas of lakes and smaller rivers (cat to 3) Target species: All fish species occurring in the habitat can be detected Suitability: Scuba diving may be useful for the determination of species composition and age structure and the estimation of fish abundance 6.4 Tabulated synopsis of sampling methods In Tables to a synopsis of the different sampling methods is given Each method is classified according to its suitability for the determining species composition (C), age structure (S) and estimating abundance (A) Classification levels are high (H), medium (M) and low suitability (L) Table covers the sampling methods which are suitable for rivers, Table those suitable for lakes and Table those for transitional waters The sampling methods are described in more detail in 6.2 and 6.3 Water and/or species specific conditions may require the suitability level of certain methods to be modified Such modification shall be accompanied by a qualified explanation Table — Sampling methods in different habitats of river categories River cat River River cat cat Littoral Middle (Brook) habitat Electrofishing (6.2.2) Electrofishing by C wading (6.2.2.2) A S Electrofishing C from a boata A (6.2.2.3) S 16 H H H H H H H H H H H H H H H M M L River cat River cat Littoral Middle, Middle, Littoral Middle, Middle, habitat bottom mid-water habitat bottom mid-water H H H H H H H H H H H H EN 14962:2006 (E) Table (continued) River cat River cat River River cat cat Littoral (Brook) habitat Seines (6.2.3) Beach seine (6.2.3.2) Normal seine (6.2.3.3) Pelagic seine (6.2.3.4) C A S C A S C A S Trawls and push net (6.2.4) Bottom trawl C (6.2.4.2) A S Pelagic trawl C (6.2.4.3) A S Push net C (6.2.4.4) A S Gill nets and trammel net (6.2.5) Bottom gill netb C (6.2.5.2) A S Pelagic gill net C (6.2.5.3) A S b Vertical gill net C (6.2.5.4) A S Drift net (6.2.5.5) C A S b Trammel net C (6.2.5.6) A S Anchor nets (6.2.6) Anchor net from C a bank (6.2.6.2) A S Anchor net from C a vessel (6.2.6.3) A S Traps (6.2.7) b Basket (6.2.7.2) C A S Middle M M M River cat Littoral Middle, Middle, Littoral Middle, Middle, habitat bottom mid-water habitat bottom mid-water M M M M M M M H L L M L M H L L L L H H H H H H L L L L L L L L L L L L M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M L L M L L M M L M L L M M L H H H H H H L L L L L L L L L H H H H H H H H H L L L H H H L L L 17 EN 14962:2006 (E) b Fyke net (6.2.7.3) Table (continued) River River River cat River cat River cat cat cat Littoral Middle Littoral Middle, Middle, Littoral Middle, Middle, (Brook) habitat habitat bottom mid-water habitat bottom mid-water M M M M M M L L L M M M M L L H H H H H H H H H H M M M M M H H H H H H M M M L L L C A S b Trap net C (6.2.7.4) A S Instream trap C (6.2.7.5) A S Sampling in C power plants A (6.2.8) S Longline (6.2.9) C A S L L Hook and linec C (6.2.10) L L A S Hydroacoustics C (6.3.2) A S Video recording C H H (6.3.3) A H H S M M Fish counter C (6.3.4) (6.2.7.5) A H H See NOTE S Underwater observations (6.3.5) Snorkelling C M M (6.3.5.2) A M M S M M Scuba diving C M (6.3.5.3) A M S M where C is (species) composition; A is (fish) abundance; S is (age) structure; H is method of high suitability; M is medium suitability; L is low suitability L L L L H L L L H L H L H H M H H M H H M H H H M M M M M M NOTE 'C' in combination with a number, is used when a method shall be combined with another method See also for selecting sampling methods a Only in areas up to a max water depth of m b Only in areas with low current or in backwaters c The suitability level may be changed to 'M' if a binding and qualified fishery statistics is used 18