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To enable pupils to understand how salmon spawning occurs, make them aware of the factors that affect egg and fry survival and the importance of habitat conservation. Presentation: Lesson 3 Teachers Guidelines This lesson could begin by telling the story of “An Bradán Feasa” to the pupils to stimulate interest. Salmon begin life as spawn or eggs. A female salmon returns to her natal river or river of birth to spawn. Salmon, sea trout and brown trout often use spate rivers for spawning. A fast flowing, hilly or mountain river subject to floods or high water is described as a spate river. The flood level rises quickly after heavy rain but drops just as fast. While water levels in a spate river may fluctuate very quickly, it may, at the same time, have some deep holding pools with good gravely areas for salmon to spawn. A salmon travels upstream to the source of a river where the water is shallow and fast flowing and where the riverbed is strewn with clean, loose gravel. After selecting an area in the stream, she excavates a hole in the gravel with her tail and nose, sometimes helped by the male. The gravel is piled high, often reaching the surface of the water, and always downstream of the excavation. Then the female deposits her ova (up to 5,000 eggs) in the deepest part of the excavation. The male, who is alongside throughout, fertilises the eggs as they are deposited from the female. When spawning is complete, the hen buries the ova (fertilised eggs). Then all of the excavation is fully covered, forming a mound of approximately 40cm by 40cm, depending on the size of the fish. The mound of gravel or egg nest made by a trout or salmon in a stream is called a “redd”. A small number of females and males (about 5%) may go back to sea a second time and return to spawn again. Salmon that return to sea after spawning are called spent fish or kelts and some even return a third time. This completes the life cycle of a salmon. The presence of clean, loose gravel in a spawning bed is essential to ensure a free flow of oxygen-rich water through the stones for salmon eggs to develop. Field drainage, bog drainage, pollution, overgrazing, afforestation and deforestation can threaten survival of juvenile salmon. All of these can impact negatively on clean, loose gravel. To highlight the importance of good-quality gravel in the spawning area, a simple experiment, oxygen in water, can be carried out. The idea of habitat or home of a plant, animal, insect or fish can be a difficult concept for some pupils to grasp. Discussing the habitats of the pupils, animals, insects or birds in your area could be a good exercise to reinforce this concept. Endangered habitats can be protected by building or erecting fences along the banks of the stream. This allows vegetation to grow and stops silt from falling into the river. Plants provide plenty of leaf litter for the local insects or invertebrates. Putting fewer sheep on mountains means more grass for the animals and less land erosion – the animals are happy and fish can thrive. To illustrate this idea, an experiment on Land Erosion can be carried out Too many coniferous trees planted along the banks of a stream are not good. They block light completely and prevent other vegetation from growing. The banks become bare and muddy. When it rains, silt from the bare muddy banks lodges in the gravel bed. Needles from the trees drop into the stream, producing acid which sours the water. The spawning eggs in the stream will not survive. Pupils could be asked to suggest a solution for this problem, e.g. planting trees correctly near a stream or river environment. Much damage is also caused to streams and small and large rivers by arterial drainage, which is the drainage of a river bed and its adjoining tributaries. To aid with the teaching of this lesson, a glossery of terms and definitions discussed in this lesson are available Revision Two different types of revision material accompany this lesson; activity cards and whiteboard material. The activity card is a 3 page document that is filled out by the pupils to test their knowledge of the lesson taught. The teacher can decide if the activity card is filled out individually or in teams The whiteboard resource tests the pupils knowledge of the lesson taught. Pupils are encouraged to actively engage in answering questions relating to salmon spawning, factors affecting egg and fry survival and habitat conservation. At the end of the lesson, Pupils should know How and where spawning occurs. How landslides occur and the factors that cause stream and riverbank erosion. That the conservation of streams is necessary to ensure that salmon eggs and fry survive. How and where spawning occurs. How landslides occur and the factors that cause stream and riverbank erosion. That the conservation of streams is necessary to ensure that salmon eggs and fry survive.
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Is iasc suimiúil é an bradán ar go leor bealaí. Is féidir leis maireachtáil i bhfionnuisce agus nó san fharraige. Maireann an bradán i ngnáthóga éagsúla i rith a shaoil. Filleann cuid mhaith bradán ar an abhainn inar rugadh iad, chun bás a fháil ann. Sa cheacht seo pléitear áit sceite an bhradáin, an ghnáthóg is oiriúnaí don sceitheadh agus fás an bhradáin ina (baineann) ina gilidín agus ina dhiaidh sin ina muóg. Inis an scéal “An Bradán Feasa” chun spéis na bpáistí a mhuscailt sa bhradán. Tosaíonn saolré an bhradáin leis an ubh. Cá sceitheann an bradán? Filleann an bradán baineann ar an abhainn inar rugadh í chun sceitheadh. Sceitheann an bradán, an breac geal agus an breac donn go minic in abhainn tulca. Tugtar abhainn tulca ar abhainn sléibhe mearshiúlach a mbíonn tuilte ann. Nuair a bhíonn báisteach throm ann ardaíonn leibhéal an uisce go tapaidh san abhainn ach íslíonn an tuile go luath ina dhiaidh sin. Is minic a bhíonn linnte doimhne le fáil in aibhneacha mar seo agus bíonn neart gairbhéil iontu chomh maith. Oireann timpeallacht mar seo do sceitheadh an bhradáin. Déanann an bradán baineann a bealach suas go dtí foinse na habhann. Bíonn gairbhéal glan scaoilte ar ghrinneall na habhann anseo, áit a ritheann an t-uisce go tapaidh. Tochlaíonn an bradán baineann cuas sa ghairbhéal lena heireaball agus lena srón. Amantí cabhraíonn an bradán fireann léi. Beireann an bradán baineann a cuid uibheacha sa chuid is doimhne den chuas. Bíonn suas le cúig mhíle ubh sa “sceith.” Déanann an bradán fireann na huibheacha a thoirchiú de réir mar a bheirtear iad. Clúdaíonn an bradán baineann na huibheacha le carn gairbhéil nuair atá an sceith thart. Carn mór (40cm faoi 40 cm) a bhíonn ann de ghnáth, ag brath ar mhéid an bhradáin. “Clais” a thugtar ar an gcarn gairbhéil sin. Déanann an bradán baineann agus an bradán fireann a mbealach síos an abhainn arís i dtreo na farraige. Ní éiríonn ach le timpeall 5% díobh áfach a mbealach a dhéanamh amach san fharraige arís agus filleadh ar ais chun sceitheadh don dara huair. Tugtar “iasc sceite” ar bhradán a d’fhill ar an bhfarraige tar éis sceitheadh. Éiríonn le cuid bheag acu seo an turas chun na farraige agus ar ais a dhéanamh trí huaire. Is í seo an chéim dheireanach i saolré an bhradáin. Bíonn gá le gairbhéal glan scaoilte sa leaba sceite. Ritheann uisce lán d’ocsaigin tríd an ngairbhéal. Bíonn ocsaigin ag teastáil ó na huibheacha óga chun fás agus forbairt. Cuireann truailliú, coillteoireacht, dífhoraoisiú, feirmeoireacht agus scéimeanna draenála isteach ar ghnáthóg an bhradáin toisc go ndéanann siad dochar don ghairbhéal glan. Is féidir an turgnamh “Ocsaigin san Uisce”a dhéanamh le taispeáint cé chomh tábhachtach is atá gairbhéal glan sa leaba sceite. Is coincheap deacair go leor le tuiscint é gnáthóg. Chabhródh plé ar na gnáthóga áitiúla leis na páistí chun an coincheap seo a thuiscint níos fearr. D’fhéadfá tagairt a dhéanamh do na gnáthóga difriúla sa gharthimpeallacht, ina maireann éin, ainmhithe nó feithidí. Is féidir gnáthóga atá i mbaol a chosaint nó a chaomhnú trí chlaíocha a thógáil ar bhruach na habhann. Tugann na claíocha seo fothain don fhásra agus coscann siad an glár ar thitim isteach san abhainn. Cuireann plandaí bruscar duillí ar fáil ina maireann feithidí agus inveirteabraigh. Dá laghdófaí méid na gcaorach ar na sléibhte bheadh níos mó féir ann dóibh agus bheadh níos lú creimeadh talún i gceist. Bheadh deis níos fearr ansin ag ainmhithe agus ag éisc fás agus forbairt a dhéanamh. Is féidir an turgnamh Creimeadh Talún a dhéanamh ag an bpointe seo. Níor chóir an iomarca crann buaircíneach a chur ag fás ar bhruach na habhann. Dorchaíonn siad na bruacha agus coscann siad fásra eile. Éiríonn na bruacha lom agus lábach. Titeann glár ó na bruacha isteach san abhainn féin nuair a bhíonn báisteach ann. Nimhíonn na snáithidí ó na crainn an t-uisce chomh maith. Cuireann a leithéid seo isteach go mór ar ghnáthóg an bhradáin. Pléigh réitigh éagsúla ar an bhfadhb seo leis na páistí – mar shampla an bealach ceart le crainn a chur cois abhann. Déanann draenáil na n-aibhneacha agus na gcraobhaibhneacha an-dochar do na gnáthóga freisin. www.cfb.ie Nasc leis an bPríomh-Bhord Iascaigh agus na Boird Iascaigh Réigiúnacha.