垂釣對新北市雙溪河魚類組成的影響

Abstract

封溪護魚保育措施，近年來在北臺灣溪流管理上蔚為風潮，且多數實施封溪護魚河段之溪流資源均有回復之趨勢，但所保育之資源成果卻面臨如何公平合理之資源永續利用。因此，探討如何建立有效的封溪護漁河段之經營管理模式，進而落實資源的永續利用也就格外重要。 本研究區域選定新北市雙溪河流域，雙溪河因具有天然且良好之溪釣環境，加上所執行封溪護魚措施頗有成效，且自2006年起開始實施特定時間內部份河段開放垂釣，但無配套管理機制，包括漁獲限制與每日每人垂釣時間的限制。 本研究自2012年1月至12月，假設開放垂釣河段之魚類資源，在垂釣開放期間之變化會反映於次要支流下，因此藉由電氣採集法所收集資料用以分析河段別與季節之魚種組成以及魚種別之體長分佈的變化；另外也易垂釣法進行河段別與季節別之魚種組成，進而探討比較開放前、中、後期垂釣行為的影響。 研究結果發現，由魚類組成之變化，垂釣法所釣獲魚隻數量與體長隨著不同保育階段逐漸遞減，電氣採集法具有同樣趨勢，但開放垂釣後的回復期調查中，垂釣性目標魚種的數量已有回復趨勢，由體長頻度資料亦發現有新生魚苗的再加入，顯現以現有垂釣開放兩個月後再行封溪之保育策略對於河段內資源並無太大衝擊，也顯示封溪護魚政策於雙溪河流域確有成效且應持續進行。 將垂釣性目標魚種之平均體長與過去文獻中相關生殖生物學的結果進行探討，本研究中無論以電氣採集法或是垂釣法所採獲之垂釣性目標魚種，平均體長除臺灣鏟頷魚外，均低於成熟體長區間，顯現本流域之垂釣性目標魚種可能面臨某種壓力，造成體長區間略低於成熟體長，若不注意恐會有過漁之可能。 因此本研究結論為，開放垂釣，於開放期間魚類數量減少與較大體型之移除有關，但若無其他干擾因子衝擊，魚類數量約兩個月時間能有回復之情形，因此現有封溪護漁應持續進行，而現有資源，垂釣目標魚種之平均體長均小於個別魚種之成熟體長，且現階段管理並未針對垂釣體型進行限制，因此建議開放垂釣時間仍維持兩個月期間，但由現行每年度開放更改隔1年開放一次，使現有魚類群聚與成長能夠更加穩定。後續也應了解各魚種生物學特性與生活史，尤其針對群聚內之競爭、補食與資源分享等生物間作用，方能整體完善了解溪流魚類群聚是否穩定，與使其穩定之機制。

Stream closing and fish protection conservation measure has become a trendy stream management in the Taiwan. Most segments implementing stream closing and fish protection show positive trend in restoring stream resources, but the fruitful conservation outcome are facing a question whether the benefiting resources are equitably and reasonably used for sustainability; therefore, to establish an effective management model of stream closing and fish protection in river segment in order to implement rules for the sustainable use of resources has become a particularly important issue. This study selected Shuangxi River, New Taipei City as the study site, The experiment for this study took place from January to December,2012, hypothesizing the changing of river segment opening for angling will reflected in the minor tributaries, and therefore, by conducting electro-fishing method to collect data for analyzing the species composition and the changes of the numbers of species and population size between different seasons and segments to discuss about the angling behavior’s impact to the composition of fish; angling method is also practically used in fishing permitted segments of the river in early, mid and late stages of the angling permitting duration to discussed the number of species collected in different stages. The results found that changes in the composition of the fish species, body length of the fishes captured by angling, gradually decreases by different conservation stages, while electro-fishing method has shared the same trend, but for the survey during the restoration stage, the populations of the targeting species for angling trend to restore in numbers, and from the length frequency data also discover that newborn fry has been add into the population, which reveals that the conservation strategy for opening two months a year for angling did not cause significant impact on the population size, which suggest that the stream closing and fish protection policy in Shuangxi River is effective and should be continued. The average body length of angling target species in this study compared with the results of historical data related to reproductive biology by literature reviewing, regardless of the angling target species collected by electro-fishing method or angling, the average body length of both methods are lower than the range of mature individuals, except Onychostoma barbatulus. This reveals that the angling target species of this basin might face certain unknown factors, causing the body length slightly lower than the mature body length, which might contain a possibility of overfishing without monitoring. This study concludes that the decease of population size and removing of the larger body size individual, are related to the angling opening period, but without the disturbance impact cause of the other factors, the restoration of population size could affect in two months, hence the existing stream closing and fish protection regulations should be continued. As to current management has no restriction on capture size, this study recommended by changing the current situation for opening two months a year into opening two months every 2 years, in order the let the fish community maintain a stable effective population size. Further researches on the biological characteristics of each species and life history is recommended, especially for the competition, food, resource and biological effects in order to improve the understanding of the fish community stability and the mechanism to stabilize the population structure.