冰島的鱈魚水產(chǎn)業(yè)在全球擁有最大的規(guī)模,，每年可向市場(chǎng)提供大約20萬噸鱈魚,。與西大西洋崩潰的水產(chǎn)業(yè)相比，這里的漁業(yè)儲(chǔ)備要好得多,。然而盡管如此,，對(duì)鱈魚進(jìn)行的遺傳學(xué)分析顯示，捕魚正在改變著鱈魚的種群，進(jìn)而可能在局部導(dǎo)致崩潰,。
盡管在海面下的不同深度都可以捕獲到冰島鱈魚,，但大多數(shù)的漁船都會(huì)在不足100米深的沿海水域用漁線和漁網(wǎng)進(jìn)行捕撈。而水底拖網(wǎng)能夠?qū)⒉遏~的范圍下降至水下200米左右,。
幾年前,，通過將數(shù)據(jù)記錄器附著在鱈魚身上，研究人員發(fā)現(xiàn),，鱈魚具有截然不同的棲息地：一些鱈魚只生活在淺水中,，而其他鱈魚的活動(dòng)范圍則遠(yuǎn)離海岸——它們只有在春天的繁殖季節(jié)才會(huì)游到岸邊。對(duì)這兩種鱈魚進(jìn)行的遺傳學(xué)分析反映了這種差異：它們分別攜帶了一種不同版本的名為pantophysin I——其功能至今尚未搞清——的基因,。
雷克雅未克市冰島大學(xué)的遺傳學(xué)家Einar Arnason于是尋思,，漁業(yè)捕撈是否會(huì)改變鱈魚儲(chǔ)備的遺傳構(gòu)成。他和同事對(duì)8000多條鱈魚的基因型進(jìn)行了分析,，旨在找出1994年至2003年之間,，不同版本的基因或等位基因的頻率分布在兩個(gè)種群中是如何變化的。他們最終發(fā)現(xiàn),，隨著時(shí)間的流逝,，淺水鱈魚的基因型正在變得越來越少。研究人員在上周的《科學(xué)公共圖書館—綜合》上報(bào)告了這一研究成果,。新的發(fā)現(xiàn)具有重要意義,，這是因?yàn)轺L魚的捕撈在淺水中更為密集。
Arnason預(yù)測(cè),，如果依然保持這樣的捕撈密度,，那么不出10年，“淺水鱈魚將消失殆盡”,。并且如果深水鱈魚不向淺水遷徙——Arnason認(rèn)為這種可能性極大,，因?yàn)樗鼈兊倪z傳差異決定了這種鱈魚更適合在深水活動(dòng)——則整個(gè)鱈魚種群的數(shù)量將大幅減少。此外,，水產(chǎn)業(yè)必須向花費(fèi)巨大的深水捕撈轉(zhuǎn)移,。Arnason和他的同事指出，為了避免鱈魚種群出現(xiàn)崩潰,，必須進(jìn)行必要的禁漁,。
美國紐約州Stony Brook大學(xué)的David Conover表示，重要的問題是,，深水鱈魚是否會(huì)進(jìn)化出淺水鱈魚的習(xí)性,。（生物谷Bioon.com）
生物谷推薦原始出處：
PLoS ONE 4(5): e5529. doi:10.1371/journal.pone.0005529
Intense Habitat-Specific Fisheries-Induced Selection at the Molecular Pan I Locus Predicts Imminent Collapse of a Major Cod Fishery
Einar árnason1*, Ubaldo Benitez Hernandez2, Kristján Kristinsson3
1 Institute of Biology, University of Iceland, Reykjavík, Iceland, 2 Institute of Biology, University of Iceland, Reykjavík, Iceland, 3 Marine Research Institute, Reykjavík, Iceland
Predation is a powerful agent in the ecology and evolution of predator and prey. Prey may select multiple habitats whereby different genotypes prefer different habitats. If the predator is also habitat-specific the prey may evolve different habitat occupancy. Drastic changes can occur in the relation of the predator to the evolved prey. Fisheries exert powerful predation and can be a potent evolutionary force. Fisheries-induced selection can lead to phenotypic changes that influence the collapse and recovery of the fishery. However, heritability of the phenotypic traits involved and selection intensities are low suggesting that fisheries-induced evolution occurs at moderate rates at decadal time scales. The Pantophysin I (Pan I) locus in Atlantic cod (Gadus morhua), representing an ancient balanced polymorphism predating the split of cod and its sister species, is under an unusual mix of balancing and directional selection including current selective sweeps. Here we show that Pan I alleles are highly correlated with depth with a gradient of 0.44% allele frequency change per meter. AA fish are shallow-water and BB deep-water adapted in accordance with behavioral studies using data storage tags showing habitat selection by Pan I genotype. AB fish are somewhat intermediate although closer to AA. Furthermore, using a sampling design covering space and time we detect intense habitat-specific fisheries-induced selection against the shallow-water adapted fish with an average 8% allele frequency change per year within year class. Genotypic fitness estimates (0.08, 0.27, 1.00 of AA, AB, and BB respectively) predict rapid disappearance of shallow-water adapted fish. Ecological and evolutionary time scales, therefore, are congruent. We hypothesize a potential collapse of the fishery. We find that probabilistic maturation reaction norms for Atlantic cod at Iceland show declining length and age at maturing comparable to changes that preceded the collapse of northern cod at Newfoundland, further supporting the hypothesis. We speculate that immediate establishment of large no-take reserves may help avert collapse.
