冰岛的鳕鱼水产业在全球拥有最大的规模，每年可向市场提供大约20万吨鳕鱼。与西大西洋崩溃的水产业相比，这里的渔业储备要好得多。然而尽管如此，对鳕鱼进行的遗传学分析显示，捕鱼正在改变着鳕鱼的种群，进而可能在局部导致崩溃。
尽管在海面下的不同深度都可以捕获到冰岛鳕鱼，但大多数的渔船都会在不足100米深的沿海水域用渔线和渔网进行捕捞。而水底拖网能够将捕鱼的范围下降至水下200米左右。
几年前，通过将数据记录器附着在鳕鱼身上，研究人员发现，鳕鱼具有截然不同的栖息地：一些鳕鱼只生活在浅水中，而其他鳕鱼的活动范围则远离海岸——它们只有在春天的繁殖季节才会游到岸边。对这两种鳕鱼进行的遗传学分析反映了这种差异：它们分别携带了一种不同版本的名为pantophysin I——其功能至今尚未搞清——的基因。
雷克雅未克市冰岛大学的遗传学家Einar Arnason于是寻思，渔业捕捞是否会改变鳕鱼储备的遗传构成。他和同事对8000多条鳕鱼的基因型进行了分析，旨在找出1994年至2003年之间，不同版本的基因或等位基因的频率分布在两个种群中是如何变化的。他们最终发现，随着时间的流逝，浅水鳕鱼的基因型正在变得越来越少。研究人员在上周的《科学公共图书馆—综合》上报告了这一研究成果。新的发现具有重要意义，这是因为鳕鱼的捕捞在浅水中更为密集。
Arnason预测，如果依然保持这样的捕捞密度，那么不出10年，“浅水鳕鱼将消失殆尽”。并且如果深水鳕鱼不向浅水迁徙——Arnason认为这种可能性极大，因为它们的遗传差异决定了这种鳕鱼更适合在深水活动——则整个鳕鱼种群的数量将大幅减少。此外，水产业必须向花费巨大的深水捕捞转移。Arnason和他的同事指出，为了避免鳕鱼种群出现崩溃，必须进行必要的禁渔。
美国纽约州Stony Brook大学的David Conover表示，重要的问题是，深水鳕鱼是否会进化出浅水鳕鱼的习性。（生物谷Bioon.com）
生物谷推荐原始出处：
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.
