Atlantic cod, Gadus morhua, was a heavily overfishing species in Northern Atlantic fisheries to the point where any commercial fishing of the species became unsustainable. Atlantic cod is on the International Union for Conservation of Nature’s Red List Threatened Species. It was thought that overfishing caused early maturation in smaller sized fish due to the high selection of larger cod, which kept the populations from reaching their growth potential. If it was believed that cod were not reaching growth potential because due to fishing pressures populations genetics began favoring the smaller sized individuals that reached maturity early and populations would not reach original sizes. This study compared experimental and wild results of Atlantic cod using a genomic-wide analysis of 346,290 loci observing single-nucleotide polymorphisms (SNP). The genome of Atlantic cod was sequenced from archives of Atlantic cod before intense fishing pressures and after extreme decline in populations from overfishing using scales and otoliths. These archives revealed the genomic variation of many generations that were kept for fisheries management. The results revealed a large difference between experimental genomes and wild genomes. The genomic range of wild Atlantic cod was found to be not genetically limited in their environment due to overfishing; whereas, the selectivity of cod generations in a controlled experimental environment produced more significant genetic variation across generations. However, in the wild, polygenic evolution can still occur in the genetic diversity of wild populations due to long term environmental conditions and not fishing pressures. Other marine species can be directly influenced by fishing pressures and genetic loss can occur in Atlantic cod based on experimental results, but the conditions for this to occur is still under research. Due to these results from this study, it supports that Atlantic cod populations will reestablish from significant decreases in fishing pressures because of no genomic variation loss. A reason that the wild population results differ from the experimental results is because wild Atlantic cod populations respond to pressures from phenotypic plasticity and this is supported by density-dependent growth. Wild populations are much larger than experimental populations because wild populations will hold more genomic variation across more individuals within the population carrying it on to future generations.
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