International Journal of Marine Science, 2025, Vol.15, No.2, 92-106 http://www.aquapublisher.com/index.php/ijms 98 different regions. Some studies have found through sequence analysis of mitochondrial control zones that the wild population of pimples in different Southeast Asian countries is mixed in the same haplotype network, and there is no obvious regional clustering. This implies that historically they may have been connected by sea currents, or that in modern times, they were caused by the transport of parent shrimp in the area. The second is to spread to Africa. At the end of the last century, some aquatic companies were optimistic about the vast land and good water quality along the coast of Africa, and tried to breed Giant tiger prawns there. Madagascar introduced pimples from Asia in the late 1980s and established a breeding farm. It is still the only country in Africa to achieve a large-scale pimples export (the population of pimples that escape and reproduce in its wild waters have also been found). In addition, Mozambique, Tanzania and other places have also recorded sporadic introduction records, but due to technology and capital, no major industries have been formed. The spread of varnish shrimp in Africa is generally not as successful as that of varnish shrimp, which is related to the characteristics of varnish shrimp with higher environmental requirements, susceptibility to diseases, and longer growth cycles (Simtoe et al., 2025). 5 The Impact of Human Activities on Population Structure and Geographical Pattern 5.1 Genetic mixing and germplasm erosion driven by aquaculture Large-scale aquaculture activities have had a profound impact on the genetic structure of shrimp populations. Artificial breeding often breaks down natural geographical barriers, mixing originally geographically isolated populations, resulting in intensifying genetic communication. In breeding practice, shrimp seedlings in different regions tend to circulate across regions. Most of the Pacific white shrimp strains cultivated in Asian countries originate from similar parental germplasms, which led to the "fusion" of the originally evolved Eastern Pacific lineage and the Asian native shrimp gene pool. Molecular testing found that some Asian Pacific white shrimp populations contain genetic components of multiple geographical origins, and their heterozygation is maintained at a moderate level, but the differences between populations are reduced. This shows that aquaculture activities have contributed to the mixed unity of germplasms from different sources (Wu et al., 2025). Secondly, aquaculture may cause germplasm erosion due to artificial selection and other reasons, namely, the decline in genetic diversity and the degradation of specific traits. High-intensity breeding and in-mating have reduced the effective population size of many breeding shrimp populations and lost allele. Domestic studies have shown that after continuous multigenerational breeding, the average heterozygous degree and allelic number of Pacific white shrimp farming population have significantly decreased compared with the wild population. Especially in the absence of a good breeding plan, breeders often repeatedly use a few parent shrimps to reproduce, resulting in a narrowing of the genetic background of offspring. The selection pressure of artificial environments is different from that of natural environments and may also lead to the differentiation of breeding populations from wild populations in terms of traits. Farming conditions are usually sufficient resources and have low predation pressure, so they may tend to retain genotypes that sacrifice stress resistance at the expense of high growth rates. Comparative studies found that the breeding of Pacific white shrimp population showed significant changes in allelic frequency on some genes related to immunity and metabolism, reflecting the role of artificial selection. 5.2 Ecological risks of escape populations and non-local spread 5.2.1 Examples of establishing wild populations in non-native places Large-scale shrimp farming is accompanied by frequent escape events, and some alien species can survive and reproduce in wild environments in non-original places, forming new populations, posing a potential threat to the local ecology. A typical case is the "secondary wildization" of Whiteleg shrimp in Asia. Although Vannebane shrimps are native to the Americas, they have repeatedly escaped into the estuary and near the sea due to typhoons and dam damage. Wild breeding Pacific white shrimp populations have been monitored in China's Pearl River Estuary and the coast of Taiwan. They lay eggs and grow in warm seasons, and some individuals can even survive overwinter, indicating that the species has been successfully colonized in some new areas (Chavanich et al., 2016). Another case is the spread of prawns in Africa. The Giant tiger prawns at Madagascar farms once escaped to nearby bays. Local fishermen are now able to catch commercially valuable Giant tiger prawns, indicating that the species has established wild populations along Madagascar's coast. Even along the Brazilian coast of South America, records of invasion of prawns have been found: giant tiger shrimps have been continuously captured in
RkJQdWJsaXNoZXIy MjQ4ODYzNA==