In an area of Qingdao, a rare swarm of crabs has recently appeared. According to local fishermen, the situation has been existing since last year, and the number is increasing. Crabs can be seen gathering on the beach reef almost every day. These crabs are not only abundant, but also large in size, some even weighing tens of catties.

It is understood that these crabs were artificially introduced for some reason, and their arrival has brought no small challenges to the local fishery. Because crabs have strict requirements on water quality, food, etc., if the breeding environment is not appropriate, it is easy to lead to the death of the crab population or disease.

In response to this situation, the local government has taken a series of measures, including strengthening supervision, banning illegal fishing, and conducting research on artificial crab farming to improve its survival rate and reproductive capacity. In addition, fishermen are also encouraged to adopt sustainable farming methods, such as the use of ecological crab farming techniques, to reduce the impact on the environment.

However, although the government has taken various measures, it is still unable to fully control the number of crabs. In this regard, some experts said that this may be due to factors such as the marine ecosystem itself having certain regulatory functions and the strong adaptability of crabs themselves. In the future, further research on marine biodiversity needs to be further strengthened in order to better protect and manage marine resources.

Based on the above, please answer the following questions:

1. Why has a crab cluster appeared in a sea area of Qingdao recently?

2. Will these crabs have any impact on local fisheries?