Governor Deval Patrick is asking the US commerce secretary to raise fishing catch limits by the end of next week. Patrick made his request in a letter yesterday to Gary Locke as a follow-up to Locke’s visit to Massachusetts last month. Patrick said fishermen are facing severe hardship because of unnecessarily low catch allotments, and he asked Locke to raise the limits by Oct. 15. The limits are intended to protect fish stocks, but fishermen say that more can be caught without hurting efforts to stop overfishing. Patrick also suggested that Locke use $2.1 million in fines collected from fishermen to pay for an assessment of the health of groundfish stocks.