The Coast Guard ordered a second Soviet fishing vessel into Boston yesterday for violating U.S. fishing laws, and the State Department summoned an official of the Russian embassy to urge Moscow to "ensure that violations cease."

The latest vessel accused of fishing violation is the Antanas Snechkus, a 503-foot transport-refrigerator ship that served as the seagoing headquarters of the Soviet fishing fleet off New England. Coast Guard officials said the Snechkus was carrying 110 tons of prohibited fish, including some caught by the 275-foot trawler Taras Shevchenko, which was seized by the Coast Guard early Sunday.

Coast Guard officials said the detention of the refrigerator ship appeared unprecedented in that the ship is not being declared seized but the allegedly illegal catch is. A recommendation to the Commerce Department to impose fines for illegal fishing is also being considered by the Coast Guard.

At the White House, press secretary Jody Powell maintained that the actions were taken only after the United States demonstrated "the maximum degree of restraint that could be expected." As for the future, Powell suggested that the United States will take a hard line toward violations of the 200-mile limit, but said that each case will be judged individually according to the "severity" of the violation.

At the State Department, Deputy Secretary Warren Christopher called in Vladillen Vasey, the third-ranking official of the Soviet embassy, and warned him that continued violations by Russian vessels could affect relations between the two nations.

Christopher "reiterated the deep concern of the U.S. government over the continued pattern of violations," a State Department statement said.

He "urged that extraordinary measures be taken to ensure that violations cease so that this situation will not contribute to a worsening of our bilateral relations," the statement said.

Powell, who said the series of events showed that "the President is a very patient and reasonable person but that no person's patience is unlimited," gave this version of what led to [TEXT ILLEGIBLE] will be his whether to press the trawler charges, which could seek up to $50,000, jail sentences up to six months or confiscation of the ship.

In Moscow, United press International quoted a spokesman for the minister of fishing as saying Russian has begun an investigaion of the trawler's seizure. UPI noted that the Soviet is engaged in negotiations with Japan to set quotas for Japanese fishing boats inside Russia's own 200-mile limit.

The Taras Shevchnko was seized because it allegedly had exceeded the limit of 2.5 metric tons of river herring by 1.5 tons. Ships are allowed to fish inside the 200-mile limit if they hold their catch to specific amounts of specific fish.

Powell said the ship's logs indicated that on previous occasions it had been well over its legal limit.

He said the great bulk of the fish it has already caught above that limit had been transferred to cargo ships, including the Antanas Snechkus.

Powell said the most strict action the United States could take was seizure of a vessel. Under such a procedure, it orders the ship into a U.S. port where civil or criminal charges, handled by a U.S. attorney, can be filed against a vessel or a captain.

Lesser procedures involve issuance of a "notice of violation," with fines reaching $20,000, or issuance of a citation, under which there is no penalty.

He said that in the incidents preceding the seizure of the Shevchenko notices of violation were issued.

The refrigerator ship allegedly carried 93 metric tons of sea perch and almost two metric tons of cod, species which foreigners are prohibited from catching off New England. The ship also had 16 metric tons in excess of the allowable limit for river herring, the Coast Guard alleged.

The party from the Coast Guard Cutter Reliance boarded the refrigerator ship after the logs of the earlier seized trawler indicated that excess river herring had been transferred to a larger ship for processing and shipment to the Soviet Union.