Complex sentence: The primary mission of the Northeast Fisheries Science Center is the management of fisheries on the Northeast shelf, however it also oversees the operation of the National Systematics Lab, in conjunction with the Smithsonian Institution.
Split into simpler sentences: The primary mission of the Northeast Fisheries Science Center is the management of fisheries on the Northeast shelf. However, it also oversees the operation of the National Systematics Lab, in conjunction with the Smithsonian Institution.