Which Built by has a Name of northern jaeger?
CREATE TABLE "american_seafoods_company_fleet" (
  "name" text,
  "length" text,
  "tonnage" real,
  "built_by" text,
  "year" real,
  "engines" text,
  "horsepowers" real,
  "former_names" text
);
SELECT "built_by" FROM "american_seafoods_company_fleet" WHERE "name"='northern jaeger';