fish, threespined, three spined, three-spined, threespine, three spine, three-spine, stickleback, sticklebacks, anadromous, freshwater, marine, salt, water, brackish, pond, estuary, tiddler, tittlebat, sprick, Gasterosteus aculeatus, male, territory, territorial, intruder, chase, chasing, aggressive, aggression, fight, fighting, defend, defending, attack, attacking