Grunion until the next tide series high enough reaches them 10 or more days later. Grunion eggs can extend incubation and delay hatching if tides do not reach them for an additional four weeks after this initial hatching time. Most of the eggs will hatch in 10 days if provided with seawater and the agitation of the rising surf. The mechanical action of the waves is the environmental trigger for hatching. The rapidity of hatching, which occurs in less than one minute, indicates it is probably not an enzymatic function of a softening of the chorion as in some other fishes.
USS Grunion she patrolled north of Kiska Island, stated she had been attacked by a Japanese destroyer and had fired torpedoes at her with inconclusive results. She operated off Kiska throughout July and sank two enemy patrol boats as she waited for enemy shipping. On 30 July, the submarine reported intensive antisubmarine activity and was ordered back to Dutch Harbor. The "Grunion" was never heard from again. Air searches off Kiska were fruitless, and on 5 October the "Grunion" was reported overdue from patrol and assumed lost with all hands. Her name was stricken from the Naval Vessel Register on 2 November