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 the Pacific on 24 May. A week later, as she transited the Caribbean Sea for Panama, she rescued 16 survivors of the USAT "Jack", which had been torpedoed by the , and conducted a fruitless search for 13 other survivors presumed to be in the vicinity. Arriving at Coco Solo on 3 June, the "Grunion" landed the survivors and continued on to Pearl Harbor, arriving on 20 June. Departing Hawaii on 30 June after ten days of intensive training, the "Grunion" touched Midway Island before heading toward the Aleutian Islands for her first war patrol. Her first report, made as