Spawning Behavior of Lingcod in the Seattle Aquarium

Abstract

Lingcod (Ophiodon elongates) are members of the family Hexagrammidae and are found in the northeast coastal waters of the Pacific Ocean. Hexagrammids are demersal spawners with the male fish guarding eggs until hatching occurs. The spawning behavior of Lingcod has only been observed and described once in the literature (Wilby 1937). Although other investigators have described various aspects of Lingcod life history and reproductive activity (for example, Jewell 1968; Low and Beamish 1978; LaRiviere and others 1981; Giorgi 1981; Cass and others 1990; Jagielo 1994), none directly observed spawning. Withler and others (2004) genetically evaluated progeny and documented polygamous mating by Lingcod. This note describes a Lingcod spawning event in the Seattle Aquarium and compare this spawning to that described previously by Wilby (1937). The Underwater Dome exhibit of the Seattle Aquarium is in the form of an igloo-like public observation volume immersed in a large cylindrical vessel. The vessel is approximately 20 m in diameter and 6 m deep, containing more than 1800 m of filtered seawater pumped from adjacent Elliot Bay, in an open system with the water discharged back to the bay. The surface of the vessel is not enclosed, and is protected by an awning covering a portion of the water surface. Environmental conditions inside the exhibit, such as temperature and lighting, match ambient conditions. A low-light level is maintained in the exhibit at night. The exhibit topography mimics rocky and nearshore habitat conditions found in the Salish Sea. The highrelief rocky reef structure is made of concrete, and the bottom is covered with a shallow layer of coarse beach sand. The exhibit is home to a variety of fish and invertebrate species found in local waters. The animals are fed a variety of fish and shellfish similar to their natural diet. The Lingcod feed primarily on forage fish and squid, and occasionally prey on smaller exhibit fish, usually salmonids. Lingcod in the exhibit typically spawn each season between mid-December and mid-March, usually near year-end, using one or more of 3 specific locations. Characteristics of the 3 sites are consistent with sites selected by fish in the wild (KWJ, pers. obs.), distinguished by rocky reef ledges with deep cracks or crevices suitable for deposition of egg masses, supporting the premise that physical characteristics of the exhibit are conducive for display specimens to behave and reproduce in near-natural conditions. The site of the observed spawning is an approximately parallel-sided cavity 20 cm wide between a flat-sided boulder and a vertical reef surface. The site is about 2 m from viewing windows. The dome exhibit was home to 5 adult Lingcod ranging from 75to 110-cm total length at the time of the observed spawning. Two of the fish were known to be female and 2 were known to be male. The sex of the 5th fish was unknown. The ages of the fish were also not known. Observations were visual and notes were made after the event. Measurements were made using a 1-m-long plastic tube graduated in 10-cm increments. On 1 January 2015, a pair of Lingcod spawned in the Underwater Dome exhibit of the Seattle Aquarium. The spawners were the largest female and largest male in the exhibit. The female was gravid and swollen to the point of concern by aquarium staff that she was egg-bound. The site selected by the spawners was the site most frequently used for egg laying in previous years. The male fish had established long-standing dominance of this site during the spawning season by remaining at the location, performing courtship display when females were present, and chasing other fish from the area. At approximately 08:30 Pacific Standard Time, in crepuscular conditions, the female Lingcod was observed by a maintenance diver at the spawning location. She was aligned with the cavity with her ventral side up. The fish was alternately squirming and quivering. The male was nearby (Fig. 1A). After an GENERAL NOTES