Spot Pattern Stability During Five Years of Growth of a Captive Giant Sea Bass, Stereolepis gigas

Abstract

Adult Giant Sea Bass (Stereolepis gigas) (GSB) are the largest teleosts inhabiting California’s nearshore habitats. They attain a maximum total length of over 2.7 m, a weight of up to 255 kg, and an age of at least 76 years (Allen 2017; Allen and Andrews 2012; Domeier 2001). All lengths hereafter are total lengths. They range from Humboldt Bay, California to Oaxaca, Mexico, including the entire Gulf of California (Cornish 2004; Domeier 2001); 73% of the species’ range occurs in Mexico (Ramirez-Valdez et al. 2021). Giant Sea Bass spend just under a month as floating eggs and planktonic larvae before settling to the bottom (Benseman and Allen 2018). After planktonic settlement, the youngof-the-year (YOY) of GSB of between 10 and 80 mm occupy habitat between 2 and 38 m in depth (Benseman and Allen 2018; Couffer and Benseman 2015; Couffer 2017). The YOY at this size range occupy wide expanses of open sand or sandy-mud away from rocks, jetties, piers, debris, and other hard structures (Benseman and Allen 2018; Benseman et al. 2019; Couffer and Benseman 2015; Couffer 2017). Benseman and Allen (2018) found that newly-settled YOY were most abundant over soft-bottomed habitat within 300 m of the heads of submarine canyons that begin close to shore. Couffer (2020) described the four centers of abundance for newly-settled YOY located by Benseman and Allen (2018) as GSB nursery sites. The known California nursery sites include Redondo Beach in Los Angeles County, Newport Pier and Big Corona del Mar State Beach in Orange County, and La Jolla Shores in San Diego County. No significant submarine canyons that closely approach sandy shorelines exist along the Pacific coast side of the Baja California Peninsula; however, potential nursery site habitat exists off the tip of the peninsula and within the Gulf of California. The topic of nursery sites within the Mexican portion of the species’ range remains unexplored (Couffer 2020). The smallest verified YOY found in a nursery site was 10 mm. However, on 11 June 2021, a school of nine fish smaller than 10 mm that appeared to have very similar body shape and behavior to newly-settled YOY was filmed by a diver in the La Jolla Shores nursery site; unfortunately, the image resolution was not high enough to conclusively identify the fish as GSB. Between 10 mm and 20 mm, YOY are black with several small white patches around the face and sides (Benseman and Allen 2018; Couffer and Benseman 2015). The white patches are too variable for long-term re-identification of individuals. Black-phase YOY have large black spiny dorsal and pelvic fins and translucent soft dorsal, pectoral, anal, and caudal fins. During the black phase, black spots do not exist on the sides. When stressed, the black background often lightens considerably but no black spots appear (Couffer 2017). From approximately 20 mm to 40 mm, their background pigmentation lightens from black through a brown phase into orange. Spiny dorsal fin pigmentation mirrors the background pigmentation seen on the sides. The large pelvic fins remain black. The black background morphs to a dark brown and as the brown lightens, faint black spots begin to appear. As the brown continues to lighten, the black spots