Donald A. Thomson (1932–2022), A Remembrance

D ONALD A. THOMSON, Professor Emeritus of the University of Arizona, enjoyed saying he was a marine scientist and ichthyologist in the Sonoran Desert. Those dissonant images invariably opened conversations revealing Don’s passion for marine science and his research program of over 40 years in the Gulf of California (Sea of Cortez). Don produced major contributions to knowledge about the ecology and ichthyofauna of the Gulf. He published more than 37 scientific papers and book chapters, but many who travel to the Gulf know of him primarily from the Tide Calendar of the Northern Gulf of California, which he produced annually from 1967 to 1994 (later produced by CEDO, the Centro Intercultural de Estudios de Desiertos y Océanos), or by his two books on the fishes of Gulf of California. His Reef Fishes of the Sea of Cortez, published in 1979 by John Wiley and Sons with Lloyd Findley and Alex Kerstitch (revised and republished by the University of Texas Press in 2000), remains the definitive reference on rocky-bottom fishes in the Sea of Cortez. It was preceded by the Gulf of California Fishwatcher’s Guide, with Nonie McKibbin (1976, 1978), a modest 79-page paperback with precise line drawings beautifully illustrated by Jenean Thomson, his wife. This first-ever field guide to Gulf fishes was self-published by Golden Puffer Press, sold out of his home, and marketed mostly by word-of-mouth; it nevertheless gained wide popularity and went through several printings. Its 209 species included the fishes most likely to be encountered by fishers and divers on near-shore rocky and sandy bottoms and in the tide pools of the northern Gulf. The Guide was significant in its time because it facilitated research and detailed observation of fishes and encouraged conversation among students, sport divers, and fishermen. Likely tattered, it can still be found in many personal libraries, having earned its place there as a repository of treasured memories. In addition to Don’s two books on Sea of Cortez fishes, his research papers ranged from: faunal biodiversity studies (e.g., Brusca and Thomson, 1977, the first faunal inventory of the Pulmo Reefs); predator–prey studies (e.g., Dungan et al., 1982); environmental impacts (e.g., Thomson et al., 1969; Robinson and Thomson, 1992); fish ecology (e.g., Thomson and Lehner, 1976; Thomson and Gilligan, 1983, 2002; Kotrschal and Thomson, 1986); fish taxonomy (e.g., Thomson and Eger, 1966; Moffat and Thomson, 1975); and behavioral biology of spawning in the Gulf Grunion, Leuresthes sardina (e.g., Reynolds and Thomson, 1974, 1979; Reynolds et al., 1976; Thomson and Muench, 1976). This scholarship grew from research based on extensive field work to investigate and document the ecology and biodiversity of fishes in an area poorly known and sparsely represented in natural history collections. As curator of the University of Arizona Fish Collection, he greatly expanded its holdings during his tenure. In 2021, the collection included more than 12,000 lots representing over 950 species and approximately 175,000 specimens accessioned between 1925 and 1998. However, the majority of the collections (about 75%) were made between 1964 and 1978, a period corresponding with Don’s focused efforts to document the ichthyofauna of the Sea of Cortez. The current curator, Dr. Peter N. Reinthal, characterizes the geographic coverage of the fish collection as principally the Gulf of California and adjacent areas of the Tropical Eastern Pacific in Mexico with a significant element of freshwater fishes from Arizona and northwestern Mexico. The majority represent samples of rocky-bottom, near-shore habitats throughout the Gulf, from the mainland and Baja California shores as well as the Gulf islands. To a lesser extent, it includes fishes from seine and trawl samples of nearshore and offshore soft bottoms. These collections present a valuable ‘‘before’’ snapshot of a marine ecosystem Fig. 1. Don in his office at the University of Arizona, circa 1999. Photo by Richard Brusca.