![]() ![]() Females have late maturity and do not breed each year. Paddlefish and sturgeons display strong spawning site fidelity, and large shoals of adults gather over clean gravel-cobble stream substrates for spawning. Sturgeon and paddlefish are vulnerable to impacts from human activities, in particular fisheries. Figure 8.2: Alligator Gar (Atractosteus spatula). Overharvest and habitat change have influenced these primitive bony fish, and the success of conservation efforts depends, in part, on changes in human attitudes that will stimulate conservation actions. ![]() 2005), and the Chinese Paddlefish was recently declared extinct (Zhang et al. However, most populations of sturgeons and paddlefish are at risk of extinction (Boreman 1997 Pikitch et al. With such a long history on Earth, one would assume that these fish are extinction proof. These primitive fish groups survived the last major extinction on Earth (66 million years ago) and persisted throughout the second age of radiation of bony fish. ![]() Paddlefish and sturgeon appeared in the fossil record 245 to 208 million years ago (Mya) near the end of the Triassic, making them among the most ancient of still-living ray-finned (actinopterygian) fish (Figure 8.1). Hence, these primitive bony fish are often referred to as fishy dinosaurs. When the first flowering plants appeared on Earth and dinosaurs were the dominant large land animals, the ancestors of gars, bowfins, sturgeons, and paddlefish swam the waters of the ancient Tethys Sea. Bowfin and gars are sister groups to all bony fish. \)Ĩ.1 The Primitive Bony Fish of North America Figure 8.1: Phylogenetic tree depicting the accepted relationships between sturgeons and paddlefish, gars, bowfins, and bony fish. ![]()
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