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Despite decades of commercial harvest of bigmouth buffalo (Ictiobus cyprinellus) from Jamestown Reservoir, North Dakota, and the recent rapid growth of sport bowfishing that targets this species, there is a lack of biological information on this native catostomid. At present, no-limit recreational and commercial harvest of bigmouth buffalo occurs in North Dakota, with no harvest-reporting for recreational take. A long-lived life history was recently documented for this species, with a life-span exceeding 100 years. At Jamestown Reservoir, bigmouth buffalo were aged to 58 years of age, with onset of sexual maturity 10 years for females. Evidence for episodic recruitment over a 60-year period was in 1962–1979, 1993–2011, and 2017, with recruitment success more likely during non-drought periods. Annual commercial harvest data from this reservoir indicate bigmouth buffalo have declined significantly over the past 30 years, most precipitously since 2010 during the bowfishing era. The demographic patterns, episodic recruitment, and harvest changes observed in this population are relevant for informing management of bigmouth buffalo and other long-lived freshwater fishes.

Although the pace of senescence varies considerably, the physiological systems that contribute to different patterns of senescence are not well understood, especially in long-lived vertebrates. Long-lived bony fish (i.e., Class Osteichthyes) are a particularly useful model for studies of senescence because they can readily be aged and exhibit some of the longest lifespans among vertebrates. In this study we examined the potential relationship between age and multiple physiological systems including: stress levels, immune function, and telomere length in individuals ranging in age from 2 to 99 years old in bigmouth buffalo (Ictiobus cyprinellus), the oldest known freshwater teleost fish. Contrary to expectation, we did not find any evidence for age-related declines in these physiological systems. Instead, older fish appeared to be less stressed and had greater immunity than younger fish, suggesting age-related improvements rather than declines in these systems. There was no significant effect of age on telomeres, but individuals that may be more stressed had shorter telomeres. Taken together, these findings suggest that bigmouth buffalo exhibit negligible senescence in multiple physiological systems despite living for nearly a century.

Studies on the auditory system of fishes can provide fundamental information about the early evolution of vertebrate hearing. While there are limited data available on the auditory system of bony fishes, comparatively far less is known about auditory structures in elasmobranchs, despite their critical basal position within vertebrate evolution. Specifically, while there is a high degree of plasticity in the nervous system, little is known about how the different sensory epithelia within the inner ear vary throughout life in elasmobranchs. Using a combination of immunohistochemistry and fluorescence microscopy, we quantified macular area, number of sensory hair cells, hair cell density, and hair cell orientations in the saccule, lagena, utricle, and macula neglecta of school sharks (Galeorhinus galeus) of varying body size. In all maculae, macular area and the number of hair cells increased significantly throughout ontogeny, while hair cell density displayed a concurrent ontogenetic decrease (excluding the utricle). There were also significant differences in macular area, hair cell number, and hair cell density between the four maculae. However, hair cell orientation patterns did not vary between individuals and did not change with body growth. These findings represent one of the first comprehensive characterisations of the inner ear sensory epithelia in an elasmobranch, and reveal changes in morphology that may have implications for auditory capabilities through ontogeny.