Yi-Jiun Tsai

• University of California, Davis

Objective Delta Smelt Hypomesus transpacificus are thought to be close to extinction in the wild, which has spurred multiagency conservation efforts to supplement their population. In conjunction with these recent efforts, monitoring is needed to assess the effectiveness of supplementation. Such monitoring often uses large‐scale tagging of released...

Objective A small‐scale culture system effective in producing larvae of endangered Delta Smelt Hypomesus transpacificus was recently developed to facilitate conservation and research efforts. Methods To optimize its use, we examined the effect of stocking density (300, 500, 700, and 900 fish per 92 L of water) on the length, weight, and survival o...

For many imperiled species, comparisons between wild and cultured populations are invaluable for informing conservation measures, though opportunities to do so may be rare. In this study, we asked whether spawning between and among wild and cultured Delta Smelt varies in terms of behavior or resulting egg fertilization success. We conducted two lab...

Delta Smelt are thought to be on the precipice of extinction. Studies that examine how this endangered species responds to environmental change are important to informing conservation efforts. In the wild, Delta Smelt are likely to encounter wide variation in the salinity of their environment that is influenced by both natural and anthropogenic fac...

Since 2008, a refuge population of Delta Smelt Hypomesus transpacificus has been cultured in a conservation hatchery to help protect the imperiled species from extinction. Culture techniques for this population have thus far focused on maximizing genetic diversity in conjunction with large‐scale operations (40 larval tanks, 5,954 L larval system, 2...

Studies of cultured populations can be invaluable to the conservation of imperiled species for which little is known and whose very low abundance in the wild can preclude studies with robust sample sizes. For example, in endangered delta smelt (Hypomesus transpacificus), conservation measures developed to mitigate population decline are hindered by...

We validated the use of diluted sodium hypochlorite solution (0.13%) for detaching eggs from surfaces and computer-aided, photograph-based counting for assessing egg fertilization success in Delta Smelt (Hypomesus transpacificus). We examined the total number of eggs counted and the proportion of eggs fertilized before and after exposure to sodium...

We examined cultured Hypomesus transpacificus under laboratory settings to provide the first formal characterization of spawning behavior, which included the quantification of participants and diel spawning patterns. We video‐recorded behavioral observation trials in which four mature males and four ripe females interacted freely for 9–11 days. We...

Very little is understood about the spawning habitat of endangered Delta Smelt Hypomesus transpacificus, which hinders ongoing recovery efforts such as wetland habitat restoration and spawning habitat augmentation. To address this, the spawning response of wild-caught H. transpacificus to different substrates and water velocities was examined acros...

Contest competition is the direct struggle for mates, resources, or both. Winning contests is thought to be determined by a competitor's fighting ability (resource-holding potential, RHP), the value of a contested resource to a competitor (resource value, RV), or both. Larger competitors' winning against smaller competitors is often explained by la...

During contest competition, a competitor may persist in a given contest based on information regarding its own fighting ability (resource-holding potential, RHP), or that of its opponent. Although a number of models formalize the ways in which competitors are hypothesized to use RHP-related information to determine their persistence in contests, we...

In this quantitative study of locational and social dispersal at the individual level, we show that bottlenose dolphins (Tursiops sp.) continued to use their natal home ranges well into adulthood. Despite substantial home range overlap, mother–offspring associations decreased after weaning, particularly for sons. These data provide strong evidence...

Few studies of kinship in mammalian societies have been able to consider the complex interactions between home range overlap, association patterns and kinship, which have created a critical gap in our understanding of social evolution. We investigated the association patterns of female bottlenose dolphins, Tursiops aduncus, in the eastern gulf of S...

The Huachuca springsnail (Pyrgulopsis thompsoni) is a species of concern inhabiting springs of the Huachuca Mountains in southeastern Arizona, USA. We documented springsnail distribution and examined the major abiotic and biotic factors influencing springsnail abundance at eight spring channels before and after the onset of seasonal summer rains in...