Heather A. Stewart

Florida Fish and Wildlife Conservation Commission | ffwcc · Fish and Wildlife Research Institute

Foundation species structure communities by creating habitat and modifying environmental conditions, and there is increasing interest in how foundation species, such as corals and mangroves, interact with one another as these interactions can have cascading effects on diversity and abundance of associated organisms. Given recent reports of corals l...

Unprovoked mouth gaping behavior is ubiquitous throughout 24 extant members of Crocodylia, yet information on gaping is limited. Proposed hypotheses for gaping include thermoregulation and the evaluation of potential environmental conditions. To determine temperature effects, we tracked head surface (Tsh), body surface (Tsb), and ambient (Ta) tempe...

Mangrove ecosystems in the Caribbean are frequently exposed to hurricanes, leading to structural and regenerative change that elicit calls for recovery action. For those mangroves unaffected by human modifications, recovery can occur naturally. Indeed, observable natural recovery after hurricanes is the genesis of the “disturbance adaptation” class...

We conducted visual fish surveys in coexisting mangrove‐coral (CMC) habitats in Panama to analyze the effect of coral presence in mangrove habitats on the fish assemblage. Our study revealed that CMC habitats harbor distinct fish assemblages compared to mangrove habitats without coral, with greater species richness and increased herbivore abundance...

Marine ecosystems are structured by coexisting species occurring in adjacent or nested assemblages. Mangroves and corals are typically observed in adjacent assemblages (i.e., mangrove forests and coral reefs) but are increasingly reported in nested mangrove-coral assemblages with corals living within mangrove habitats. Here we define these nested a...

Foundation species traits that structure communities are rarely experimentally examined; thus, a predictive understanding of their functions lags behind patterns of observed species associations. Red mangrove Rhizophora mangle roots form complex living habitats that support diverse epibiont communities, making them a model system for testing links...

The Channel Catfish Ictalurus punctatus is an important ecological, recreational and aquaculture species. In both natural and pond culture systems, Channel Catfish are periodically exposed to acute increase in temperature, especially in the summer, which may induce a stress response. With the effects of global climate change, the impact of rising t...

Pectoral fin healing in fin spines and rays were examined in juvenile Atlantic sturgeon Acipenser oxyrinchus oxyrinchus following three different sampling techniques (n = 8–9 fish per treatment): entire leading fin spine removed, a 1–2 cm portion removed near the point of articulation, or a 1–2 cm portion removed from a secondary fin ray. Also, to...

Variation in early life history traits often leads to differentially expressed morphological and behavioral phenotypes. We investigated whether variation in egg size and emergence timing influence subsequent morphology associated with migration timing in juvenile spring Chinook Salmon, Oncorhynchus tshawytscha. Based on evidence for a positive rela...

Seasonal timing of transportation and acclimation of juvenile Chinook salmon (Oncorhynchus tshawytscha) between hatcheries may affect osmoregulation and survival. We investigated the duration of time fish need to acclimate to hatchery conditions prior to being presented with a saltwater challenge. We monitored acute survival and osmoregulatory abil...

The Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus Mitchill, 1815) is an anadromous sturgeon species, yet little is known with regard to its osmoregulatory ability and habitat use at early life stages. In order to examine whether salinity poses a physiological challenge to juvenile Atlantic sturgeon near the sizes where they may begin to move i...

Climate change due to anthropogenic activity will continue to alter the chemistry of the oceans. Future climate scenarios indicate that sub-tropical oceans will become more acidic, and the temperature and salinity will increase relative to current conditions. A large portion of previous work has focused on how future climate scenarios may impact sh...

The movement of Muskellunge Esox masquinongy over a dam to leave a reservoir is known as dam escape. It is common in Midwestern U.S. reservoirs and has been as high as 25% of the adult population. A variety of barrier and guidance systems have been used to control fish movement, but the success of such barriers has been mixed and appears to be very...

Field sampling techniques may cause damage to fins either directly by tissue removal for ageing or genetic purposes or indirectly during capture and handling. To assess how fins heal following different sampling techniques, three different pectoral fin spine/ray treatments were applied (n=8-9 fish/trt): entire leading fin ray removed, a 1-2 cm port...

Climate change is a growing concern for pond culture of catfish, due to possible exacerbation of temperature fluctuations and increased maximum daily temperatures. Because channel catfish (Ictalurus punctatus) have a broad natural distribution from Canada to Mexico, it was hypothesized that natural differences in thermal tolerance and seasonal grow...

Critical thermal maxima have been used extensively to provide physiologically and ecologically valuable reference points that identify early signs of thermal stress. In catfish pond culture, daily temperature maxima up to 36°C and daily fluctuations of as much as 6°C are observed. These extreme conditions will probably be exacerbated by the effects...

Global climate change is a growing concern for pond culture due to possible exacerbation of temperature fluctuations and increased maximum daily temperatures. Channel catfish (Ictalurus punctatus) have a broad natural distribution from southern Canada to northern Mexico. It was hypothesized that natural differences in thermal tolerance and seasonal...