Geology topics

Sarah M. Laske

Publications and source records attributed to Sarah M. Laske.

21 records · Page 2Linked to original sources

USGS2018

Generalist feeding strategies in Arctic freshwater fish: A mechanism for dealing with extreme environments

Generalist feeding strategies are favoured in stressful or variable environments where flexibility in ecological traits is beneficial. Species that feed across multiple habitat types and trophic levels may impart stability on food webs through the use of readily available, alternative energy pools. In lakes, generalist fish species may take advantage of spatially and temporally variable prey by consuming both benthic and pelagic prey to meet their energy demands. Using stomach content and stable isotope analyses, we examined the feeding habits of fish species in Alaska's Arctic Coastal Plain (ACP) lakes to determine the prevalence of generalist feeding strategies as a mechanism for persistence in extreme environments (e.g. low productivity, extreme cold and short growing season). Generalist and flexible feeding strategies were evident in five common fish species. Fish fed on benthic and pelagic (or nektonic) prey and across trophic levels. Three species were clearly omnivorous, feeding on fish and their shared invertebrate prey. Dietary differences based on stomach content analysis often exceeded 70%, and overlap in dietary niches based on shared isotopic space varied from zero to 40%. Metrics of community‐wide trophic structure varied with the number and identity of species involved and on the dietary overlap and niche size of individual fishes. Accumulation of energy from shared carbon sources by Arctic fishes creates redundancy in food webs, increasing likely resistance to perturbations or stochastic events. Therefore, the generalist and omnivorous feeding strategies employed by ACP fish may maintain energy flow and food web stability in extreme environments.

Ecology of Freshwater Fish↗

USGS2017

Top-down control of invertebrates by Ninespine Stickleback in Arctic ponds

Despite their widespread presence in northern-latitude ecosystems, the ecological role of Ninespine Stickleback Pungitius pungitius is not well understood. Ninespine Stickleback can occupy both top and intermediate trophic levels in freshwater ecosystems, so their role in food webs as a predator on invertebrates and as a forage fish for upper level consumers probably is substantial. We introduced Ninespine Sticklebacks to fishless ponds to elucidate their potential effects as a predator on invertebrate communities in Arctic lentic freshwaters. We hypothesized that Ninespine Stickleback would affect freshwater invertebrate communities in a top-down manner. We predicted that the addition of Ninespine Sticklebacks to fishless ponds would: 1) reduce invertebrate taxonomic richness, 2) decrease overall invertebrate abundance, 3) reduce invertebrate biomass, and 4) decrease average invertebrate body size. We tested our hypothesis at 2 locations by adding Ninespine Stickleback to isolated ponds and compared invertebrate communities over time between fish-addition and fishless control ponds. Ninespine Sticklebacks exerted strong top-down pressure on invertebrate communities mainly by changing invertebrate taxonomic richness and biomass and, to a lesser extent, abundance and average invertebrate size. Our results supported the hypothesis that Ninespine Stickleback may help shape lentic food webs in the Arctic.

Alaska↗

USGS2016

Surface water connectivity drives richness and composition of Arctic lake fish assemblages

Surface water connectivity can influence the richness and composition of fish assemblages, particularly in harsh environments where colonisation factors and access to seasonal refugia are required for species persistence. Studies regarding influence of connectivity on Arctic fish distributions are limited and are rarely applied to whole assemblage patterns. To increase our understanding of how surface water connectivity and related hydrologic variables influence assemblage patterns, we investigated species richness and composition of Arctic lake fishes over a large region, 8500 km 2 , of the central Arctic Coastal Plain, Alaska. We collected fish presence/non-detection data from 102 lakes and used a hierarchical multispecies occupancy framework to derive species richness and inform species composition patterns. Our mean estimate of regional richness was 12.3 (SD 0.5) species. Presence of a permanent channel connection was an overriding factor affecting species richness (mean 3.6, 95% CI 3.1–4.9), presumably driving lake colonisation potential. In lakes without a permanent channel connection, data suggest richness (mean 2.0, 95% CI 1.7–3.3) increased with the availability of in-lake winter refugia and with the potential of ephemeral connections during spring floods. Fish species functional traits and environmental faunal filters contributed to patterns of richness and assemblage composition. Composition corresponded with richness in a coherent manner, where each successive level of richness contained several discrete assemblages that showed similar responses to the environment. Lakes with permanent channel connections contained both widespread and restricted species, while the species-poor lakes that lacked a connection contained mainly widespread species. This work provides useful baseline information on the processes that drive the relations between patch connectivity and fish species richness and assemblage composition. The environmental processes that organise fish assemblages in Arctic lakes are likely to change in a warming climate.

Freshwater Biology↗