Bioenergetics assessment of fish and crayfish consumption by river otter (Lontra canadensis): integrating prey availability, diet, and field metabolic rate

Abstract

River otters ( Lontra canadensis ) are important predators in aquatic ecosystems, but few studies quantify their prey consumption. We trapped crayfish monthly as an index of availability and collected otter scat for diet analysis in the Ozark Mountains of northwestern Arkansas, USA. We measured otter daily energy expenditure (DEE) with the doubly labeled water method to develop a bioenergetics model for estimating monthly prey consumption. Meek’s crayfish ( Orconectes meeki ) catch-per-unit-effort was positively related to stream temperature, indicating that crayfish were more available during warmer months. The percentage frequency of occurrence for crayfish in scat samples peaked at 85.0% in summer and was lowest (42.3%) in winter. In contrast, the percentage occurrence of fish was 13.3% in summer and 57.7% in winter. Estimates of DEE averaged 4738 kJ·day–1 for an otter with a body mass of 7842 g. Total biomass consumption ranged from 35 079 to 52 653 g·month–1 (wet mass), corresponding to a high proportion of fish and crayfish in the diet, respectively. Otter consumption represents a large fraction of prey production, indicating potentially strong effects of otters on trophic dynamics in stream ecosystems.

Move or die: change in European catfish (Silurus glanisL.) behaviour caused by oxygen deficiency

“…This low physiological activity may result in higher predation by homoeothermic predators such as birds or mammals (Stewart et al, 2005;Dekar et al, 2010). However, there is a more serious threat affecting the fish stock during winter in some localities; namely, oxygen deficiency.…”

Summer Diet Characteristics of North American River Otters (Lontra canadensis) in Central Illinois

“…As in other studies, fish was the most common prey although the types of fish represented in the Emiquon diets differed. While centrarchids (e.g., sunfish) were the most common at Whiteside County and Arkansas and catostomids (e.g., suckers) were the most common in Alberta, cyprinids (e.g., carp and minnows) were the most commonly represented group at Emiquon (Anderson and Woolf, 1987b;Reid et al, 2004;Dekar et al, 2010). This is largely due to the dominant presence of a single species, common carp at Emiquon.…”

“…The change in prey type frequency over time (e.g., seasons or months) at Emiquon has been found to occur elsewhere. In Arkansas, crayfish activity increased with water temperature, which provided river otters opportunities to prey on crayfish more than fish in the summer as they were more active and vulnerable to predation (Dekar et al, 2010). In winter, however, fish were the dominant prey type (Dekar et al, 2010).…”

“…In Arkansas, crayfish activity increased with water temperature, which provided river otters opportunities to prey on crayfish more than fish in the summer as they were more active and vulnerable to predation (Dekar et al, 2010). In winter, however, fish were the dominant prey type (Dekar et al, 2010). Similarly, in Missouri and North Dakota, fish were less important prey in summer when crayfish were consumed the most frequently (Roberts et al, 2008;Stearns and Serfass, 2011).…”

“…They have been known to consume between 35 to 52 kg of total biomass per month (Dekar et al, 2010). Prey of otters is diverse and includes fish, amphibians, crustaceans, small mammals, reptiles, birds, mollusks, clams, and aquatic insects (Hoffmeister, 1989;Hofmann, 2010; Barding and Lacki, 2012).…”