The behavioural, digestive and metabolic characteristics of fishes with different foraging strategies

Abstract

SUMMARYTo test the hypothesis that digestion has a more notable physiological effect on ambush foragers than on active foragers, we investigated the behavioural, digestive and metabolic characteristics, as well as the postprandial locomotory capacity, of four species of juvenile fish distributed along the Yangtze River, China, with distinct foraging strategies. The ambush foraging southern catfish (Silurus meridionlis) had the fewest movements per minute (MPM), lowest per cent time spent moving (PTM), slowest critical swimming speed (U crit ), lowest maintenance metabolism (V O2rest ) and lowest maximum locomotory metabolism (V O2max ). However, the southern catfish had the highest feeding level and maximum feeding metabolism (V O2peak ) and the greatest decrease in U crit after consumption of a large meal. Thus, this fish is highly adapted to its ambush behavioural strategy and sedentary life style. In the herbivorous grass carp (Ctenopharyngodon idellus), a low digestive capacity led to little change in postprandial locomotory performance, which benefits its frequent grazing behaviour. In this species, the greater amount of energy spent on routine activity and avoiding predators versus U crit might be related to its herbivorous life style and high predation risk. The active foraging crucian carp (Carassius auratus) adopts a unique high energy cost strategy that allows for high capacity in both routine activity and digestion, and the great flexibility of its cardio-respiratory capacity (increased V O2max after feeding) guarantees a small decrease in U crit even after maximum feeding. Finally, the sluggish foraging darkbarbel catfish (Pelteobagrus vachelli) has low digestive and locomotory capacity, but its energy-efficient venomous defence strategy may be related to its abundance. These results show that the digestive, behavioural and metabolic strategies differ among these fish species. The locomotory capacity in the sedentary fishes decreased profoundly after feeding, whereas it decreased little or not at all in the active fishes. The maintenance of high locomotory capacity after eating in the active fishes is probably related to a large metabolic capacity, a lower digestive capacity or an improvement in cardio-respiratory capacity after feeding.

Predator-driven intra-species variation in locomotion, metabolism and water velocity preference in pale chub (Zacco platypus) along a river

“…However, several species such as Siluriformes: Sisoridae maintain their position in riptide currents by attaching onto rocks through morphological specialisation (with the lips reflected and spreading to form a broad flat sucker) (Peng et al, 2004), rather than through better steady swimming performance. In addition, darkbarbel catfish (Pelteobagrus vachelli) deter predators primarily by using their spines rather than by making a speedy escape (Fu et al, 2009). In this study, the shorter response latency of highpredation pale chub may also be a specific adaptive anti-predator strategy, and this method needs further investigation.…”

Aerobic scope measurements of fishes in an era of climate change: respirometry, relevance and recommendations

“…pelagic active predators versus benthic ambush predators) use their available aerobic scope for different purposes (Table1). In less active species, higher M O2,max values may be attained during digestion alone than during aerobic swimming or following exhaustive burst swimming challenges (Fu et al, 2009a). Thus, the maximum oxygen transport capacity in these species may have evolved to accommodate the metabolic requirements during digestion of large meals while remaining relatively inactive, rather than to maintain a high aerobic scope during continuous swimming (Table1).…”

Finding the best estimates of metabolic rates in a coral reef fish

“…Ten fish (TL=17.6±0.4cm, M=97.0±7.7g; means ± s.d.) were subjected to each of three protocols in a random order: a U crit trial (Brett, 1964;Beamish, 1978;Johansen and Jones, 2011), a 15min exhaustive chase trial (see Cutts et al, 2002;Killen et al, 2007;Fu et al, 2009;Norin and Malte, 2011;Shultz et al, 2011) and a 3min exhaustive chase followed by a 1min air exposure trial (Ferguson and Tufts, 1992;Donaldson et al, 2010;Clark et al, 2012). The same fish (N=10) were subjected to each protocol following a repeated-measures design (Reidy et al, 1995) to minimize interindividual variation in metabolic rates.…”

“…The first consisted of a 15min exhaustive chase trial in which individual fish were placed in a 110cm diameter circular tank and chased continuously with a 20mm diameter PVC tube until exhaustion (i.e. all fish became unresponsive within 12-15min) (see Cutts et al, 2002;Fu et al, 2006;Killen et al, 2007;Fu et al, 2009;Norin and Malte, 2011). The experimenter would only touch the tail of the fish if it slowed down or stopped swimming.…”