Cardiac disorders in farmed adult brown trout, Salmo trutta L.

Abstract

During summer in Brittany, France, sea farmed brown trout, Salmo trutta L., regularly experience a high mortality rate which is associated, at least in part, with cardiac disorders (aneurysms and infarcts). The present study is preliminary to a more extensive research programme, the objective of which is to determine to what extent the physiological performance of the cardiovascular system of brown trout is affected by the environmental conditions the fish experience in farm cages. We conducted a 2-week in situ experiment during which the heart rate of eight sea water acclimatized individuals was telemetered using acoustic tags. During the experimental period, water temperature ranged from 16.0 to 17.6°C. Water oxygen saturation was above 80% at all times and salinity was very high (35.5‰) but stable. Although they were unfed and not active, seven of out the eight tagged animals displayed near maximum heart beat frequencies, which ranged between 83 and 98 beats per minute (bpm). On the other hand, the eighth animal exhibited medium-range heart rates (50-70 bpm). Using phase delay maps, we established that the maximum heart rate of brown trout at 17°C was in the range of 96 -100 bpm. This result suggests that in our experimental conditions, the heart rate of most of our inactive fish was between 85 and 100% of maximum myocardial performance. We hypothesize that the cardiac failures observed in brown trout during summer are most likely a result of strenuous workloads imposed on the cardiovascular system by a combination of elevated temperature, high salinity and possibly season-related decreased hypo-osmoregulatory abilities.

Heart morphology in wild and farmed Atlantic salmon Salmo salar and rainbow trout Oncorhynchus mykiss

“…It appears, both from our own experience as well as reports from Canada and France (Mercier et al 2000, Brocklebank & Raverty 2002) that abnormally shaped hearts and misaligned vessels might be a widespread problem that has so far been overlooked in fish farming. The reduced cardiovascular capacity might cause severe losses due to increased mortality and reduced growth rate.…”

“…These include arteriosclerosis (Farrell 2002), anomalies in heart rate (Mercier et al 2000), aplasia of septum transversum (Poppe et al 1998), situs inversus of the heart (Kaada & Hopp 1995), hypoplasia of the outer, compact ventricular myocardium (Poppe & Taksdal 2000) and cardiac hernia with myocardial hypoplasia (Poppe et al 2002). Common to all these abnormalities is restricted cardiac function, manifested by reduced tolerance to transportation, handling, grading and anaesthesia.…”

Linking swimming performance, cardiac pumping ability and cardiac anatomy in rainbow trout

“…When rainbow trout swim, or when they are given an intraarterial adrenaline injection, both Q and diastolic ventral aortic pressure increase, but mean pressure rarely exceeds 8·kPa (Kiceniuk and Jones, 1977;Gamperl et al, 1994). The heart was then returned to the control perfusion conditions for a 15·min recovery and equilibration with a new adrenaline concentration (1·µmol·l -1 ) in the perfusate, which was then used to assess the effect of maximum adrenergic stimulation of the heart (see Mercier et al, 2000). The two adrenaline concentrations used (5·nmol·l -1 and 1·µmol·l -1 ) span the range for circulating catecholamine levels observed in resting and stressed trout, respectively (Milligan et al, 1989;Randall and Perry, 1992;Gamperl et al, 1994).…”

Domestication causes rapid changes in heart and brain morphology in Atlantic cod (Gadus morhua)

“…A number of studies have reported the development of various heart deformities in salmon farmed under intensive aquaculture conditions, as a result of both hyperplasia and hypertrophy (Poppe and Taksdal 2000;Poppe et al 2002Poppe et al , 2003Gamperl and Farrell 2004;Takle et al 2006). While the most reported cardiac deformity is heart hypertrophy and altered ventricle shape (Poppe et al 2003), other reported deformities in farmed salmon include increased levels of fat deposition (Gamperl and Farrell 2004) arteriosclerosis (Farrell 2002) and anomalies in heart rate (Mercier et al 2000).…”