Jeroen Brijs

University of Innsbruck | UIBK · Institute of Zoology

Species invasions are a global problem of increasing concern, especially in highly connected aquatic environments. Despite this, salinity conditions can pose physiological barriers to their spread and understanding them is important for management. In Scandinavia’s largest cargo port, the invasive round goby (Neogobius melanostomus), is established...

Both percussive and electrical stunning have been highlighted as methods that can be used to quickly render fish unconscious before being killed. However, accurately assessing unconsciousness in animals following stunning remains challenging, and thus methods for reliable interpretation and validation of different stunning methods are urgently need...

Farmed aquatic animals represent an increasingly important source of food for a growing human population. However, the aquaculture industry faces several challenges with regard to producing a profitable, ethical and environmentally sustainable product, which are exacerbated by the ongoing intensification of operations and increasingly extreme and u...

European whitefish (Coregonus lavaretus) is an aquaculture species with the potential for expanded cultivation in the fresh and brackish waters of Northern Europe. Yet, relatively little species-specific information is available regarding the stress responses and associated welfare implications for this species in captivity. We addressed this knowl...

Few studies have addressed how reduced water salinity affects cardiovascular and metabolic function in marine euryhaline fishes, despite its relevance for predicting impacts of natural salinity variations and ongoing climate change on marine fish populations. Here, shorthorn sculpin (Myoxocephalus scorpius) were subjected to different durations of...

Common slaughter procedures for African sharptooth catfish (Clarias gariepinus) include asphyxiation, ice chilling and exsanguination, which may all cause substantial suffering over prolonged periods of time before death. Therefore, comprehensive evaluations of potentially more humane slaughter procedures for this species are urgently needed. Here,...

Cardiovascular disease may pose a major threat to the health and welfare of farmed fish. By investigating a range of established cardiovascular disease indicators, we aimed to determine the prevalence, severity and consequences of this affliction in farmed rainbow trout (Oncorhynchus mykiss) from an open cage farm in the Baltic Sea, an open cage fa...

Bio-logging devices can provide unique insights on the life of freely moving animals. However, implanting these devices often requires invasive surgery that causes stress and physiological side-effects. While certain medications in connection to surgeries have therapeutic capacity, others may have aversive effects. Here, we hypothesized that the co...

Blood doping, the practice of boosting the oxygen carrying capacity of blood, is an illegal strategy used by human athletes to enhance aerobic capacity and athletic performance. Interestingly, the practice of boosting blood oxygen carrying capacity is also naturally prevalent in the animal kingdom via the splenic release of stored erythrocytes. Her...

Investigating the mechanisms that fish employ to maintain homeostasis in their everyday life requires measurements of physiological and behavioural responses in the field. With multivariate bio-loggers, we continuously measured gastrointestinal blood flow (GBF), heart rate, activity and body temperature in rainbow trout (Oncorhynchus mykiss) swimmi...

Investigating real-time stress responses during common aquaculture practices is necessary for improving the welfare of farmed fish. Recently, Star-Oddi DST milli-HRT bio-loggers capable of measuring heart rate (as an indicator for stress) in freely swimming fish have proved to be useful in this regard. However, despite the growing popularity of the...

Phenotypic scoring of wild animals under standardized laboratory conditions is important as it allows field ecologists and evolutionary biologists to understand the development and maintenance of interindividual differences in plastic traits (e.g. behaviour and physiology). However, captivity is associated with a shift from a natural familiar envir...

Greater salinity variations resulting from ongoing climate change requires consideration in conservation management as this may impact on the performance of aquatic organisms. Euryhaline fish exhibit osmoregulatory flexibility and can exploit a wide range of salinities. In seawater (SW), they drink and absorb water in the intestine, which is associ...

Cardiac oxygenation is achieved via both coronary arterial and luminal venous oxygen supply routes in many fish species. However, the relative importance of these supplies for cardiac and aerobic metabolic performance is not fully understood. Here, we investigated how coronary artery ligation in rainbow trout (Oncorhynchus mykiss), implanted with h...

The aim of the current work was to elucidate if there is a connection between stress‐induced decrease in coeliacomesenteric artery blood flow (i.e. gastrointestinal blood flow; GBF) and disruption of the intestinal primary barrier in rainbow trout Oncorhynchus mykiss. Upon initiation of a 15 min acute chasing stress, the GBF decreased instantly by...

The fish gut is responsible for numerous potentially energetically costly processes, yet little is known about its metabolism. Here, we provide the first in vivo measurements of aerobic metabolism of the gut in a teleost fish by measuring gut blood flow, as well as arterial and portal venous oxygen content. At 10°C, gut oxygen uptake rate was 4.3±0...

The Commentary by Pörtner, Bock and Mark (Pörtner et al., 2017) elaborates on the oxygen- and capacity-limited thermal tolerance (OCLTT) hypothesis. Journal of Experimental Biology Commentaries allow for personal and controversial views, yet the journal also mandates that ‘opinion and fact must be clearly distinguishable’ (http://jeb.biologists.org...

Upon exposure to seawater, euryhaline teleosts need to imbibe and desalinate seawater to allow for intestinal ion and water absorption, as this is essential for maintaining osmotic homeostasis. Despite the potential benefits of increased mixing and transport of imbibed water for increasing the efficiency of absorptive processes, the effect of water...

Gill parasites on fish are likely to negatively influence their host by inhibiting respiration, oxygen transport capacity and overall fitness. The glochidia larvae of the endangered freshwater pearl mussel (FPM, Margaritifera margaritifera (Linnaeus, 1758)) are obligate parasites on the gills of juvenile salmonid fish. We investigated the effects o...

Anadromy is a distinctive life-history strategy in fishes that has evolved independently many times. In an evolutionary context, the benefits of anadromy for a species or population must outweigh the costs and risks associated with the habitat switch. The migration of fish across the freshwater-ocean boundary coincides with potentially energeticall...

1.A phenotypic syndrome refers to complex patterns of integration among functionally related traits in an organism that defines how the organism interacts with its environment and sustains itself. 2.Human-induced biological invasions have become important sources of environmental modifications. However, the extent to which invasive species affect...

Cellular and mitochondrial metabolic capacity of the heart has been suggested to limit performance of fish at warm temperatures. We investigated this hypothesis by studying the effects of acute temperature increases (16, 23, 30, 32.5 and 36°C) on the thermal sensitivity of 10 key enzymes governing cardiac oxidative and glycolytic metabolism in two...

Substantial increases in cardiac output (CO), stroke volume (SV) and gastrointestinal blood flow are essential for euryhaline rainbow trout (Oncorhyncus mykiss) osmoregulating in seawater. However, the underlying hemodynamic mechanisms responsible for these changes are unknown. By examining a range of circulatory and cardiac morphological variables...

Substantial increases in cardiac output (CO), stroke volume (SV), and gastrointestinal blood flow are essential for euryhaline rainbow trout (Oncorhyncus mykiss) osmoregulation in seawater. However, the underlying hemodynamic mechanisms responsible for these changes are unknown. By examining a range of circulatory and cardiac morphological variable...

Rhythmic contractions of the mammalian gastrointestinal tract can occur in the absence of neuronal or hormonal stimulation due to the generation of spontaneous electrical activity by interstitial cells of Cajal (ICC) that are electrically coupled to smooth muscle cells. The myogenically-driven component of gastrointestinal motility patterns in fish...

Thermal plasticity of cardiorespiratory function allows ectotherms like fish to cope with seasonal temperature changes and is critical for resilience to climate change. Yet, the chronic thermal effects on cardiovascular homeostatic reflexes in fish are little understood although this may have important implications for physiological performance and...

Oxygen supply to the heart has been hypothesized to limit cardiac performance and whole animal acute thermal tolerance (CTmax) in fish. We tested these hypotheses by continuously measuring venous oxygen tension (PVO2) and cardiovascular variables in vivo during acute warming in European perch (Perca fluviatilis) from a reference area during summer...

Understanding the resilience of aquatic ectothermic animals to climate warming has been hindered by the absence of experimental systems experiencing warming across relevant timescales (for example, decades). Here, we examine European perch (Perca fluviatilis, L.) from the Biotest enclosure, a unique coastal ecosystem that maintains natural thermal...

Supplementary Figures 1-3 and Supplementary Tables 1-4.

Increased gastrointestinal blood flow is essential for euryhaline fishes to maintain osmotic homeostasis during the initial phase of a transition from freshwater to seawater. However, the cardiorespiratory responses and hemodynamic changes required for a successful long-term transition to seawater remain largely unknown. In the present study, we si...

A progressive inability of the cardiorespiratory system to maintain systemic oxygen supply at elevated temperatures has been suggested to reduce aerobic scope and the upper thermal limit of aquatic ectotherms. However, few studies have directly investigated the dependence of thermal limits on oxygen transport capacity. By manipulating oxygen availa...

The large-scale migrations of anadromous fish species from freshwater to seawater have long been considered particularly enigmatic, as this life history necessitates potentially energetically costly changes in behaviour and physiology. A significant knowledge gap concerns the integral role of cardiovascular responses, which directly link many of th...

This is the first study to catalogue the diverse array of in vivo motility patterns in a teleost fish and how they are affected by feeding. Video recordings of exteriorised proximal intestine from fasted and fed shorthorn sculpin (Myoxocephalus scorpius) were used to generate spatio-temporal maps to portray and quantify motility patterns. Propagati...

We conducted a boat electrofishing survey of the Ohau Channel, which flows from Lake Rotorua to Lake Rotoiti, on 7 December 2009. The purpose of this was to repeat surveys that took place on 13 December 2007 and 11 December 2008 concerning the longitudinal pattern in densities of common smelt (Retropinna retropinna) and common bully (Gobiomorphus c...

Lake Rotokaeo (Forest Lake) is a small (3.7 ha) lake set in suburban surroundings in the north-west of Hamilton city located at 37° 46.387’S and 175° 15.059’E. The lake is very shallow, with ~80% of its area <1.8 m water depth, depending on season. The bed is composed of soft sediments, and margins vary from grassed parkland to restored native wetl...

The upper Turitea Reservoir is a 12-ha reservoir that supplies water to the city of Palmerston North (Figure 1). It was constructed in 1957 and is located in the foothills of the Tararua Ranges at 40.43208°S, 175,67669°E. The 2,300 hectare catchment area is comprised mainly of native forest with a small section of pine forest bordering the northern...

We conducted a boat electrofishing survey of the Ohau Channel, which flows from Lake Rotorua to Lake Rotoiti, on 11 December 2008. The purpose of this was to repeat a survey that took place on 13 December 2007 concerning the longitudinal pattern in densities of common smelt (Retropinna retropinna) and common bully (Gobiomorphus cotidianus). We caug...

New Zealand's five endemic mudfish (Neochanna spp.) species have distributions that differ both geographically and by habitat type. Differences in habitat preferences between species have led to the proposal of an evolutionary series within the group. A morphological cline can be observed from the galaxiform Chatham Island and Canterbury species in...

We conducted a fish survey of five ponds (Lake Panorama, Paremuka Pond 1 & 2, Danica Esplanade and Longbush Pond) in the Waitakere District by single-pass boat electrofishing on 18 and 19 of July 2007. We caught 337 fish comprising four introduced and two native fish species in 2.89 km of fished distance from all 5 ponds. Assuming that each of the...

The koi carp is an ornamental strain of the common carp (Cyprinus carpio) which is believed to be one of the most ecologically detrimental of all freshwater invasive fish species. They are widespread in the Auckland and Waikato region and appear to be spreading both north and south of these areas. The presence of koi carp in 3 ornamental ponds at K...

The koi carp is an ornamental strain of the common carp which is believed to be one of the most ecologically detrimental of all freshwater invasive fish species. Numerous “koi carp” sightings have been made by the public in the Holowhitu Lagoon, Palmerston North. Because koi carp is designated an unwanted organism under the Biosecurity Act, the Dep...

Tenagomysis chiltoni, a species of mysid shrimp, is widely distributed amongst the riverine lakes of the lower Waikato basin. They appear to thrive in turbid waters, with the greatest abundances found in lakes such as Waahi and Waikare, which have low Secchi transparencies and sparse aquatic macrophyte communities representing remnants of formerly...