The stress and metabolic responses of juvenile Atlantic cod Gadus morhua L. to an acute thermal challenge

Survival, oxygen consumption (M_O2), total plasma cortisol and glucose levels and gill heat-shock protein 70 (hsp70) expression were measured in 10 and 50 g juvenile Atlantic cod Gadus morhua during an acute temperature increase (2° C h⁻¹) to their critical thermal maximum. Ninety three per cent of the fish in both size classes survived to 24° C; however, mortality was 100% within 15 min of reaching this temperature. The M_O2 for both size classes increased significantly with temperature, reaching peak values at 22° C that were c. 2·8-fold those of control (10° C) fish. Resting plasma cortisol and glucose levels were lower in 10 g as compared to 50 g fish. Plasma glucose levels were highly variable in both size classes, and significant increases were only seen at >22° C for the 10 g fish. In contrast, plasma cortisol showed an exponential increase with temperature starting at 16° C in both size classes, and reached maximum levels at 22° C that were 19-fold (10 g fish) and 35-fold (50 g fish) higher than their respective control groups. Both the constitutive (73 kDa) and inducible (72 kDa) isoforms of hsp70 were detected in both size classes using the widely utilized mouse monoclonal antibody. Expression of these isoforms, however, did not change when Atlantic cod were exposed to elevated temperature, and the 72 kDa isoform was not detected using salmonid-specific antibodies. These results indicate that juvenile Atlantic cod are very sensitive to acute increases in water temperature. In addition, they (1) show that M_O2and plasma cortisol, but not plasma glucose or gill hsp 70 levels, are sensitive indicators of thermal stress in Atlantic cod and (2) support previous reports that the upper critical temperature for this species is 16° C.

Perspectives of sporting opportunities for remote indigenous Cape York communities

The health outcomes for Indigenous peoples are well publicised as being poorer than that of the rest of the Australian population. The importance of physical activity as part of a balanced approach to health and wellbeing are well documented. Physical inactivity is a significant risk factor for many preventable diseases that many non-Indigenous, but specifically more Indigenous peoples die from. A recent report on Indigenous health indicated that only 23% of adults living in remote and very remote areas, such as Cape York, participated in regular physical activity. Physical activity initiatives in remote Indigenous communities on Cape York are commonly delivered by external agencies that ‘fly in and fly out’. While members of Indigenous communities may engage with the initiatives while they are being provided once the external agencies leave some of the benefits made may be quickly lost. There is no current published literature on the variety, prevalence and outcomes of ‘fly-in fly-out’ physical activity programs, or on the agencies that provide them. An understanding of these factors would facilitate a better understanding of the opportunities available to Indigenous communities on Cape York and provide important foregrounding to an investigation of community capacity for physical activity. The purpose of this study was to investigate the range of physical activity programs being offered by external agencies to Indigenous Cape York communities.

Methods: Five physical activity agencies that routinely engaged with Indigenous communities on Cape York were interviewed. The semi-structured interviews focussed on what activities were being conducted; by whom; when; and their concomitant outcomes. Interviews were recorded and professionally transcribed. Transcriptions were then analysed using content analysis to identify themes.

Results: Each physical activity agency had a variety of ways of engaging with community. The key initial focus point for each provider was the local school. Contacts within the school and opportunities to provide workshop opportunities for the students then facilitated wider community engagement.

Discussion: There were limited opportunities for these agencies to build community capacity to maintain their physical activities due to a variety of reasons that included: resources (both human and material); transient populations and an entrenched culture of ‘having things done to’ rather than with Indigenous people. In order to improve the physical activity outcomes of Indigenous people on Cape York community’s strategies that engage and empower the local population to take control of their needs should be employed.

Link between vertical and horizontal movement patterns of cod in the North Sea

We used a geolocation method based on tidal amplitude and water depth to assess the horizontal movements of 14 cod Gadus morhua equipped with time-depth recorders (TDR) in the North Sea and English Channel. Tracks ranged from 40 to 468 d and showed horizontal movements of up to 455 km and periods of continuous localised residence of up to 360 d. Cod spent time both in midwater (43% of total time) and near the seabed (57% of total time). A variety of common vertical movement patterns were seen within periods of both residence and directed horizontal movement. Hence particular patterns of vertical movement could not unequivocally define periods of migration or localised residence. After long horizontal movements, cod tended to adopt resident behaviour for several months and then return to broadly the same location where they were tagged, indicating a geospatial instinct. The results suggest that residence and homing behaviour are important features of Atlantic cod behaviour.

Vertical movements of North Sea Cod

Various air-breathing marine vertebrates such as seals, turtles and seabirds show distinct patterns of diving behaviour. For fish, the distinction between different vertical behaviours is often less clear-cut, as there are no surface intervals to differentiate between dives. Using data from acoustic tags (n = 23) and archival depth recorders attached to cod Gadus morhua (n = 92) in the southern North Sea, we developed a quantitative method of classifying vertical movements in order to facilitate an objective comparison of the behaviour of different individuals. This method expands the utilisation of data from data storage tags, with the potential for a better understanding of fish behaviour and enhanced individual based behaviour for improved ecosystem modelling. We found that cod were closely associated with the seabed for 90% of the time, although they showed distinct seasonal and spatial patterns in behaviour. For example, cod tagged in the southern North Sea exhibited high rates of vertical movement in spring and autumn that were probably associated with migration, while the vertical movements of resident cod in other areas were much less extensive and were probably related to foraging or spawning behaviours. The full reasons underlying spatial and temporal behavioural plasticity by cod in the North Sea warrant further investigation.

Application of a quantitative histological health index for Antarctic rock cod (Trematomus bernacchii) from Davis Station, East Antarctica

A quantitative Histological Health Index (HHI) was applied to Antarctic rock cod (Trematomus bernacchii) using gill, liver, spleen, kidney and gonad to assess the impact of wastewater effluent from Davis Station, East Antarctica. A total of 120 fish were collected from 6 sites in the Prydz Bay region of East Antarctica at varying distances from the wastewater outfall. The HHI revealed a greater severity of alteration in fish at the wastewater outfall, which decreased stepwise with distance. Gill and liver displayed the greatest severity of alteration in fish occurring in close proximity to the wastewater outfall, showing severe and pronounced alteration respectively. Findings of the HHI add to a growing weight of evidence indicating that the current level of wastewater treatment at Davis Station is insufficient to prevent impact to the surrounding environment. The HHI for T. bernacchii developed in this study is recommended as a useful risk assessment tool for assessing in situ, sub-lethal impacts from station-derived contamination in coastal regions throughout Antarctica.

A colostrum trypsin inhibitor gene expressed in the Cape fur seal mammary gland during lactation

The colostrum trypsin inhibitor (CTI) gene and transcript were cloned from the Cape fur seal mammary gland and CTI identified by in silico analysis of the Pacific walrus and polar bear genomes (Order Carnivora), and in marine and terrestrial mammals of the Orders Cetartiodactyla (yak, whales, camel) and Perissodactyla (white rhinoceros). Unexpectedly, Weddell seal CTI was predicted to be a pseudogene. Cape fur seal CTI was expressed in the mammary gland of a pregnant multiparous seal, but not in a seal in its first pregnancy. While bovine CTI is expressed for 24-48h postpartum (pp) and secreted in colostrum only, Cape fur seal CTI was detected for at least 2-3months pp while the mother was suckling its young on-shore. Furthermore, CTI was expressed in the mammary gland of only one of the lactating seals that was foraging at-sea. The expression of β-casein (CSN2) and β-lactoglobulin II (LGB2), but not CTI in the second lactating seal foraging at-sea suggested that CTI may be intermittently expressed during lactation. Cape fur seal and walrus CTI encode putative small, secreted, N-glycosylated proteins with a single Kunitz/bovine pancreatic trypsin inhibitor (BPTI) domain indicative of serine protease inhibition. Mature Cape fur seal CTI shares 92% sequence identity with Pacific walrus CTI, but only 35% identity with BPTI. Structural homology modelling of Cape fur seal CTI and Pacific walrus trypsin based on the model of the second Kunitz domain of human tissue factor pathway inhibitor (TFPI) and porcine trypsin (Protein Data Bank: 1TFX) confirmed that CTI inhibits trypsin in a canonical fashion. Therefore, pinniped CTI may be critical for preventing the proteolytic degradation of immunoglobulins that are passively transferred from mother to young via colostrum and milk.