Assessing the environmental and ecological drives of interannual variability in the life histories and population dynamics of icefishes (Family Channichthyidae) around the sub-Antarctic Island of South Georgia.

Overview

In the Southern Ocean, there are key knowledge gaps in our understanding of life history processes and how interannual variability influences demographic properties of the endemic fish fauna. A detailed knowledge of life history processes is vital for understanding how different species with differing ecological niches will respond to interannual and longer-term variability in environmental conditions (e.g. temperature, primary productivity). Environmental change can impact marine communities at different spatial and temporal scales. This impact may not be uniform across all species and may lead to different species responding differently to changes in environmental conditions at regional and oceanic scales. Interannual variability in environmental conditions can lead to differences in timing and intensity of spawning, recruitment success and growth rates among marine species. On top of this, large-scale climate oscillations (e.g. ENSO) and oceanic warming can lead to longer term changes in the abundance, distribution and depth range of marine species. The endemic suborder Notothenioidei which dominates the fish fauna on the Southern Ocean continental shelves will potentially be susceptible to large-scale and regional warming. The Notothenioidei have specific adaptations to live in the cold waters of the Southern Ocean. The notothenioids underwent rapid adaptive radiation after the onset of oceanic cooling in the Southern Ocean which resulted it the seas around Antarctica becoming thermally isolated from connecting oceans. Part of this adaptive radiation is linked to the pelagisation and extending ecological niches into the water column. Understanding the ecological and environmental drivers of interannual and long-term variability in life history and population dynamics of notothenioids is important for conservation and management decisions in the Southern Ocean.

The sub-Antarctic island of South Georgia is a hotspot of regional marine biodiversity in the Southern Ocean and supports high levels of endemic and range-edge fauna. It is also one of the fastest warming areas in the Southern Ocean. This means that many species may find toleration and adaptation to higher temperatures difficult. In addition, it is an important fishing region in the Southern Ocean. The management of the fisheries is conducted by the Government of South Georgia and the South Sandwich Islands (GSGSSI) under the auspices of CCAMLR. This means GSGSSI are managing fisheries whilst mitigating against longer-term changes in climate. A key component of the fish fauna around South Georgia are the family Channichthyidae, also known as icefishes. Icefish are unique amongst vertebrates, in lacking the blood pigment haemoglobin, an adaption that may make them particularly susceptible to future warming. Icefish also exhibit unusual reproductive behaviours with some species known to show nesting behaviours. There are three species of closely related icefish Champsocephalus gunneri (mackeral icefish), Chaenocephalus aceratus and Pseudochaenichthys georgianus), which make up a substantial proportion of the fish biomass on the continental shelves of South Georgia and Shag Rocks and have undergone niche differentiation for successful coexistence. Champsocephalus gunneri is a commercial fisheries target while management measures are in place for the other two species. However, there are still important gaps in our knowledge of key life history processes, especially related to reproductive cycles and behaviour, and ecological and environmental drives of spatio-temporal variability in biomass and life history stages within these species.

The main objectives of this project are to quantify key life history processes, demographic properties and resource partitioning in the icefishes C. gunnari, C. aceratus and P. georgianus on the South Georgia and Shag Rocks continental shelves. Given the differences in ecological niches for these species, it is expected that they will respond differently to fluctuating environmental conditions. At present, there are management measures in place which limit the total biomass caught as target or by-catch in the commercial fisheries, but further information is required at the regional scale to help inform the spatial management and maintain viable populations to help mitigate against future warming. Key questions which need to be addressed include:
1) identify potential spawning locations, timings and nursery grounds and assess whether these are linked to environmental or bathymetric features;
2) assess the environmental drivers of interannual variability in recruitment, hatching times and growth rates of larvae;
3) assess the distribution of life history stages around the island and how they vary between and within years;
4) quantify resource partitioning among life history stages of the different species.

The research will feed into GSGSSI’s management of the fisheries and into wider international policies implemented through CCAMLR. A key goal of GSGSSI is to ensure long-term sustainability within their maritime zone by implementing an ecosystem-based approach to management. Fisheries revenue accounts for over 70% of GSGSSI income of which the mackerel icefish fisheries provides an important contribution. These funds help GSGSSI with the environmental management of the islands within their maritime zone and meeting important international obligations for the conservation of higher predators (e.g. birds and whales). The results are expected to contribute towards the developing further enhancement of the GSGSSI’s marine protected areas.

Methodology

The student will undertake a combination of laboratory-based analyses, environmental and habitat mapping and statistical modelling of large datasets. The project will use data collected from the trawl surveys around South Georgia and Shag Rocks over the last 30 years and larval fish collections from the last 20 years from King Edward Point. Video footage of the South Georgia and Shag Rocks continental shelves will be examined for evidence of icefish nesting sites. The PhD will use archived frozen material and potentially new samples from the groundfish surveys. There may be an opportunity to participate in the groundfish survey but this cannot be confirmed at this point. Habitat mapping, spatial, temporal and spatiotemporal analysis of biological and environment data will be undertaken. Appropriate statistical models will be developed depending on the research questions. Hierarchical models will be explored given the nature and scale of temporal and spatial data. Laboratory based work will be done using previous collected samples and will potentially include aging using sagittal otoliths, histology of reproductive organs and examine resource partitioning using stomach content and stable isotope analyses . This will be dependent on the research direction the student takes.

Project Timeline

Year 1

• Conduct comprehensive literature review on fish life history strategies with particular emphasis on Southern Ocean species.
• Familiarisation, data extraction and analyses of key life history information from the South Georgia fisheries database.
• Examination of video footage from the South Georgia shelf.
• Potential fieldwork

Year 2

• Spatiotemporal analysis of icefish species using data from the groundfish survey database.
• Life history studies into aging, maturity, hatching times and potentially reproduction.
• Present findings at UK conference.
• Prepare first manuscript.

Year 3

• Stomach content and stable isotope analysis to examine resource partitioning.
• Temporal analysis of larval fish data.
• Present findings at international conference.
• Prepare second manuscript.

Year 3.5

• Synthesis and habitat and environmental mapping of key life history stages around the continental shelves of South Georgia and the Shag Rocks.
• Preparation of policy papers for CCAMLR.
• Prepare third manuscript.
• Thesis completion

Training
& Skills

The student will receive training in fisheries related data collection, fisheries laboratory analyses (e.g. aging techniques using sagittal otoliths), biochemical techniques, running an isotope ratio mass spectrometer and analysing data resulting in the following skills (i) database structure and interrogation; (ii) preparation of tissue samples for stable isotope analysis; (iii) species identification for stomach content analysis; (iv) summarising and manipulating large data sets; (v) statistical analyses of large data sets; (vi) preparation and presentation of results at national and international conferences; and (vii) production of scientific and policy related papers. The training above is not prescriptive and there may be other technical and personal development training opportunities offered by the DTP and Newcastle University (e.g. scientific paper writing). There will be opportunities to present at national and international conferences, which will form an important aspect of the student training. The student will benefit from working in tandem with research teams focusing on the marine environment, statistical modelling, and synthesising evidence for policy decisions at Newcastle University and BAS. A key element of the training will be taking ecological data, either historical or new, right through to scientific and policy related outputs.

References & further reading

South Georgia and South Sandwich Islands MPA Research and Monitoring Plan: https://www.gov.gs/docsarchive/Environment/Marine%20Protected%20Area/SGSSI%20MPA%20Research%20and%20Monitoring%20Plan%202021.pdf
Morley SA et al. (2014) Geographical isolation and physiological mechanisms underpinning distributions at the range limit hotspot of South Georgia. Rev Fish Biol Fisheries 24: 485-492.
McCormack SA et al. (2019) Using stable isotope data to advance marine food web modelling. Rev Fish Biol Fisheries 29: 277-296.
Hogg O et al. (2016) Landscape mapping at sub-Antarctic South Georgia provides a protocol for underpinning large-scale marine protected areas. Scientific Reports 6: 33163
La Mesa M et al (2020) Parental care and reproductive strategies in notothenioid fishes. Fish and Fisheries 22: 356-376.

Further Information

For further information, please contact Dr William Reid (william.reid@newcastle.ac.uk) and Dr Philip Hollyman (phyman@bas.ac.uk). Students are encouraged to contact Dr Reid and Dr Hollyman to discuss the PhD before application.

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