CLIMATE CHANGE AND FISHING EFFECTS ON DEMERSAL FISH
MBA sampling of the demersal fish assemblage in the English Channel near Plymouth started in 1911. This work 97-year time series has continued with recent sampling of station L4 as part of the ‘Standard Haul’ time series using the RV Plymouth Quest, and repeat surveys of inshore sites (Bigbury Bay and Whitsand Bay) using MBA Sepia. Analyses of both of these datasets reveal declines in the abundance and body size of larger demersal species, such as rays, angel shark, and some large flatfish. The demersal component of the catch is now dominated by small, typically non-commercial ‘southern’ species from low trophic levels, and these species have shown changes in abundance that has ‘tracked’ climate change-related changes in sea surface temperature.
We also have a NERC-Defra-funded project exploring patterns of long-term change in UK demersal fish assemblages over broader spatial scales. This project uses trawl survey data collected from the fisheries laboratories in the UK and Ireland. With colleagues from Cefas Lowestoft, FRS Marine Laboratory Aberdeen, AFBI Belfast, and the Marine Institue Galway, datasets have been compiled spanning the last 50 years. These data will help to predict the consequences of future climate change and fisheries management strategies.
With colleagues we are also investigating how thermal changes have influenced the timing of life history events in the English Channel marine fish assemblage. Because most marine teleosts have a planktonic larval dispersal phase during their early larval life-history, the timing of appearance in the plankton is indicative of the timing of the reproduction. The MBA has been monitoring the composition of the ichthyoplankton for nearly 100 years, but the most temporally high-resolution dataset was collated by Professor Alan Southward between 1975 and 1988. Using these data we have been able to analyse the timing of the appearance of the spring and summer spawning assemblages, and are exploring the mechanisms that drive these changes.
People involved: Dr Martin Genner (MBA & University of Bristol), Professor David Sims (MBA), Matthew McHugh, Peter Rendle , Dr Victoria Wearmouth, Dr Nick Halliday (MBA), Dr Stephen Simpson (University of Bristol), Professor Stephen Hawkins (MBA & Bangor University).
Funding: NERC Oceans 2025 (Themes 6 & 10), NERC-Defra Sustainable Marine Bioresources initiative.
CLIMATE EFFECTS ON REGIONAL COD POPULATIONS
This project aims to identify potential mechanisms underlying observed changes in relative abundance of young cod off southwest Britain (western English Channel, Celtic Sea and Bristol Channel). Long-term monitoring of demersal fish species from the MBA ‘Standard Haul’ trawl series (1911–2007) has been complemented by recruitment estimates and effort-corrected landings data, together with analysis of the Continuous Plankton Recorder dataset in these regions to better understand climate-linked bottom-up effects of zooplankton on demersal fish stocks. We have explored some apparently counter-intuitive trends observed in northerly distributed cod over the last century. It is apparent that climate may be affecting indirectly the survival of early life stages of fish, which in turn may influence levels of recruitment.
People involved: Professor David Sims (MBA), Dr Gregory Beaugrand (CNRS Wimereux, France), Dr Martin Genner (MBA & University of Bristol), Dr Peter Henderson (Pisces Conservation Ltd), Professor Stephen Hawkins (MBA & Bangor University).
Funding: NERC Oceans 2025 (Themes 6 & 10). |
