Oyster reintroduction on the Humber Estuary

Native oysters bagged and on trestles in the Humber - picture Amy Pickford

Amy Pickford, one of our Living Seas Volunteers in 2019, has moved on to new pastures. Here she gives a summary of the native oyster reintroduction work she's been doing with our colleagues in the Yorkshire Wildlife Trust.

A little bit about me

I graduated in 2018 with a BSc in Environmental Conservation from Bangor University. I continued to live in Bangor for another year in order to gain some experience in my field. I volunteered with a few organisations in the area, amongst them the North Wales Wildlife Trust. Due to my course only offering one marine based module, I decided to devote my time with the trust participating in task days for the Living Seas Project to improve my marine knowledge.

when the opportunity arose to help establish an aquaculture site for native oysters on the Humber Estuary, I couldn’t resist joining the team.

As of the beginning of October this year I started a year-long placement with the Yorkshire Wildlife Trust (YWT) as a Tomorrow’s Natural Leader (TNL). Our time is split between the office HQ in York, and training and task days on various nature reserves in Yorkshire. Most of the training and task days are land-based so when the opportunity arose to help establish an aquaculture site for native oysters on the Humber Estuary, I couldn’t resist joining the team.

 

The Humber Aquaculture Partnership (HAP)

The Humber Aquaculture Partnership is a two-year project run by the University of Hull and the YWT, funded by the European Maritime and Fisheries Fund (EMFF). The project is located on the Humber Estuary at Spurn Point with the aim of developing a multi-species aquaculture site including mussels, razor clams, seaweed and native oysters.

Oysters are known as a keystone species because the structures they form encourage other fish and plant life to the reef.

The population of native oysters sadly died out in the 1950s due to pollution and overfishing. Oysters are known as a keystone species because the structures they form encourage other fish and plant life to the reef. The reintroduction hopes to improve water quality and encourage marine life. To monitor this, several research themes will be developed investigating the impact of sustainable aquaculture on the surrounding species richness and biodiversity as well as growth, survival and the reproductive potential of the cultured species throughout the project.

A trial in April proved that 1,500 adult oysters transported from Loch Ryan showed the potential to survive at Spurn Point and helped to reveal the best place to establish the site, which is 3.5 miles out to sea in a sheltered area near the former bathing beach and carpark.

Task Days

The team included Project Officer Daniel Cowing of the Biological and Marine science department and Dr Magnus Johnson of the Environmental Marine Science department at the University of Hull, as well as other TNLs and some students from the university who will be conducting research projects once the site has developed.

Here I describe my involvement over the course of a month helping with many aspects of work required in setting up this project.

Day 1 (Monday 28th October 09:00-16:00):

Arrive at the discovery centre for 09:00-09:30 for transport by Unimog (Multi-purpose all-wheel drive truck - specialised for sandy terrain) to the point.

  • Trestles arrived transported by a tractor and trailer across the beach to hard standing. The main aim of the oysters is for them to clean the water of the Humber. The trestles act as an artificial base to allow appropriate nutrient and water flow.
  • Carried 40 trestles (5 rows of 8) by hand from hard standing to the site
  • Moved oyster bags from trestles 2 & 3 to holding trestles for analysis - check oyster survival/size on trestles 2 & 3. The oysters would usually attach themselves to natural surfaces. In order to collect data they are put into the bags to avoid loss of stock and ease the distribution of the population as the researchers see fit.
  • Walked back up from the site to the YWT garage to make and store more oyster bags for tomorrow

Day 2 (Tuesday 29th October 09:00-16:30):

  • Meet at discovery centre at 09:30, load equipment (rubber straps, gloves, dry-suits, push nets) onto Unimog and transport to site
  • Ready-made oyster bags transported down to the site using the ATV whilst the rest of the group walked over.
  • Group was split into groups and assembled five bags per trestle using rubber ties (2 ties on each side).
  • The oysters were not available that day (due to local supply issues).

Day 3 (Wednesday 30th October 10:30-16:00):

  • Oysters (1,200) arrived around 12pm and were transported in an IBC (Intermediate Bulk Container) to the YWT garage.
  • Oysters were prepared by bathing them in a container of freshwater containing a small amount of bleach. Then transferred to a container only containing freshwater to be rinsed. This process is to ensure they are free of any Invasive Non-Native Species (INNS). Then placed into baskets and loaded onto the ATV to take back to the garage.
  • Here the oysters were distributed into bags according to stock densities (40,30,20,15).
  • Bags were then taken down onto site and secured onto trestles using rubber ties.

Day 4 (Wednesday 27th November 9:30-15:00):

  • Oysters (900) arrived around 12:30pm and were prepared for bagging.
  • Due to the tide coming in we put all the bagged oysters at the middle site overnight ready to be moved to the main site the next day.

Day 5 (Thursday 28th November 10:30-14:30):

  • Before redistributing the oysters, we took photos for measurement reference to compare against the oysters that arrived earlier in April.
  • We had 29 bags holding 30 oysters in each, and 2 bags held 15 each.
  • Bags we secured onto trestles at main site using rubber ties.

 

Amy Pickford,Tomorrows Natural Leader, Yorkshire Wildlife Trust