The destruction of aquatic ecosystems is a major issue facing conservationists globally – causes include microplastic pollution, acidification, global warming and over-fishing. The manufacturing team at NHBS have produced a series of new survey nets designed to help researchers gather data on microplastics and to sample plankton more efficiently. This blog describes the sea trials performed using our prototype nets to establish the optimal towing speeds and sea conditions as well as whether the nets worked effectively and were robust enough to withstand exposure to the marine environment.
Three new nets were tested – the Manta Trawl Net, which is designed to sample microplastics in calmer inshore waters and on rivers and lakes. The Avani Trawl Net, which is designed to sample microplastics in rougher, offshore environments and the Bongo Net (a pair of 300mm plankton nets joined in the middle and weighted with a depressor vane) which is designed to allow researchers to use two different mesh nets during a single trawl. Plymouth Sound was an ideal location, as we had both inshore and offshore designs to test and the breakwater provided us with easy access to both sheltered water and the open ocean.
The first design tested was the Bongo Net. The net performed very well. The sampling depth was easily adjusted by modulating the speed of the boat and the depressor vane kept the net level in the water. In our tests the Bongo Net performed best at towing speeds of between two and four knots.
Bongo Net
Next, we tested our inshore Manta Trawl Net. The Manta Trawl Net is designed for microplastics sampling in calm inshore waters and on rivers and lakes. The Manta Trawl Net has a post box shaped aperture and twin ‘wings’ (manta wings) mounted onto the frame which serve to lift the net frame so that samples are efficiently collected at the top of the water column. This net was tested at a variety of towing speeds and performed best at speeds of between two and four knots.
Manta Trawl Net
The last net to be tested was The Avani Trawl Net. The Avani Trawl Net is designed for offshore microplastics sampling. The vertical orientation of the aperture of the net ensures that samples are collected from the top few centimetres of the water’s surface in slight to moderate swell conditions. To test this net, we ventured out beyond the breakwater where the swell was approximately 1-2m. The net stood upright and performed as expected at speeds of between four and eight knots when exposed to smaller waves of approximately one metre in height. When approaching larger waves, we found that the net had a slight tendency to cut into the side of the wave at speeds of between six and eight knots and that the net performed best at slightly lower speeds.
Avani Trawl Net
All of the nets functioned properly, and our haul included both microplastics and icthyoplankton (fish eggs and larvae). Both the frames and the nets also withstood the sea conditions well and we could find no faults with their design or build – all told a successful trial.
If you are interested in these nets look out for them in our 2019 catalogue, find them on nhbs.com, or contact us on customer.services@nhbs.com and we will send you more information as soon as it becomes available.
These bespoke nets, made by NHBS, are being used by ZSL in an ongoing project to monitor juvenile and larval fish populations in the Thames.
The Ichthyoplankton Net
Earlier this year we were contacted by the Zoological Society of London (ZSL) who were interested in working with us to make a bespoke aquatic survey net.
Their specifications required the net to have a square frame with a four point bridle and connections for a flow meter. It also needed to have a diving vane which would ensure that it could be towed stably at a set depth, and a screw on cod end with a bag made from 53µm and 250µm mesh. Following these guidelines, our engineer and seamstress got to work and within a couple of weeks a detailed specification was agreed. The nets were then manufactured and two were sent to ZSL in February.
First draft of the net design
Several months later we were delighted to receive some photos from Anna Cucknell, who manages ZSL’s work on fish conservation in the Thames, showing the nets in use.
“It was great to work with NHBS, who listened to our specific needs to design bespoke sampling nets for juvenile fish, and used their experience to adapt our designs to fit our needs. Our juvenile fish surveys on the Thames are the first of their kind, in scale and resolution and we hope the results from which will be applicable in the Thames and further afield to help drive conservation and better management of our estuaries for all fish species”. Anna Cucknell, Thames Project Manager, Zoological Society of London
Nets are towed both at the surface and at a depth of two metres. Combined with data from seine and intertidal nets, these surveys provide a comprehensive picture of larval and juvenile fish populations.
Fish Conservation in the Thames
The nets we made for ZSL are being used for an ongoing project to monitor the use of the Thames by juvenile fish.
The Tidal Thames is home to more than 100 fish species including many that are commercially important such as Dover sole and European seabass. It also provides critically important habitat for rarer species, including European smelt and European eel.
Like most estuaries, the Thames provides invaluable spawning, migratory and nursery grounds but, despite this, the region is poorly studied. The ZSL project hopes to remedy this by providing essential information about the health of fish populations in the estuary, and to assess how these are affected by water quality and local developments.
Boat-based sampling for juvenile fish
The project, funded by Tideway, involves both boat-based and foreshore sampling and, excitingly, also provides an opportunity for volunteers to get involved via its citizen science scheme. Volunteers can help with a variety of tasks including measuring, identifying and counting the fish.
For more information about the Tidal Thames fish conservation project, head over to the ZSL website.
Interested in getting involved? Sign up here to volunteer.
Have a bespoke project in mind? Contact our Wildlife Equipment Specialist team on 01803 865913 or via email at customer.services@nhbs.com.
Public sighting records are important for UK cetacean conservation. Atlantic Bottlenose Dolphins by Jo Garbutt is licenced under CC BY 2.0
Catching a glimpse of a whale or dolphin whilst visiting the coast is a uniquely memorable experience and a few hours spent whale and dolphin watching is fun for all age groups. Plus, your sightings can really make a difference and will add to the growing body of survey data collected for the UK coastline.
Keep reading for some tips on when and where to watch whales and dolphins, how to get started and where to report your sightings.
When and where should I watch cetaceans and what am I likely to see?
The best time for spotting cetaceans is between April and October when visitors to our coastal waters are at their highest. Some areas are undoubtedly better than others for catching a glimpse of these elusive animals: Devon, Cornwall and Cardigan Bay in Wales are good places to go, as well as the coasts of northern Scotland.
Twenty-nine species of cetacean have been recorded in UK waters, and some areas of our coastline are home to permanent populations of dolphins. The most commonly reported species are bottlenose dolphins, harbour porpoises and minke whales, although rarer visitors have included killer whales, humpback whales and striped dolphins.
Of course, cetaceans aren’t the only things you will see. Keep your eyes peeled for seals too and enjoy the seabirds and beautiful views at the same time!
How do I get started watching whales and dolphins?
For most people, watching cetaceans from the land (rather than from a boat) will be the most convenient and economical option. Any place where you can sit comfortably with a good view of the sea will suffice, but if you can make your way to a cliff top then this will provide a better vantage point. Calm, overcast days tend to be the best for spotting cetaceans as the combination of swell, choppy waves and surface reflections can make fins all but impossible to see. For the same reason, the hours following dusk and prior to dawn are the best times of day to go.
A watch is conducted by scanning the surface of the water with the naked eye, switching to binoculars periodically or whenever you notice a disturbance at the surface. As soon as you see something that may be a whale or dolphin, concentrate your binoculars in that area, making sure to scan a little way around in case it surfaces again nearby. Another good technique is to look out for seabirds circling or diving as this may indicate cetaceans feeding just below the surface.
Any binoculars (or a scope and tripod) can be used for sea watches. If you are looking for binoculars specifically for this activity, however, make sure to go with a model that has a large objective lens diameter as this will improve the light transmission and will help with viewing in lower light conditions.
For researchers studying marine mammals, items such as thermal imaging scopes and hydrophones are useful additions to the surveying toolbox and will allow them to find and identify cetaceans in a greater range of conditions as well as enabling more detailed investigation of behaviour.
Where do I submit my sightings?
Several organisations in the UK offer online sighting forms where you can submit information about whales, dolphins and porpoises that you have confidently identified during your watch. Take a look at the Sea Watch Foundation, the Whale and Dolphin Conservation, or the Cetacean Research & Rescue Unit websites for sighting forms. Other regional groups such as the Hebridean Whale and Dolphin Trust and Norfolk Cetaceans also collect local sightings so it might be worth finding out if there is an active recording group near to where you live.
Check out the NHBS website for a great range of binoculars and scopes, as well as other handy field kit such as waterproof clipboards and notebooks. Also have a look at these two field guides to help with identifying whales and dolphins.
Guide to the UK Cetaceans and Seals
Whales, Dolphins and Seals: A Field Guide to the Marine Mammals of the World
