Searching our Shores: Hill Head 2019

Our shore searching season continues with an intertidal survey at Hill Head in glorious sunshine.

Conditions were perfect for our intertidal survey at Hill Head - sunny, warm, and no wind. It was a pleasure to be on the beach! An impressive flock of 18 swans flew overhead while we were there, but our friends at Bird Aware Solent would be pleased to hear that we managed not to disturb any birds.

As part of our surveys we divide each beach into zones according to the presence of certain species or features. We usually do this by laying down a tape measure from the top of the beach to the water line, but the beach at Hill Head is bit more complicated. It's essentially flat but has mounds and channels, so for our zones we used a wooden groyne at the start, muddy sand with brown seaweed, a winkle dominated band with a mussel bed and red seaweeds, and ground exposed only briefly at the low water’s edge. We tried to map all this and, unlike at Calshot, these features seem to be in roughly the same locations as in previous years.

At the top of the beach we found a great number of the seaweeds known as ‘wracks’, which are mostly members of the genus Fucus. These are all intertidal brown seaweeds with a strong midrib and can be difficult to identify, not least because they can hybridise with each other. But they're such a common sight on our beaches that they're worth spending time with.

If you're not into seaweeds just note them down as ‘Fucus sp.’ and don’t worry about the species – looking for brittle stars, crabs, and sea squirts under stones is just as valuable! But for anyone who is interested the Seasearch guide, Seaweeds of Britain and Ireland (highly recommended) revealed the following clues:

  • Bladder wrack (Fucus vesiculosus) has multiple main axes (an axis being a bit like a stem) with air bladders that usually appear in pairs, and tends to grow larger than the other wrack species. We didn’t find any this time.
  • Fucus guiryi (no common name) has a single main axis and fruiting bodies that have a flat rim (like ravioli). We found some on the groyne.
  • Horned wrack (Fucus ceranoides) branches out into fan-like shapes tipped with pointed fruiting bodies that can have long air pockets. We found some on the sand.
  • Serrated or toothed wrack (Fucus serratus) has wide, flat fronds with serrated edges. We didn’t find any this time.
  • Spiral wrack (Fucus spiralis) has multiple main axes that are often twisted and can have swellings along the edges. We found some on the groyne.
Fucus guiryi seaweed © Jenny Mallinson

Fucus guiryi seaweed © Jenny Mallinson

Telling the difference between rough periwinkles (Littorina saxatilis) and edible or common periwinkles (Littorina littorea) is also tricky unless you find ones with clear features. Try holding your specimen with the pointed end upwards and looking at the opening: on the rough periwinkle the top of the hole is more like a right-angle, while on the edible winkle the angle tends to slope up towards the point. Rough periwinkles are also usually found higher up the beach and have rings around them, but bear in mind you can also find these rings on juvenile edible winkles. 

It was good to find more than one native or European flat oyster (Ostrea edulis), though there were plenty of Pacific oysters (Crassostrea gigas). The three native oysters we found were gnarled old 10-12 cm ones; more than a match for the hordes of egg-laying tingles (Ocenebra erinacea, also known as the sting winkle or oyster drill) that eat them. But the juvenile 4 cm one that Ken found would be easy prey - this may be one reason why they're so scarce now, although it is exciting to see they're still breeding.

Lifting up some shells we found Lepidochitona cinerea - sometimes called the ‘shore chiton’ in these parts since it's the most frequently found chiton on our beaches. We also saw both of the tufted or bristled chiton species found in our area: Acanthochitona fascicularis and Acanthochitona crinita (no common names). Look for differences in their mantles and surfaces to make telling them apart easier. We were careful to replace any stones we moved or turned over during the survey – please remember to do the same as many species will be living beneath them!

The mystery of which species created the worm casts we saw was solved by a convenient bait-digger at the top of the beach, who was finding lugworms (Arenicola marina). Sadly this digger was not back-filling his holes – if you dig for bait please do this, as it helps minimise damage to the habitat. We also only saw one sea slug on this survey: the same little white one (Acanthodoris pilosa) that we found at Calshot, this time found by Laura.

Laura with acanthodoris pilosa sea slug © Jenny Mallinson

Laura with sea slug (Acanthodoris pilosa) © Jenny Mallinson

Once again, many thanks to the 24 eagle-eyed spotters who attended the survey. We've added our findings to the species list for this site – if you're interested in seeing this, need help with identifying your own finds, or have anything to add (we will credit you, please send a photo if possible) then do get in touch.