Chichester Harbour Small Fish Surveys 2016

Introduction

 Chichester Harbour is a natural harbour on the border of Hampshire and West Sussex, on the south coast of England.  It is about 3700 hectares, mainly salt marsh, intertidal mud and sand, and subtidal mixed mud and shell.  It has numerous conservation designations: Special Area of Conservation, Special Protection Area, Ramsar site, Site of Special Scientific Importance, Area of Outstanding Natural Beauty.  Sussex IFCA conducted a biannual small fish survey in Chichester Harbour between 2010 and 2014.  The surveys were conducted in partnership with Chichester Harbour Conservancy, with their vessels and staff used to access the survey sites. In addition, in 2016, 19 people from 9 organisations supported the surveys.  During 5 years of surveys, over 25,000 fish have been found, comprised of 48 species.

Survey sites o Site Month Water temperature ( C) Salinity (PSU) PSU = practical salinity units July 19.8 34.5 Pilsey 0 = fresh water September 20.7 34.7 35 = seawater June 19.2 30.8 Copperas September 20.8 33.2 June 20.8 33.9 Winner September 20.4 34.4

Pilsey Copperas

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Winner

Survey equipment

2m survey beam trawl 43m seine net

Multiparameter meter

Sampling

Date Site Wind & weather Tide 21st June Copperas SE force 1, overcast High 13:30 28th June Winner SSW force 3 Low 11:35

27th July (postponed from June Pilsey SW force 4 Low 11:00 due to unsuitable weather) 1st September Copperas SW force 2, sunny High 12:30 13th September Pilsey SE force 3-4, sunny Low 15:15 14th September Winner SE force 3, sunny Low 16:00

Results

In total, there were 1983 fish of 25 species. Bass (Dicentrarchus labrax) and sand smelt (Atherina presbyter) were jointly the most abundant (30.6% n=607), followed by common goby (Pomatoschistus microps) (18.5%) and sprat (Sprattus sprattus) (10.4%). These four species made up 90% of the total abundance.

Relative abundance

0% 5% 10% 15% 20% 25% 30% 35%

Bass Sand smelt Goby - Common Sprat Goby - Sand Goby - Painted Mullet - golden grey Wrasse - Ballan Bass Herring Wrasse - Corkwing Bream - Black Dragonet - Reticulated Goby - Black Goby - Juvenile Sand smelt Goby - Two spot Species Blenny - Shanny Goby - Rock Pipefish - Greater Pipefish - Lesser Sole - Dover Brill Pipefish - Snake Pipefish - Worm Sole Common goby Rockling - five bearded Sea Scorpion - Long-spined

Seasonality

In June/July, there were 497 fish of 17 species. In September, there was much greater abundance (1486) and more species (20).

The June/July abundance was well below the 2010-2014 average of 1560 (32%). This may have been due to an unusually wet and warm winter. In June, there was also above average rainfall (MetOffice), although the salinity readings were similar to previous years.

Site variation

Pilsey had the most number of species (22) and Winner had the least (11). Winner also had the lowest abundance (113) and Copperas had the highest (1034).

Winner was the only place where Dover sole and brill were found. The most abundant species at this site was sand goby which made up 82% of the total abundance at Winner.

There were three main species at Copperas: bass (42% of total abundance at Copperas), common goby (35%) and sand smelt (22%). 71% of the Harbour’s bass and 99% of the common gobies were found at Copperas.

Pilsey had 11 species that were not found at the other sites, including three species of goby, three species of pipefish and two species of wrasse. Ballan wrasse

Comparison to previous years

There have been three species found this year that have not been previously found on this survey: brill (Scophthalmus rhombus), worm pipefish (Nerophis lumbriciformis) and five bearded rockling (Ciliata mustela).

This year, there was lower abundance; 2/3 of the average abundance Brill 2010-2014. There were 1983 fish compared to the 2010-2014 annual average of 3033.

Some species in particular, had much lower abundance than the 2010-2014 average: bass 54%, sprat 46%, golden grey mullet (Liza aurata) 6% and herring (Clupea harengus) just 1%.

Other species had a greater abundance compared to the 2010-2014 average: sand smelt were 36% more abundant and there were more blennies, pipefish and dragonettes.

Non-fish species

There was a variety of conspicuous non-fish species including juvenile cuttlefish, shore crabs, sea spiders, hermit crabs, squat lobsters, sea squirts, sponges, amphipods, molluscs, bryozoans, hydroids and a diversity of algae.

Squat lobster Diversity

The Simpson’s Index of Diversity was used to assess the number of species and the evenness of distribution of abundance across those species at each site. The index is a scale of 0 to 1, where 0 represents no diversity and 1 indicates infinite diversity.

The average index of diversity was 0.715. This was higher than in 2014 (0.553) and 2013 (0.428), as these years were heavily dominated by herring, common goby and bass.

The index of diversity was very slightly higher in spring (0.717) than autumn (0.712).

Site specific diversity was lower than the index for the whole Harbour. Pilsey had the highest index of diversity (0.595) and Winner had the lowest index of diversity (0.340).

Copperas had the greatest difference in between spring (0.270) and autumn (0.655).

Bass

Bass are an important species for commercial and recreational fisheries. Chichester Harbour is a Bass Nursery Area. There are concerns about current stock levels. Male bass mature at 31-35cm 4-7 years old and female bass mature at 40-45cm 5-8 years old.

In the 2016 fish survey, 85% of bass were caught in the autumn.

Bass less than 90mm long were considered group 0 age class, spawned in early 2016. 91% of bass were group 0 and 93% of these were found in the autumn.

Bass 90 – 140mm long were considered group 1 age class, spawned in early 2015. 6% of bass were group 1 and all of these were found in the spring.

25%

20% Autumn Spring

15%

10% Relative abundnace Relative

5%

0%

Length (mm)

Sand Smelt

Sand smelt were the most abundant species jointly with bass.

They are a shoaling fish, often found in inshore areas. They are not caught commercially but may be an important food source for birds such as terns. They can reach a maximum length of 150-200mm.

The majority of the sand smelt caught in the fish surveys were between 45mm and 85mm. The sand smelt caught in the spring were generally smaller than those caught in the autumn.

10% 9% 8% 7% 6% 5% Autumn 4% Spring

3% Relative abundance Relative 2% 1% 0% 40 50 60 70 80 90 100 110 120 Length (mm)

Common goby

Common goby was the third most abundant species, after bass and sand smelt.

Gobies are small, bottom dwelling fish. They are not caught commercially but are an important food source for larger fish.

The common gobies caught on the fish survey were between 23mm and 60mm.

Common gobies between 23mm and 48mm were found in both the spring and autumn but fish larger than 49mm were only found in the spring.

20% 18% 16% 14% 12% Autumn 10% Spring 8%

6% Relative abundance Relative 4% 2% 0% 20 25 30 35 40 45 50 55 60 Length (mm) Comparison to other sites

Sussex IFCA also conducts small fish surveys in Medmerry managed realignment (near Selsey) and Rye (East Sussex) using a combination of seine nets, fyke nets and beam trawling. Direct comparison of these surveys is difficult due to the different methods, sites and habitats. However, it can still be useful to put the Chichester Harbour survey in context. In 2016, there were 18 species in Medmerry and 27 in Rye. The average index of diversity was 0.651 in Medmerry and 0.827 in Rye. In comparison, Chichester Harbour had 25 species, and the average diversity was 0.715.

Collaboration and funding

Sussex IFCA conducted the fish survey in collaboration with Chichester Harbour Conservancy and with the support of the Environment Agency, Natural England, the Marine Management Organisation, RSPB, University of Brighton, University of Sussex and St Philip Howards Catholic High School.

Support funding was provided by the Natural Environment Group. Chichester Harbour Conservancy received 80% as a contribution to the cost of fuel for their vessels. Sussex IFCA used the remainder to maintain and upgrade their survey equipment. All other costs were covered by the organisations involved.

Sussex IFCA would like to sincerely thank the Natural Environment Group for their support. We are grateful for their contribution to the continuation of this important survey which furthers understanding of the fish populations in this sensitive area.

The Natural Environment Group is a subsidiary group of the Solent European Marine Site Management Group. Natural England chair the group and the Solent Forum provide the secretariat. The aim is to coordinate the implementation of nature conservation actions across the Solent.

Conclusions

 There were 1983 fish of 25 species.  Bass and sand smelt were jointly the most abundant, followed by common goby and sprat.  There was nearly three times the abundance in the autumn compared to the spring.  The total abundance for the year was 2/3 of the 2010-2014 average abundance.  The average Simpson’s index of diversity was 0.715, higher than in 2013 or 2014.  85% of bass were caught in the autumn and 91% of bass were group 0, spawned in early 2016.  The surveys were a fantastic collaboration involving 19 people from 9 organisations.