Report compiled by Louise MacCallum

Transcription

1 2014 Report compiled by Louise MacCallum

2 Contents 1.0 Introduction..Page Methodology...Page Results...Page Key Findings...Page Metadata...Page Langstone and Chichester Comparison.....Page Species caught in Langstone Harbour...Page GPS Imagery...Page Discussion...Page Future Improvements..Page Bibliography...Page 16 L-R: processing the catch, Ballan Wrasse, recovering the trawl Acknowledgements Thanks to the following people for providing assistance and advice with the 2014 Langstone Harbour Small Fish Survey: Jim Clark, Patrick Cooper, Lowri Evans, Paul Farrell, Vicki Gravestock, Pete Hill, Loren Hiller, David Mayne, Jon Meek, Kat Nelson, Nick Rogers, Wez Smith, Dawn Thompson and Lewis Yates. 2

3 1.0 Introduction 2014 marked the third consecutive year of the Langstone Harbour Small Fish Survey. The survey was once again conducted in partnership between the Langstone Harbour Board (LHB), the University of Portsmouth (UoP), the Southern Inshore Fisheries and Conservation Authority (sifca). During 2014 the partnership also welcomed the Royal Society for the Protection of Birds (RSPB). The Langstone Harbour Small Fish Survey aims to create an increased understanding of Langstone Harbour s fish community over time by building a long term data set detailing fish community composition. As in previous years, three sites in the harbour were surveyed using two catch methods in both June and September. Fish caught were all identified, measured and counted. Environmental data including water temperature and salinity were also recorded at each site. Site 1 Bedhampton Wharf The sediment at this site is comprised of mud and gravel. The site is adjacent to Hermitage Stream the main input of freshwater into the harbour. Site 2 Sword Sands Golden sandbank entirely covered during high water. Over 1000m from the harbour shoreline. Site 3 Eastney Point The sediment here is composed of course gravels. Tidal flows regularly exceed 5 knots at this site. The site is adjacent to a piled pontoon. Changes at sites since 2013 Survey Shortly prior to the September survey, a maintenance dredge took place at Bedhampton Wharf. A large section of the beach from which the seine net is deployed at this site was removed during the dredge. Additionally, the approach channel along which the beam trawl is towed had a layer of loose silt at the bottom deriving from dredging activity. The other sites remained largely unchanged from 2013, although during beam trawling a number of obstructions were encountered suggesting the arrival of unidentified objects in the trawl paths. 3

4 2.0 Methodology Hauling the seine net at Bedhampton Wharf Methodology used during 2014 was the same as that used during previous survey seasons. At each site a seine net and beam trawl were used as catch methods. All fish caught during the survey were identified, measured and returned to the sea (with the exception of a small number of individuals which were retained by UoP for further analysis). Metadata including water temperature and clarity were also recorded at each site. Full details of the survey methodology can be found in the Langstone Harbour Small Fish Survey Standard Operating Procedure document which should be read in conjunction with this report. A few small adjustments were made to the methodology following experience gained during the 2013 season. These adjustments are summarised as follows: 1. Seine net deployment was undertaken from the RSPB vessel Good Tern. This 15 4 aluminium work boat has a 6 inch draught and is powered by a 25hp outboard engine. 2. A yellow pick up buoy was attached to the beam trawl with a 10m rope. This allowed the positon of the trawl to be monitored whilst being towed, as well as providing an alternative recovery option for the trawl. 3. The digital thermometer was replaced with a Brannan spirit filled glass thermometer. 4. The order in which the catch methods were deployed at each site varied in response to on site variables such as the presence of other vessels in the vicinity of the site. Setting the seine net from the Good Tern 4

5 3.0 Results Actual Spring 2014 Sand Smelt number = 1125 Actual Spring 2014 Sandeel number = % less Herring were caught during 2014 compared with 2013 (a reduction in 7289 individuals). A small number of fry (too small to positively identify) were caught. It is likely there were more of these fry were present, as they would have easily passed through the net % more Sandeels (representing 207 more individuals) were caught during In 2013 deployment issues with the seine net may have negatively impacted the figures. A small number of Bass were caught during Spring No Bass were seen during Spring Two species new to the survey were caught during Spring 2014 Worm Pipefish and Butterfish. 5

6 Actual Autumn 2014 Sand Smelt number = 1048 Actual Autumn 2014 Sand Goby number = 2943 Actual Autumn 2014 Bass number = 1864 The Herring catch remained low during the Autumn. 98.3% fewer Herring were caught during 2014 compared with more individual Sandeels were caught during 2014 compared with 2013 (1550% increase). As during the Spring, net deployment issues experienced during 2013 may have impacted this result % more Bass were caught during 2014 compared with One new species was caught during Autumn 2014 Red Mullet. 6

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8 Discerning patterns in fish species lengths remains difficult, but is likely to become clearer as data is added year upon year. The small number of Herring caught during June 2014 were longer on average than those caught during the previous 2 years, while the Herring caught in September 2014 were shorter on average than those caught the previous year. Large differences between the average length of fish caught during different years, as seen in Grey Mullet and Greater Pipefish, is most likely attributable to fish of different age classes being caught and measured having a large implication on the average length. 8

9 4.0 Key Findings during 2014 L-R: juvenile Bass, processing the catch, Lesser Weever During the 2014 survey season a total of 7837 fish representing 27 species were captured. Juvenile Clupeiformes (herring/sprat), commonly referred to as whitebait were caught in dramatically lower numbers than during either 2012 or A similar phenomenon was seen in the Chichester Harbour Small Fish Survey. Juvenile Bass were caught in dramatically higher numbers than during either 2012 or These high numbers reflect the importance of the harbour as a nursery ground. Three times as many Sandeel were caught in 2014 compared with This difference may in part be explained by technical issues encountered with seine net deployment during These fish represent a very important food resource for breeding seabirds. Over 1000 more individual Sand Gobies were caught in 2014 compared with A video camera trap set by the RSPB at tern breeding colony showed parents feeding this species to their chicks, as well as Clupeiformes and Sandeels. Three new fish species Butterfish, Red Mullet and Worm Pipefish were caught during the survey in 2014, bringing the total number of fish species caught in all years to 37. L-R: hauling in the seine net, processing the catch, towing the beam trawl 9

10 5.0 Metadata Water clarity is seen to be consistently lowest at Bedhampton. The presence of the aggregate wharf which is frequently visited by 70m vessels plus the adjacent input of the Hermitage Stream is likely to contribute to the poor water clarity here. During September 2014 maintenance dredging was in progress in this area which further added to water turbidity. Salinities remained fairly constant with those recorded in Temperatures were lower during 2014 which may be attributable to a change in recording device (glass thermometer used during 2014). The Met Office recorded higher air temperatures in 2014 compared with

11 6.0 Langstone and Chichester Comparison (Spring only) Catches in Langstone Harbour were compared with those in Chichester Harbour. As in previous years sites chosen for comparison offered the most similarities in terms of habitat. A similar array of species was caught at each compared site, reaffirming that the habitats are similar and host similar fish communities. The survey methodology used in Chichester Harbour is the same as that in Langstone. As seen in Langstone, Chichester Harbour revealed very small numbers of Herring in its catch compared to the previous year. During Spring 2013, more than 3500 Herring were caught at Copperas Point (more than 1500 caught at Bedhampton in Spring 2013). As illustrated in the above chart there were no Herring caught at Copperas Point in Spring 2013, and just 13 individual Herring were caught at Bedhampton during More than 100 Herring were caught at Pilsney Island during Spring 2013, which increased to 216 in the 2014 catch. At Eastney Point however the 2013 Spring catch of more than 1000 individual Herring was reduced in 2014 to less than 20 individual fish. 11

12 7.0 Species caught in Langstone Harbour during 2014 Fish Species Scientific name Locations caught Total number caught Ballan Wrasse Labrus bergylta EP 44 Bass Dicentrarchus labrax BW, EP, SS 1870 Black Goby Gobius niger EP 68 Brill Scopthalmus rhombus SS 2 Butterfish Pholis gunnellus EP 2 Common Goby Pomatoschistus microps BW, EP 24 Corkwing Wrasse Symphodus melops EP 25 Dover Sole Solea solea BW 4 Flounder Platichthys flesus BW 1 Greater Pipefish Syngnathus acus BW, EP, SS 10 Grey Mullet Liza aurata BW 6 Herring Clupea harengus BW, EP, SS 133 Lesser Weever Echiichythys vipera SS 10 Long Spined Sea Scorpion Taurulus bubalis EP 12 Plaice Pleuronectes platessa BW, EP, SS 4 Pollock Pollachius pollachius EP 1 Red Mullet Mullus surmeletus EP 2 Reticulated Dragonet Callionymus reticulatus EP 7 Sandeel Ammodytes tobianus SS 311 Sand Goby Pomatoschistus minutus BW, EP, SS 3031 Sand Smelt Atherina presbyter BW, EP, SS 2185 Shanny Lipophrys pholis EP 9 Short Spined Sea Scorpion Myoxocephalus scorpius EP 5 Solenette Buglossidium luteum SS 1 Sprat Sprattus sprattus BW 23 Worm Pipefish Nerophis lumbriciformes SS 2 Unidentified fry - EP 45 Species new to survey during 2014 Red Mullet Mullus surmeletus Worm Pipefish Nerophis lumbriciformes Butterfish Pholis gunnellus 12

13 8.0 GPS Imagery 13

14 9.0 Discussion The notable reduction in Herring fry numbers during 2014 is supported by anecdotal information from local fishermen. There have also been reports from the fishing community that 2014 was an extremely poor year for Mackerel, which would make sense a Mackerel predate upon bait fish such as Herring fry. Whilst it will require several more years of survey data to make an informed decision upon whether the 2014 Herring catch was exceptionally low, or if in fact 2012/2013 was exceptionally high, anecdotal evidence currently supports the former. Herring represent an important food source for many seabird species, including terns which breed in Langstone Harbour. The winter of 2013/14 was, according to the Met Office, the stormiest for 20 years, and the wettest since The Herring population in the English Channel spawn from November until February, peaking in December (Pawson, 1995). As the spawn of this species is stuck to the seabed it is possible stormy conditions negatively impacted the Herring eggs, contributing to low numbers of fry. Sandeels also represent an important food source for many fish and seabird species. These fish were caught in the highest numbers during the Langstone Harbour Small Fish Survey in Mechanical and equipment failures during previous survey years may have negatively impacted previous results, however good Sandeel numbers is good news as Sandeels represent significantly better quality food than Herring fry for Langstone Harbour s tern chicks in terms of calorific content (Yates, 2014). Bass were also caught in notably higher numbers than during previous years in Langstone Harbour. This observation was borne out by the CEFAS Solent Bass Survey 2014, during which 99% of the year 0 Bass caught during the survey were from a single site north Langstone Channel. The maintenance dredge which occurred at Bedhampton in September had a negative impact on the survey at that site. The dredge removed a large section of the sloped beach previously used to deploy the seine net, and loosened mud in the vicinity clogged the beam trawl, resulting in its abandonment. Visual surveys of the area at low water should take place prior to the 2015 survey. 11 species of fish which had been caught during previous years were not seen during 2014: Black Seabream, Fifteen Spine Stickleback, Garfish, Gilthead Seabream, Launce, Lumpsucker, Mackerel, Tompot Blenny, Transparent Goby, Tub Gurnard and Two-Spot Goby. None of these species were caught in large numbers in previous years. Sea Gooseberries Pleurobranchia pileus were caught in very large numbers in the Spring at both Eastney Point and Sword Sands. L-R: processing the catch, John Easterling, measuring a Bass, seine haul 14

15 10.0 Future Improvements The acquisition of a more effective set of aerators to use when large numbers of fish are caught will improve survival rates. The RSPB vessel Good Tern dramatically improved the success, consistency and safety of seine net deployment. All seine net deployment should occur from such a vessel in future. Utilising the same personnel to undertake metadata recording at each sample site helped to create more consistent metadata. Intermittent checks on metadata collection should be undertaken by the survey lead during 2015 to further improve accuracy. Consideration should be given to abandoning the Bedhampton Wharf site and replacing it with an alternative during the 2015season should be given, should visual surveys of the area since the maintenance dredge indicate that sampling may no longer be possible here. L-R: Dover Sole, Brill, processing the catch 11.0 Bibliography Brown M, & Armstrong, M. (2014). CEFAS Solent Bass Survey in Hayward P.J. & Ryland J.S. (2011). Handbook of the Marine Fauna North-West Europe. Oxford University Press, Oxford. Kay P, & Dipper, F. (2009). A Field Guide to the Marine Fishes of Wales and Adjacent Waters. Marine Wildlife, Llanfairfechan. Maitland P.S & Herdson D. (2009). Key to the Marine and Freshwater Fishes of Britain and Ireland. Environment Agency, Bristol. Pawson M. G (1995). Biogeographical identification of English Channel fish and shellfish stocks. Fisheries Research Technical Report (number 99). MAFF Direct Fisheries Research, Lowestoft. Yates, L. (2014). A Survey of the Feeding Activity of the Breeding Terns of Rye Bay. 15