Fish Ageing Survey Report The Gall Pond Our Ref:13#160 Date: 18/02/2014

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1 Fish Ageing Survey Report The Gall Pond Our Ref:13#160 Date: 18/02/2014 About this water The Gall Pond is a modest sized (2.25 acres) estate lake fishery, with an average depth of 7ft. It contains a range of coarse fish species including; common carp, common bream, tench, roach, and rudd. The lake also holds eels and the native predator, perch. Summary of age data The Gall Pond was sampled between March and June using rod and line methods. Scales from 65 fish were submitted. Of which there was 34 roach, 12 common bream, 9 perch, 4 tench and 1 common carp that were able to be aged. Unfortunately five fish could not be aged as the scales had been replaced at some point in the past. Scales that are lost from a fish are rapidly replaced, but unfortunately, the growth record is lost and therefore they cannot be aged. However of the sampled fish the roach, common bream, perch, tench and common carp were aged up to 9+, 13+, 9+, 11+ and 4+ respectively. Figure 1. Number of each species and their size range (mm), aged from 4+ to 13+. The fish sampled were between 88mm and 510mm long (Figure 1.). This is a good size range and helps to represent the fish populations at this water, in particular the roach. To improve these data, further scale samples could be taken from fish in the smaller size ranges (> 200mm) of common bream and tench and from the larger size classes (>150mm) of perch.

2 Average Length at Age As a part of our examination of fish scales, we can measure the mark ( annulus ) which shows the end of each year on the scales. We can then work out how long each fish was at the end of each year's growth. From this, we can calculate the average length at each age. The table below shows the estimated average length at age of the common bream, perch and roach. Age (years) Average length (mm) Common bream Perch Roach Percentage standard Growth values The average length at each age for the roach from The Gall Pond, were compared to the species standard for roach in Southern waters. The Percentage Standard Growth (PSG) was calculated to be 96% (Fisheries Technical Services, unpublished data). This means that the roach population is, overall, growing at 96% of the standard growth rate expected for this species, where 100% is the National average. This means that they have a just below average growth rate. Graph 1 shows the mean length at age for roach and how they compare to the national standard. The Perch showed a slow growth rate with a PSG value of 89% when compared to the species standard (Fisheries Technical Services, unpublished data). However there was a quantity of perch sampled was relatively low so analysis of the growth may not be fully representative of the population. The growth of the perch is shown in Graph 2. The common bream, however, showed fast growth with a PSG value of 111% when compared to the species standard (Hickley & Dexter, 1979). Like the perch though there was a limited sample size, which means that the analysis may not be representative of the population. The growth of the common bream can be seen in Graph 3. No PSG values were calculated for the common carp and tench due to the limited numbers of fish sampled. PSG values of between % are typically classed as average, slow is growth indicated by values of less than 90% and fast growth having PSG values of greater than 110%.

3 Graph 1: Growth rate of roach from The Gall Pond, compared to the standard growth rate for Southern rivers (Fisheries Technical Services, unpublished data). Graph 2: Growth rate of perch from The Gall Pond, compared to the national standard growth rate (Fisheries Technical Services, unpublished data).

4 Graph 3: Growth rate of common bream from The Gall Pond, compared to the national standard growth rate (Hickley & Dexter, 1979). Findings and Recommendations The roach within The Gall Pond were shown to be growing at a just below average rate. A PSG value of 96% is slower that the national average for this species. This could suggest that there may be too many roach within the lake, competing for the same resource, which will limit their growth potential. The broad size range of roach indicates that there must be successful recruitment of roach in the lake, particularly as the youngest fish are 2+ and <90mm. Conditions for the common bream within the lake are suitable as growth rates are well above the national average (110%). However there appears to be two distinct size groups of fish within the lake, <250mm and >400mm. This could be down to previous problems in recruitment, meaning some year classes are absent, or sampling bias. The perch had slow growth (89%). Predators such as these often play a vital role in controlling juvenile cyprinid numbers, creating more space and food availability for those left to proliferate and grow well. It is advised that the perch remain in the lake, for this purpose. The small sample size probably explains the slow growth rate as early year s exhibit much slower growth, as can be seen in Graph 2.

5 If you require any further advice on managing your fishery please contact your local area officer, Jody Armitage on Ageing Notation As the fish were sampled during the period April to September they have been aged using the plus (+) notation. Scale Image Roach (fish N o 38), 178mm, 5+. Annulus = Fisheries Technical Services - Fish Health, Ageing and Species, Environment Agency, Bromholme Lane, Brampton, Huntingdon, PE28 4N. Tel: ; Fax: ; fish.ageing@environment-agency.gov.uk