FISHERIES MONITORING PROGRAMME ENVIRONMENT AGENCY

Transcription

1 FISHERIES MONITORING PROGRAMME ENVIRONMENT AGENCY Eastern Area ANGLIAN REGION Needham Market 17/4/29 Fisheries survey report of the river Gipping (Temporal) 2 nd April 7 th May 29 H RICHARDS 18/11/29

2 SUMMARY Five sites were fished against the flow using Pulsed DC electric fishing gear between 2 nd April 7 th May 29. Fish fork lengths (mm) were measured and scales taken for ageing. Results are reported here using fish greater than 99mm as electro-fishing has been shown to be inefficient below this band. Further information can be found at Fifteen species and one hybrid were identified during the survey fish (>99mm) were caught. List of species caught: Roach x Bream Common bream Mirror carp Rudd 3-sp. Stickleback Dace Perch Ruffe Bullhead European eel Pike Stone loach Gudgeon Roach Tench The average density (number of fish in a given area) of all species (>99mm) over all sites fell from Ind./1m 2 in 28 to Ind./1m 2 in 29, a decline of 26.77%. Total average standing crop (weight of fish in a given area) fell from g/1m 2 in 28 to g/1m 2 in 29, a decline of 25.86%. Density (>99mm) composition Standing crop (>99mm) composition 1% 2% 9% 3% 6% 8% European eels 24% 3% Gudgeon 7% Perch 27% Pike 6% Roach % 58% 12% Tench 5% Others 29% Preliminary Assessment: In general, the fishery has improved since surveys began in Pike density has increased over time and significantly by 2.4% every year 21-29, standing crop has remained relatively stable. Densities of chub, perch and roach have also risen over this time but it is important to look at the bigger picture for roach where numbers have actually declined since Standing crop has also fallen for roach since 1989 with associated rises in chub and perch. Where to fish? Station Road Bridge is the place to be for roach where we caught 421 >99mm reaching 2lb. Those looking for chub should head to Needham Market, 32 >99mm caught, or Munton & Fison, 47 >99mm caught, where individuals reach up to 3lb. Good numbers of perch and pike were caught at Sproughton Intake and Bramford Lock with a 2lb pike roaming around at Bramford. A couple of sizeable tench were caught at Bramford Lock (42mm, 2.9lb) and Sproughton Intake (482mm, 4.5lb). A fairly large mirror carp of 712mm (18lb) was caught at Station Road Bridge. 2

3 5 sites were surveyed on the river Gipping between 2/4/29 and 7/5/29 (Figure 1/ Table 1). Table 1. Site details (measurements in metres). Site name Reference Survey date Length Width Area Midstream NGR Sproughton Intake IPS58 2/4/ TM13445 D/S Bramford Lock IPS51 6/5/ TM Station Road Bridge IPS514 16/4/ TM Needham Market IPS518 17/4/ TM94549 Munton & Fison IPS522 7/5/ TM6357 3

4 RESULTS The five sites were fished against the flow using Pulsed DC electric fishing gear. Fish fork lengths (mm) were measured and scales taken for ageing. Results are reported here utilising fish greater than 99mm as electro-fishing has been shown to be statistically inefficient below this band. Further information can be found at Density and standing crop. Fifteen species and one hybrid were recorded over the five sites surveyed between 2/4/29 7/5/ fish (>99mm) were caught. Density and standing crop of individual fish species are calculated using the number / weight of fish in each site area and then a mean (average) calculated for the reach, in this case 5 sites. Density is reported as the number of individuals of that particular species that might be found in 1m 2 of the river. Similarly, standing crop is the weight, or grams, of that fish species that might be found in the same area. The mean density of all species (>99mm) over all sites fell from Ind./1m 2 in 28 to Ind./1m 2 in 29, a decline of 26.77%. Total mean standing crop also fell from g/1m 2 in 28 to g/1m 2 in 29, a decline of 25.86%. The largest individual (mm) and species population estimate (>99mm) are recorded for chub, dace, perch, pike and roach at site level (Table 2). Table 2. Site specific population estimate (>99mm) and largest length (mm) for selected species. CHUB DACE PERCH PIKE ROACH Size (mm) No. Largest No. Largest No. Largest No. Largest No. Largest Sproughton Intake D/S Bramford Lock (19lb) Station Road Bridge (.4lb) (1.5lb) Needham Market (2.8lb) Munton & Fison (1.6lb) Largest fish from the survey were a 463mm (2.8lb) chub at Needham Market, a 239mm (.4lb) dace at Station Road Bridge, a 326mm (1.6lb) perch at Munton & Fison, a 958mm (19lb) pike d/s Bramford Lock and a 317mm (1.5lb) roach at Station Road Bridge. A couple of sizeable tench were caught at Bramford Lock (42mm, 2.9lb) and Sproughton Intake (482mm, 4.5lb). A mirror carp of 712mm (18lb) was caught at Station Road Bridge. 4

5 Roach were, by far, the most common fish greater than 99mm over the five sites reaching 8 individuals for every 1m 2 of the river surveyed, or a 57.15% share of the fish population, followed by pike (11.72%), chub (8.9%), European eels (7.86%) and perch (7.29) Bullhead, gudgeon, stone loach and 3-spined stickleback were also abundant at sizes below 99mm (Figure 2a). 9 Figure 2a. Mean density of fish (>99mm) on the temporal river Gipping 29 (n=5) 8 7 Density (Ind./1m 2 ) European eels Gudgeon Perch Pike Roach Tench Others Surprisingly, pike are dominant by weight, mainly due to a few large individuals, with a mean of approximately 641g for every 1m 2 of the river or a 28.52% share of the standing crop. Roach and chub follow with 27.23% and 23.64% shares respectively (Figure 2b). 7 Figure 2b. Standing crop of fish (>99mm) on the temporal river Gipping 29 (n=5) 6 Standing crop (g/1m 2 ) European eels Gudgeon Perch Pike Roach Tench Others 5

6 Trends in density and standing crop. Data has been collated from all surveys between 21 to 29 to identify potential trends in fish density (Figure 3) and standing crop (Figure 4) from the five temporal sites on the river Gipping Figure 3. Density of fish species (>99mm) on the river Gipping (n=5) Density (Ind./1m 2 ) Dace Eels Perch Pike Roach density has remained relatively stable over the five sites although standing crop has decreased.. Historically, dace have performed poorly on this reach and therefore no trends can be identified. Perch density and standing crop have both increased over the nine survey years, density rising by approximately 2% every year and standing crop by as much as 9% respectively every year. Pike density* has risen significantly by 2.4% every year, whereas standing crop* has remained relatively stable at approximately 8g/1m 2. Roach density and standing crop have both returned to mean levels after the high of Figure 4. Standing crop of fish species (>99mm) on the river Gipping (n=5) 16 Standing crop (g/1m 2 ) Dace Eels Perch Pike Roach

7 Care must be taken when looking at temporal data as it only provides a snapshot of potential trends or cycles, in this case 9 years. For example, the temporal data illustrates a rise in eel densities and standing crop where, in fact, both have declined dramatically as shown in the spatial data (Figure 5) with standing crop* significantly falling by 5.2% every year since 1989 to Figure 5. Density and standing crop* (log+1) of eels (>99mm) on the river Gipping (n=5) Density log+1 (Ind./1m 2 ) Standing crop* log+1 (g/1m 2 ) If we consider the huge rise in roach density and standing crop between 27 and 28 and look at the spatial data for density since 1989 the rise is not unusual (Figure 6). The data suggests a 6-8 year cycle for roach so the temporal data only provides one rise or fall of that cycle. 1.8 Figure 6. Density (log+1) of roach (>99mm) on the river Gipping (n=5) Density log+1 (Ind./1m 2 )

8 Length frequency distributions. The lengths of fish measured during the survey programme can be collated to produce a frequency distribution. These can be used to identify population age structure and potential strong year classes (Figure 7). Scales were taken from 3 fish for every 1cm band (where possible) for chub, dace and roach and mean length at age is provided where available. This report has concentrated on fish above 99mm but these distributions encompass all fish caught. The fishing method used has been shown to be inefficient at catching fish below 99mm in length. The mesh sizes on the landing and stop nets are also too large to allow efficient catches below this 99mm band. Therefore small fish <99mm are under represented and their distributions should be looked at with caution. Number of fish Figure 7. Length frequency distribution of fish species by 5mm size bands on the river Gipping 29 (n=5) with mean length at age where available CHUB DACE Number of fish PERCH Number of fish

9 PIKE Number of fish ROACH N um be r of fish Fish length (mm) Dace mature at around 3-4 years of age with a maximum age of 1 years. This relatively short-lived species exhibits a typical decline in year classes, starting with large numbers of early year classes gradually declining to a few older fish around 5-6 years of age. Roach live slightly longer, maximum 18 years, and mature at 2-4 years for males and 3-5 years for females. Their distribution is slightly longer with fish still being caught at around years of age. A roach of 12+ (1996) years of age was caught at Station Road measuring 317mm. mature at 3-7 years for males and 4-8 years for females and can live as long as 22 years. Their distribution demonstrates a longer lived species with possible strong year classes at 4 (24) and 9 (1999) years of age. A chub of 13+ years of age (1995) was caught at Needham Lake measuring 447mm. If you have any questions regarding anything in this report, please contact the fisheries team on Tel: