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Consultation relating to the 2025 Total Allowable Catch (TAC) for herring in the Firth of Clyde. The Marine Directorate of the Scottish Government is carrying out this consultation on behalf of the UK Fisheries Administrations to seek views on the level of the 2025 TAC.
Length information was collected from 693 herring and otoliths were taken and aged from 229 fish. Fish ranged in size from 18 to 31 cm, with a modal length of 27 cm (Figure A1). Landings consisted of fish spanning the full age range (1 – 10 years). Approximately 40% of the fish landed were four years or older.
Figure A1. Herring from the Firth of Clyde. Raised numbers at length and age in 2011 landings. Colour coding of vertical bars indicates the proportion of each age at a given length as indicated by colours in the legend.
2012:
A total of 679 herring were measured and 189 fish were aged (Table 2).
Fish ranged from 18 to 36 cm, with a modal length of 24 cm. Landings were dominated by fish between 1 – 3 years (Figure A2). The large landings from the outer Clyde consisted solely of smaller younger herring (modal length 23.5 cm and age range of 1 – 5 years, 95% of fish aged 3 or below). In contrast the landings from the inner Clyde were more similar in composition to 2011 (modal length 27.5 cm, spanning the full age range, 67% of fish landed were 4 years or older).
The dominance of the large sample from the outer Clyde resulted in the numbers at age in the landings being very different in 2012 compared to 2011. The proportion of fish at older ages in 2012 was much lower than in 2011, but this was entirely driven by the composition of the one large landing from the outer Clyde.
Figure A2. Herring from the Firth of Clyde. Raised numbers at length and age in 2012 landings. Colour coding of vertical bars indicates the proportion of each age at a given length as indicated by colours in the legend. Top panel shows the combined raised samples, middle and bottom panels show the composition of landings from the inner and outer Clyde.
2013:
Fish ranged from 11.5 to 29 cm, with a modal length of 27 cm that was similar to previous years. Landings were dominated by age 5 fish (35%,Figure A3).
Figure A3. Herring from the Firth of Clyde. Raised numbers at length and age in 2013 landings. Colour coding of vertical bars indicates the proportion of each age at a given length as indicated by colours in the legend.
Figure A4. Herring from the Firth of Clyde. Proportion of raised numbers at age in 2011 – 2013 commercial landings.
Figure A5. Herring from the Firth of Clyde. Length against age (winter rings) for individuals landed commercially in 2011 – 2013.
7.2 Discard Data
Figure A6. Discards of Clyde herring from the Nephrops fishery 2009 – 2019. Note that there are relatively few trips sampled each year, so estimates are highly variable.
Figure A7. Length frequencies of herring caught as bycatch in the Nephrops fishery in the Clyde from 2009-2019. Note that there were relatively few trips sampled each year, so estimates are highly variable.
7.3 Acoustic Surveys
Table A1. Estimated numbers (millions) and total biomass (Kt) of Clyde herring from acoustic surveys in July 1987 – 1990 and 2008 – 2009.
Age (year)
1987
1988
1989
1990
2008
2009
1
148.2
1.6
1.2
19.9
86
99
2
11.5
67.4
9.5
7.1
13
1
3
9.2
6.2
80.3
5.5
0
0
4
11.5
4.8
6.7
33.3
0
0
5
5.7
5.5
2.4
4.0
0
0
6
3
3.6
1.8
2.5
0
0
7
1.2
2.8
1.1
0.7
0
0
8
0.7
1.5
0.32
0.6
0
0
>9
0.4
0.4
0.1
0.2
0
0
Biomass
16.1
12.4
18.4
11.9
33
24
Figure A8. Time series of herring biomass in Clyde acoustic surveys. Surveys represented by blue bars were carried out by Marine Scotland, while surveys represented by green bars were conducted by AFBI (Northern Ireland). Surveys 1987 – 2009 were carried out in July, surveys from 2012 onwards were carried out in October/November. Note there was no survey in 2013 due to vessel breakdown.
*Total biomass results are unavailable for 2015 and 2018.
Figure A9. Age composition of herring in Clyde acoustic surveys. Surveys during 1987 – 2009 were carried out in July, surveys from 2012 onwards were carried out in October/November. Surveys in 2008/2009 were conducted by AFBI, other surveys were conducted by Marine Scotland Science. Note there was no survey in 2013 due to vessel breakdown. Age composition in 2015 and 2018 is known even though total biomass estimates are not available. Age 0 fish have been excluded for consistency as these were not reported quantitatively in the earlier surveys.
7.4 IBS length surveys (prior to 2020)
Figure A10. Proportion of herring at length from IBTS catches in Q1 and Q4, 2015 - 2019. Note there was no survey in Q4 during 2013.
Figure A11. Proportion of herring at length from IBTS catches in Q1 and Q4, 2010 - 2014. Note there was no survey in Q4 during 2010.
Figure A12. Proportion of herring at length from IBTS catches in Q1 and Q4, 2005 - 2009. Note there was no survey in Q4 during 2006.
Figure A13. Proportion of herring at length from IBTS catches in Q1 and Q4, 1990 - 2004. Note there were no surveys during Q4 1990 - 1996. No herring were caught during the Q4 2003 survey.
