Impact of Fishing Exploitation and Climate Change on the Grey Mullet Mugil cephalus Stock in the Taiwan Strait

Figures & data

FIGURE 1. Annual trends of the (a) total catch and (b) percentage of Grey Mullet caught using purse seiners, gill nets, trail nets, and set nets and (c) the effort and CPUE of Grey Mullet caught using purse seiners in the Taiwan Strait.

TABLE 1. Length–age composition data of Grey Mullet in the Taiwan Strait.

Age	Length (cm) fromSu et al. (2002)	Length (cm) fromHuang et al. (2005)	Mean length (cm)
2	39.0	41.0	40.0
3	47.0	48.0	47.5
4	52.0	53.0	52.5
5	57.0	56.0	56.5
6	61.0	59.0	60.0

TABLE 2. Input parameters used for estimating the instantaneous rate of natural mortality for Grey Mullet in the Taiwan Strait.

Parameter	Value	Unit
β	2.769
	0.302
	8	Year
	2.416	Year
K	0.340	Year^−1
	−0.935	Year
M	0.428	Year^−1

FIGURE 2. Annual changes in population (black bars) and fishing mortality (gray line) for Grey Mullet in the Taiwan Strait, 1958–2004.

FIGURE 3. Relationships between (a)–(e) the CPUE and population, (f)–(j) population and fishing mortality, and (k)–(o) SSTA and recruitment numbers (ages 2–3) of Grey Mullet caught with varying M (0.50M, 0.75M, 1.00M, 1.25M, and 1.50M) in the Taiwan Strait, 1958–2003.

FIGURE 4. Changes in population at (a)–(f) ages 2–7 years for Grey Mullet in the Taiwan Strait, 1958–2004.

TABLE 3. Results of Pearson correlation analysis of the Grey Mullet population at ages 2–6 with varying M (0.50M, 0.75M, 1.00M, 1.25M, and 1.50M) against the annual mean Pacific Decadal Oscillation (PDO), Oceanic Nino Index (ONI), and winter sea surface temperature anomalies (SSTAs) for two periods (1958–1985, 1986–2004). An asterisk indicates significance at P < 0.05.

Population	Period
	1958–1985			1986–2004
	PDO	ONI	SSTA	PDO	ONI	SSTA
Age 2 (0.50M)	0.46*	−0.05	−0.01	0.20	0.29	−0.64*
Age 3 (0.50M)	0.61*	0.08	−0.15	0.65*	0.14	−0.77*
Age 4 (0.50M)	0.66*	0.10	−0.07	0.66*	0.12	−0.70*
Age 5 (0.50M)	0.30	−0.11	0.03	0.69*	0.16	−0.64*
Age 6 (0.50M)	0.17	−0.08	−0.12	0.75*	0.10	−0.61*
Age 2 (0.75M)	0.41*	−0.07	−0.04	0.15	0.21	−0.65*
Age 3 (0.75M)	0.57*	0.06	−0.21	0.65*	0.15	−0.78*
Age 4 (0.75M)	0.63*	0.08	−0.07	0.66*	0.12	−0.70*
Age 5 (0.75M)	0.27	−0.14	0.02	0.69*	0.16	−0.65*
Age 6 (0.75M)	0.15	−0.08	−0.11	0.73*	0.07	−0.63*
Age 2 (Base)	0.29	−0.09	−0.01	0.28	0.28	−0.67*
Age 3 (Base)	0.47*	−0.03	−0.15	0.60*	0.22	−0.79*
Age 4 (Base)	0.52*	−0.01	−0.07	0.66*	0.29	−0.71*
Age 5 (Base)	0.13	−0.25	0.03	0.61*	0.36	−0.68*
Age 6 (Base)	0.03	−0.13	−0.12	0.54*	0.31	−0.70*
Age 2 (1.25M)	0.25	−0.13	0.01	0.06	0.52	−0.68*
Age 3 (1.25M)	0.45*	−0.03	−0.16	0.65*	0.19	−0.79*
Age 4 (1.25M)	0.52*	−0.01	−0.07	0.66*	0.12	−0.71*
Age 5 (1.25M)	0.19	−0.20	−0.01	0.69*	0.17	−0.67*
Age 6 (1.25M)	0.12	−0.07	−0.14	0.69*	0.02	−0.66*
Age 2 (1.50M)	0.16	−0.17	0.04	0.02	0.22	−0.69*
Age 3 (1.50M)	0.36	−0.08	−0.13	0.65*	0.21	−0.80*
Age 4 (1.50M)	0.45*	−0.06	−0.06	0.66*	0.12	−0.72*
Age 5 (1.50M)	0.16	−0.22	−0.01	0.69*	0.18	−0.69*
Age 6 (1.50M)	0.12	−0.07	−0.15	0.69*	0.03	−0.67*

FIGURE 5. Cross-correlation function between recruitment numbers (ages 2–3) and (a), (c) average annual PDO and (b), (d) winter SSTAs for the periods 1958–1985 and 1986–2004. The two red dotted lines represent the limits of significance at the 5% level.

Su, W. C., C. S. Huang, L. J. Wu, and S. H. Hsieh. 2002. Length-age composition of Grey Mullet in 2000. Investigation and surveillance of Grey Mullet Resource of Taiwan. TFRI (Taiwan Fisheries Research Institute) Newsletter 156:9–10.

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Huang, C. S., J. C. Lin, and J. J. Huang. 2005. Length-age composition of Grey Mullet in 2004. Investigation and surveillance of Grey Mullet Resource. FRI (Fisheries Research Institute) Newsletter 9:1–5.

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