Relating a recruitment shift of Patagonian grenadier (Macruronus magellanicus Lönnberg) to large-scale environmental changes off Southern Chile

Figures & data

Figure 1 A, Geographic distribution range of Macruronus magellanicus around South America and main oceanic currents in the SE Pacific. B, Study area showing the 1×1° cells and specific geographical domains used to compute SSTA averages along the Chilean coast. WWD-B = west wind drift bifurcation, HC = Humboldt Current, CHC = Cape Horn Current, ACC = Antarctic Circumpolar Current, ONA = oceanic nursery area (hypothetical), ENA = estuarine nursery area, MSA = main spawning area.

Figure 2 A, Time series of SSB. B, One-year-old fish recruitment of Macruronus magellanicus off southern Chile (1980–2010). Dotted lines are indicative of regime shifts identified in Table 1.

Figure 3 Annual averages of SSTA in coastal waters of the SE Pacific Ocean (35°S–47°S) from 1981 to 2010. Data intended to represent the first months of life of Macruronus magellanicus, from July to December. Colour scale on the right indicates temperature anomaly in °C.

Table 1 Detection of shifts in sea-surface temperature anomaly (SSTA), latitudinal position of the west wind drift bifurcation (WWDL), southern oscillation index (SOI), spawning stock biomass (SSB) and recruitment time series (1981–2010).

	Chronological clustering		Bayesian change point		Relative change
Response variable	Shift year	P value	Shift year	Posterior prob.	(Regime 2– regime 1)
SSTA
Fishing area	1998	<0.001	1998	0.89	−0.65 °C
Shelf nursery area	1998	<0.01	1998	0.68	−0.47 °C
Estuarine nursery area	1998	<0.01	1998	0.93	−0.79 °C
Spawning area	1998	<0.01	1998	0.92	−0.57 °C
WWDL	1995	<0.001	1995	0.32	+2.13 °S
SOI	1999	>0.1	1999	0.11	+0.88
loge(R)	2000	<0.05	2000	0.82	−0.87
loge(SSB)	2002	>0.1	1982	0.79	−0.78
loge(R/SSB)	1998	<0.05	1998	0.75	−0.25

Note: P values for chronological clustering correspond to the maximum likelihood ratio between autoregressive (order one) mixed models, fit with and without the corresponding shift. Shift years correspond to those that exhibited the maximum likelihood or the highest posterior probability to represent a shift within each series.

Figure 4 A, Observed relationships between hind-cast recruitment rates (R/SSB) of Macruronus magellanicus and SSTA in its main fishing area 1981–2008 and predicted values from an auto-regressive linear regression model. B, Relationship between hind-cast recruitment (R, in millions) and SSB (in tonnes) during the same period, and predictions from a non-linear conditional Ricker's (1954) S-R model. Year 2008 is highlighted in both panels as an anomalous year, although it was not excluded from any analysis.

Ricker WE 1954. Stock and recruitment. Journal of the Fisheries Board of Canada 11: 559–623. 10.1139/f54-039

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