Variability in annual recruitment success as a determinant of long-term and large-scale variation in annual production of intertidal Wadden Sea mussels (Mytilus edulis)

Table 1 Mytilus edulis. Annual production (in kg AFDM m⁻² a⁻¹) by six separate cohorts (yearclasses 1969–1974, incl.) in a 1,100-m² mussel bed: before August 1969, between August 1969 and September 1970, between September 1970 and September 1971, etc., as estimated from mean individual weights (g AFDM) and numerical densities (10³ m^–²) recorded annually in late summer or early autumn (A August, S September, and O October)

Time of sampling	Cohort	Mean individual weight (g AFDM)	Density (10³ m⁻²)	Cohort production P (kg m⁻² a⁻¹)						Total Production
Time of sampling	Cohort	Mean individual weight (g AFDM)	Density (10³ m⁻²)	69	70	71	72	73	74	Total Production
				0.14						0.14
A69	1969	0.007	10
A69				1.5	0.002					1.5
S70	1969	0.19	6
	1970	0.004	0.3
				1.3	0.03	0.01				1.34
S71	1969	0.52	2
	1970	0.105	0.2
	1971	0.012	0.3
				0.1	0.01	0.01	0.003			0.12
O72	1969	0.59	0.5
	1970	0.165	0.1
	1971	0.07	0.1
	1972	0.015	0.1
				0.08	0.02	0.02	0.01	0.002		0.13
O73	1969	0.86	0.05
	1970	0.54	0.015
	1971	0.41	0.015
	1972	0.23	0.005
	1973	0.01	0.1
				0.03^a				0.16	0.006	0.20
S74	<73	1.17	0.04
	1973	0.40	0.6
	1974	0.014	0.2
Cohort totals and 6-year total P				3.15	0.06	0.04	0.01	0.16^b	0.01^b	3.43

^aIncludes the four cohorts born in 1969–1972
^bIndicates that the value is a serious underestimate of the life-time cohort production (because of early termination of observations)

ISSN: 1438-3888