Population structure and dynamics of Orchestia montagui (Crustacea: Amphipoda) in the Bizerte lagoon (northern Tunisia)

Figures & data

Figure 1. Sampling locality: 37°13′8′′ N, 09°55′1′′E (Bizerte, Tunisia).

Figure 2. Monthly variation of temperature at the sampling site during the study period.

Figure 3. Population structure of Orchestia montagui in the supralittoral zone.

Table I. Categories and sex ratio of the Orchestia montagui population in the supralittoral zone of Bizerte lagoon, Tunisia.

Month	Immature	Males	Non-reproductive females	Females with empty marsupium	Ovigerous females	Sex ratio M/F	χ^2	p
July	21	212	9	10	136	1.37	17.706	< 0.0001
August	0	152	4	19	58	1.88	43.27	< 0.0001
September	74	131	25	16	59	1.31	8.32	0.004
October	11	88	32	30	29	0.97	0.101	0.751
November	0	37	26	20	16	0.60	12.626	0.000
December	17	65	0	25	30	1.18	1.667	0.197
January	20	56	14	66	35	0.49	40.713	< 0.0001
February	54	128	10	30	41	1.58	21.139	< 0.0001
March	74	50	7	11	60	0.64	12.25	0
April	77	187	0	7	46	3.53	149.633	< 0.0001
May	97	151	13	14	51	1.94	46.541	< 0.0001
June	85	121	24	15	50	1.36	9.752	0.002
Total	530	1378	164	263	611	1.33	95.695	< 0.0001

Figure 4. Relation between body length (LT) and cephalic length (CL) of Orchestia montagui.

Figure 5. Monthly variation of ovigerous females (%) of Orchestia montagui in the supralittoral zone.

Figure 6. Size-frequency distribution of Orchestia montagui from the supralittoral zone. Inverted triangle indicates average cephalic length (CL) of the numbered cohorts or groups of cohorts; black bar indicates ovigerous females; a-l represent the size-frequency distribution of O. montagui in each month.

short-legendFigure 6.

Figure 7. Estimated growth and life span of Orchestia montagui cohorts or groups of cohorts (average cephalic length, CL ± standard deviation) in the supralittoral zone. Broken lines indicate probable cohort merging or cohort evolution in time.

Figure 8. Recruitment profile of Orchestia montagui in the supralittoral zone.