Young Allis Shad Alosa alosa (Clupeidae) Would Not Be Euryphagous: An Assessment of Juvenile Diet and Prey Selectivity under Riverine-Type Conditions

Table 2

Number (N) and relative abundance (%N) of prey identified in the water samples, occurrence (%O), and mean relative abundance of prey inAlosa alosa stomach contents according to the age of fish (one month old or two months old) and the year (2018 or 2019).

	One month old								Two months old
	2018				2019				2018				2019
	Water		Allis shad (n = 22)		Water		Allis shad (n = 13)		Water		Allis shad (n = 25)		Water		Allis shad (n = 31)
	29 Jun		30 Jun		1 Jul		1 Jul		27 Jul		28 Jul + 1 Aug		31 Jul		31 Jul
	N	%N	%O	%N	N	%N	%O	%N	N	%N	%O	%N	N	%N	%O	%N
Cladocera	28	66.67	95.45	73.42	50	47.62	100.00	86.14	47	77.05	100.00	49.80	92	69.17	96.77	46.36
Copepoda (adults)	—	—	54.55	9.54	8	7.62	23.08	4.62	1	1.64	84.00	6.18	3	2.26	54.84	3.45
Copepoda (nauplii)	5	11.90	—	—	20	19.05	—	—	—	—	—	—	2	1.50	—	—
Diptera (adults)	4	9.52	4.54	0.35	—	—	15.38	0.73	—	—	40.00	2.52	1	0.75	22.58	1.54
Diptera (larvae)	—	—	72.73	15.53	3	2.86	38.46	5.43	1	1.64	96.00	18.43	4	3.01	80.65	17.84
Ostracoda	—	—	18.18	1.16	14	13.33	—	—	5	8.20	92.00	22.92	12	9.02	80.65	16.28
Hydrachnidia	—	—	—	—	2	1.90	—	—	—	—	—	—	4	3.01	25.81	1.58
Coleoptera	1	2.38	—	—	—	—	—	—	—	—	—	—	—	—	3.23	0.20
Terrestrial	—	—	—	—	1	0.95	7.69	3.08	5	8.20	—	—	1	0.75	3.23	0.27
Exuviae	4	9.52	—	—	2	1.90	—	—	1	1.64	—	—	2	1.50	—	—
Trichoptera (larvae)	—	—	—	—	—	—	—	—	1	1.64	4.00	0.16	—	—	—	—
Nematoda	—	—	—	—	1	0.95	—	—	—	—	—	—	—	—	—	—
Rotifera	—	—	—	—	4	3.81	—	—	—	—	—	—	12	9.02	12.90	2.65
Isopoda	—	—	—	—	—	—	—	—	—	—	—	—	—	—	45.16	7.30
Amphipoda	—	—	—	—	—	—	—	—	—	—	—	—	—	—	6.45	0.21
Gastropoda	—	—	—	—	—	—	—	—	—	—	—	—	—	—	3.23	2.32

Note: Terrestrial prey refers to nonaquatic prey items that fell into the artificial rivers. Results are indicated for all prey taxa sampled, whether in water or in fish. Values >33% calculated in fish stomach contents are marked in bold. The dates of water sampling and Alosa alosa capture are indicated for each group, along with the numbers of fish analysed (nonempty stomachs only, river R1 only).