The mechanisms leading to ontogenetic diet shift in a microcanivore, Pterogobius elapoides (Gobiidae)

Figures & data

Figure 1.  The serpentine goby, Pterogobius elapoides, hovering to search prey on the bottom in the ocean around Kurahashi Island, Japan.

Figure 2.  Comparison of numeric (shaded bar) and volumetric (empty bar) occurrence (presented as relative frequencies;%±standard deviation) of major dietary items found in the stomach contents among three size classes investigated.

Table 1. Individual numbers, numeric occurrence (%; in bracket), and mean sizes (mm±standard deviation) of the taxa collected from water column, alga, and substratum in the study site.

	Prey available from the environments
	Individual number (%)	Mean body size±SD
Water column
Copepoda
Calanoida
Palacalanus spp.	1487 (56.6)	0.6±0.17
Copepodid stages	289 (11.4)	0.6±0.19
Nauplii	286 (10.9)	0.4±0.22
Calanus spp.	43 (1.6)	1.8±1.22
Poecilostomatoida
Corycaeus sp.	85 (3.2)	0.7±0.08
Cyclopoida
Oithona spp.	128 (4.9)	0.5±0.08
Harpacticoda
Euterpina sp.	45 (1.7)	0.6±0.06
Others (Copepoda)	85 (3.2)	0.7±0.34
Cladocera
Evadne sp.	25 (1.0)	0.7±0.10
Appendicularia
Oikopleura ssp.	98 (3.7)	5.7±1.67
Others	42 (1.6)	1.1±0.73
Algal collections
Amphipoda
Pontogeneia ssp.	1571 (52.7)	1.8±0.64
Caprella ssp.	234 (7.9)	16.4±17.63
Mysidacea	28 (0.9)	4.5±1.63
Copepoda
Harpacticoda	1016 (34.1)	0.7±0.07
Crustacea
Tanaidecia	85 (2.9)	2.2±1.08
Others	48 (1.6)	2.7±1.55
Benthic substratum
Amphipoda
Melita ssp.	6196 (10.7)	2.0±1.11
Corphium sp.	2327 (4.0)	3.1±1.56
Maera sp.	1004 (1.7)	3.8±1.23
Grandidierella sp.	976 (1.7)	2.4±0.54
Other (Amphipoda)	429 (0.7)	2.7±1.81
Copepoda
Harpacticoida	42878 (74.1)	0.7±0.05
Cumacea	447 (0.8)	3.1±0.71
Polychaeta	2893 (5.0)	22.7±16.40
Ostracoda	684 (1.2)	1.0±0.11

Table 2. Ontogenetic changes in using different types of foraging behavior by serpentine gobies, that is, capturing in mid-water (CM), sucking algal invertebrate (SA), and picking benthic invertebrates (PB).

Size class	CM	SA	PB
Small	25.38±21.95 (80.08%)	2.59±2.10 (19.92%)	0 (0%)
Medium	3.46±2.30 (25.37%)	11.47±8.98 (59.94%)	1.96±1.29 (14.69%)
Large	0 (0%)	0 (0%)	9.64±7.77 (100.00%)
Note: Values indicate frequency of the behavior per 10 min (mean±standard deviation) and are also presented on percentage basis (%).