Evaluation of food competition and resource partitioning of recruiting fish with permanent residents in a seagrass habitat

Figures & data

Figure 1. Location of study site (King’s Beach, Barker Inlet) in relation to South Australian coastline (adapted from Cann et al. 2009).

Table 1. Monthly variations of water temperature, salinity and fish abundance with the same fishing effort (60 m trawling distance) at King’s Beach, Barker Inlet, South Australia.

Month	Temperature (°C)	Salinity (ppt)	Fish (n)
June July August September October November	11.7 11.1 12.2 20.8 17.9 20.4	38.0 38.5 38.8 38.8 40.0 40.5	155 28 168 51 176 244

Table 2. The abundance of benthic infauna and epifauna (mean ± SD, n = 6 per month) included in a sediment core area (86.6 cm²) at King’s Beach, Barker Inlet, South Australia (2007).

	June	July	August	September	October	November	Total
Amphipoda
Caprellid amphipod	0.2 ± 0.2	2.8 ± 2.8	4.3 ± 2.6	0	0.7 ± 0.3	0	13.9
Gammarid amphipod	18.5 ± 7.3	152.0 ± 25.8	61.5 ± 38.6	285.7 ± 64.8	79.5 ± 32.3	13.2 ± 2.8	982.0
Copepoda
Calanoid copepod	0	0	0	0	0	0	0
Cyclopoid copepod	12.8 ± 7.1	0	5.7 ± 4.4	0	0	0	30
Harpacticoid copepod	228.5 ± 42.4	1640.7 ± 148.2	880.5 ± 155.0	161.2 ± 56.5	62.8 ± 12.8	119.2 ± 10.5	3518.3
Porcelid harpacticoid	0	0	2.2 ± 2.2	0.3 ± 0.3	0.5 ± 0.5	0	6.0
Cumacea Cumacean	0	2.2 ± 2.2	2.7 ± 2.3	0	0	0	9.4
Decapoda Penaeid prawn	0.3 ± 0.2	0	0	0.2 ± 0.2	0	0.2 ± 0.2	1.1
Mysida Mysid shrimp	0	0	0	0	0.2 ± 0.2	0	0.4
Tanaidacea Tanaid	0	0	4.3 ± 2.2	0.2 ± 0.2	4.3 ± 2.3	0.2 ± 0.2	13.9
Mollusca Molluscan veliger	0	0	0	0	1.5 ± 1.0	0	2.5
Nematoda Nematode	109.3 ± 32.8	0	13.0 ± 8.6	3.5 ± 1.8	0.8 ± 0.7	5.7 ± 1.4	177.6
Polychaeta Errant polychaete	161.0 ± 48.6	73.0 ± 11.4	182.2 ± 48.9	134.2 ± 31.6	62.5 ± 34.8	9.5 ± 1.7	802.0
Sedentary polychaete	20.3 ± 6.7	18.7 ± 4.2	31.0 ± 17.2	5.5 ± 2.1	20.3 ± 5.8	34.5 ± 3.3	169.8
Total	551.0	2084.0	1669.4	590.8	323.8	202.6	5421.6

Table 3. Abundances of pelagic zooplankton (N m⁻³, mean ± SD) collected with a zooplankton trawl net at King’s Beach, Barker Inlet, South Australia (2007).

	June	July	August	September	October	November	Total
Amphipoda
Gammarid amphipod	0	3.6 ± 2.3	2.6 ± 2.6	47.2 ± 15.7	1.6 ± 1.6	0	55.0
Copepoda
Calanoid copepod	16.5 ± 7.2	25.7 ± 14.8	15.7 ± 6.8	293.6 ± 109.5	7.8 ± 1.5	332.9 ± 50.6	692.2
Copepod nauplii	203.6 ± 121.6	258.5 ± 28.1	733 ± 170.7	870.2 ± 299.0	237.5 ± 29.1	2131.0 ± 461.5	4433.8
Cyclopoid copepod	130.5 ± 91.6	92.8 ± 25.6	562.2 ± 164.7	256.9 ± 29.2	51.9 ± 16.6	1017 ± 112.1	2111.3
Harpacticoid copepod	597.6 ± 215. 7	476.4 ± 145.4	1425.9 ± 282.1	1986.6 ± 391.4	385.3 ± 55	3017 ± 207.1	7888.8
Mollusca
Molluscan veliger	0	0	0	0	196.6 ± 47.6	0	196.6
Polychaeta
Errant polychaete	0	10.5 ± 6.9	5.2 ± 5.2	10.5 ± 5.2	4.7 ± 2.7	5.2 ± 2.6	36.1
Polychaete larvae	80.2 ± 59.2	61.9 ± 19.1	783.7 ± 129.1	340.7 ± 51.7	23.6 ± 5.4	353.9 ± 136.4	1644.8
Total	1028.4	929.5	3528.3	3805.7	909.0	6857.7	17,058.6

Table 4. Monthly catch summary of fish species collected at King’s Beach, Barker Inlet, South Australia from June to November 2007.

Species	June	July	August	September	October	November	Total
Atherinidae
Atherinosoma microstoma	4	0	2	2	12	19	39
Clinidae
Heteroclinus adelaide (adult)	1	0	0	0	0	0	1
Heteroclinus adelaide (juvenile)	0	0	3	4	17	44	68
Engraulididae
Sprattus novaehollandiae	0	0	0	0	0	4	4
Gobiidae
Arenigobius bifrenatus	1	0	1	1	2	8	13
Bathygobius kreffti	0	0	0	0	0	9	9
Favonigobius lateralis	140	15	77	28	108	101	469
Gobiopterus semivestitus	1	0	1	0	1	0	3
Unidentified	0	0	0	0	4	13	17
Monacanthidae
Meuschenia freycineti	1	1	1	0	0	0	3
Mugilidae
Aldrichetta forsteri	0	0	5	0	0	0	5
Odacidae
Neoodax balteatus	1	1	1	0	0	0	3
Pleuronectidae
Rhombosolea tapirina	0	1	1	0	0	0	2
Scorpaenidae
Gymnapistes marmoratus (adult)	0	0	1	0	0	0	1
Gymnapistes marmoratus (juvenile)	0	0	0	0	1	15	16
Sillaginidae
Sillaginodes punctatus	3	3	0	10	15	3	34
Syngnathidae
Stigmatopora nigra	3	4	73	6	11	18	115
Vanacampus vercoi	0	0	0	0	3	5	8
Kaupus costatus	0	0	0	0	2	0	2
Terapontidae
Pelates octolineatus	0	3	1	0	0	0	4
Tetraodontidae
Contusus brevicaudus	0	0	1	0	1	0	1
Tetractenos glaber	0	0	0	0	0	5	5
Total	155	28	168	51	176	244	822

Figure 2. Individual prey types (%N) in the diet of the most common fish species captured in a seagrass bed in the Barker inlet from June 2007 to January 2008. *Other crustaceans include cumacean, tanaids and penaeid prawns grouped together.

Table 5. The occurrence (%) of each prey in the stomach of fishes collected at King’s Beach, Barker Inlet, South Australia from June 2007 to January 2008.

	S. punctatus 20–60 mm	S. punctatus 61–120 mm	S. punctatus >120 mm	F. lateralis	H. adelaide	G. marmoratus	S. nigra	A. microstoma	P. octolineatus
Fish sample size (n)	20	20	11	20	20	20	20	20	20
Amphipoda
Gammarid amphipod	80	76	0	40	100	75	55	50	0
Caprellid amphipod	0	0	0	0	5	0	0	5	5
Copepoda
Cyclopoid copepod	25	0	0	10	10	10	65	15	15
Calanoid copepod	15	0	0	0	0	5	60	5	0
Harpacticoid copepod	80	14	0	90	0	5	80	80	30
Porcelid harpacticoid	20	0	0	0	40	0	15	5	0
Copepod nauplii	5	0	0	0	0	0	0	15	0
Cirripedia
Barnacle nauplii	0	0	0	0	0	0	5	10	0
Cumacea
Cumacean	0	0	0	0	5	0	0	5	0
Decapoda
Penaeid prawn	0	5	0	0	10	10	0	5	0
Mysida
Mysid shrimp	5	0	0	0	10	5	0	5	0
Tanaidacea
Tanaid	0	0	0	0	5	0	0	0	0
Polychaeta
Polychaete worm	15	38	90	10	0	5	0	10	0
Plant material	0	0	0	0	0	0	0	0	80

Table 6. The range of fish length and mouth gape, mean stomach fullness rank and electivity index of fish caught between June 2007 and January 2008.

Fish species	Length (mm)	Mouth gape (mm)	Stomach fullness	Niche breadth				Electivity (εi)
					Cal	Cyc	Harp	Nau	Amp	Cru	Wor
Atherinidae
Atherinosoma microstoma	31–62	1.5–4.3	7 ± 1.8	0.02	−0.78	−0.90	0	−0.85	−0.04	−0.89	−0.86
Clinidae
Heteroclinus adelaide	23–46	1.8–4.5	7 ± 1.2	0.04	−1.00	−1.00	−0.69	−1.00	0.77	−0.51	−1.00
Gobiidae
Favonigobius lateralis	27–45	2.0–3.9	4 ± 3.0	0.02	−1.00	−0.91	0.54	−1.00	−0.24	−1.00	−0.9
Scorpaenidae
Gymnapistes marmoratus	18–26	2.5–4.4	4 ± 2.6	0.04	−0.87	−0.85	−0.97	−1.00	0.52	−0.35	−0.98
Sillaginidae
Sillaginodes punctata (20-60 mm)	17–45	0.8–2.8	5 ± 2.4	0.03	−0.72	−0.75	0.50	−1.00	0.05	−0.9	−0.76
S. punctata (61-120 mm)	84–112	3.0–6.0	5 ± 2.2	0.03	−1.00	-1.00	−0.89	−1.00	0.57	−1.00	−0.34
S. punctata (>120 mm)	177–203	6.0–9.0	7 ± 1.8	0.00	−1.00	−1.00	−1.00	−1.00	−1.00	−1.00	1.00
Syngnathidae
Stigmatopora nigra	67–100	0.7–1.1	6 ± 3.5	0.09	−0.22	0.17	0.03	−0.97	−0.78	−1.00	−1.00

Notes: Stomach fullness ranged from 0 (empty) to 10 (full). Niche breadth index values range from 0 (specialist) to 1 (generalist) in feeding. The food electivity (εi) ranges from −1 (avoidance) to + 1 (positive selection). Cal: calanoid, Cyc: cyclopoid, Har: harpacticoid, Nau: Nauplii, Amp: amphipod, Cru: other crustaceans, Wor: polychaete worms.

Table 7. Dietary overlap of King George whiting (Sillaginodes punctatus) at three size classes with other commonly occurring fishes in Barker inlet from June 2007 to January 2008.

	S. punctatus (20–60 mm)	S. punctatus (61–120 mm)	S. punctatus (>120 mm)
Atherinidae
Atherinosoma microstoma	0.075	0.489	0.003
Clinidae
Heteroclinus adelaide	0.1	0.870	0.001
Gobiidae
Favonigobius lateralis	0.965	0.095	0.013
Scorpaenidae
Gymnapistes marmoratus	0.17	0.885	0.031
Sillaginidae
S. punctatus (20–60 mm)	–	0.1	0.019
S. punctatus (61–120 mm)	0.235	–	0.115
S. punctatus (>120 mm)	0.019	0.115	–
Syngnathidae
Stigmatopora nigra	0.928	0.055	0
Terapontidae
Pelates octolineatus	0.4	0.13	0

Notes: Values 0–0.29 indicate low; 0.3–0.59 moderate; and ≥0.6 high dietary overlap. The values (>0.6) are bolded to show the trend of high dietary overlap.

Cann JH, Scardigno MF, Jago JB. 2009. Mangroves as an agent of rapid coastal change in a tidal-dominated environment, Gulf St Vincent, South Australia: implications for coastal management. Australian Journal of Earth Sciences. 56:927–938. doi: 10.1080/08120090903005386

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