Percophis brasiliensis, Quoy & Gaimard, 1825, Quoy & Gaimard, 1825

Bauer, Arthur de Barros & Fischer, Luciano Gomes, 2024, Trophic ecology of the demersal predator Brazilian flathead Percophis brasiliensis (Percophidae) in a coastal upwelling ecosystem, SW Atlantic, Neotropical Ichthyology 22 (2), pp. e 230115-e 230115 : e230115-230115

RESULTS

Sea surface temperature (SST) data recorded by the data logger confirmed the presence of upwelling events throughout the sampling period ( Fig. S1 ). The events occurred with greater intensity mainly in February, September and October with average temperatures close to 16°C.

Diet description. The non-empty stomachs corresponded to 49% (n = 496) of the total specimens collected and dissected (n = 1016) ( Tab. 1 ). Percophis brasiliensis ’ diet was composed of 37 prey taxa, of which 27 were identified at the species level ( Tab. 2 ). Teleostei was the most consumed prey group in %W for all ontogenetic groups, mainly composed of small pelagic fishes ( Clupeiformes ). The juveniles showed a higher percentage of Teleostei prey, 79.7%W, mainly composed by Engraulidae . For juveniles, crustaceans (mostly shrimps) and Cephalopoda (squids) represented 20.3%W of the prey. The importance of Teleostei is similar between young adults and adults (54.6 and 53.9%W, respectively), with an increase in crustaceans (27.0 and 15.5%W) and cephalopods (17.5 and 29.6%W).

We found significant differences among ontogenetic groups, seasons, and the interaction between these factors (PERMANOVA; p ≤ 0.03) ( Tab. 3 ). Dietary ontogenetic shifts have been detected but these changes vary according to the season. During Autumn and Winter, juveniles differed from young adults and adults (pairwise PERMANOVA; p ≤ 0.02). Only adults showed differences from the other two ontogenetic groups in the Summer (p ≤ 0.04). Juveniles and adults are different during Spring (p = 0.004), but we found no differences between juveniles and young adults, and young adults and adults (p = 0.10 and p = 0.49, respectively). Females (n = 348, 433.1 mm ± 69.2) were larger than males (n = 144, 365.2 mm ± 40.5; PERMANOVA, p = 0.001). However, no differences in diet were observed between males and females (Pseudo-F = 1.36, p = 0.33).

In juveniles, there was no significant differences in the diet throughout the year (p ≥ 0.081), while young adults’ diet differed among all seasons (p <0.01), except between winter and summer (p = 0.57) when similar %W of demersal fishes and non-identified fish were ingested ( Fig. 2 ). During the autumn, P. brasiliensis fed on the small pelagic shrimp Peisos petrunkevitchi Burkenroad, 1945 , while in the spring demersalpelagic cephalopods were the main prey group. The diet of adults during autumn was significantly different from all other seasons (p <0.01). Adults and young adults consumed a high proportion (%W) of P. petrunkevitchi during the autumn ( Figs. 2–3 ). Besides, during the autumn, the ingested prey number was four to 29 times higher than in other seasons for juveniles and adults ( Tab. S2 ). Despite the increase in prey number intake mainly between March and April, this pattern is not reflected in the %BW values ( Fig. S3 ). In all other seasons, larger fish have a more diverse diet ( Tab. S2 ).

Niche breadth of young adults and adults was smaller during Autumn, probably due to the large ingestion of a single species ( Tab. S2 ). For juveniles, the lowest calculated niche breadth was observed in Spring. In general, the niche breadth slightly decreases with growth, with mean values of standardized Levins’ index = 0.29, 0.27, and 0.26 in juveniles, young adults, and adults, respectively ( Tab. S2 ).

Stable Isotope Analysis. Percophis brasiliensis δ 13 C values ranged between -18.36 and -16.77 ‰, with a mean of -17.58 ± 0.26 ‰, while δ 15 N ranged between 11.91 and 14.29 ‰, with a mean of 13.52 ± 0.41 ‰ ( Tab. 4 ). Significant relationships were observed between δ 13 C (r 2 = 0.092, p = 0.030) and δ 15 N (r 2 = 0.645, p <0.001) versus total length ( Fig. 4 ).

Based on the measured standard ellipse corrected for small sample size (SEAc), the isotopic niche width decreases with the increase in fish size. Juveniles showed the broader niche (0.37), followed by young adults (0.34) and adults (0.28). The overlap area between juveniles and young adults was 37%, between young adults and adults was 53%, and between juveniles and adults was 28% ( Fig. 5 ).

Figures

FIGURE 1 | Location of the study area (in gray bordered by the dashed line), an upwelling ecosystem, SW Atlantic. The continuous line represents the isobaths of 10, 20, 50, and 100 meters deep.

FIGURE 2 | Seasonal variation in dietary composition (%W) for each ontogenetic group of Brazilian flathead Percophis brasiliensis. Seasons: Summer, Sum; Autumn, Aut; Winter, Win; Spring, Spr. Ontogenetic groups: Juvenile, Ju; Young adults, Ya; Adults, Ad.

FIGURE 3 | nMDS ordination plot of the Bray-Curtis similarity matrix based on the %W of prey groups of Brazilian flathead Percophis brasiliensis. Juveniles = white, young adults = gray, adults = black. Summer = triangle, Autumn = circle, Winter = square, Spring = inverted triangle. The main prey categories are represented by Spearman’s correlation vectors. The length of each vector provides the strength of the correlation coefficient, where the radius of the circle represents the maximum correlation (=1). Prey categories: PelCru = pelagic crustaceans, BenCru = benthic crustaceans, DemFish = demersal fishes, FisNI = non-identified fishes, and PelSqu = pelagic squids. Dotted lines represent the Bray-Curtis similarity of 68%.

FIGURE 4 | Relationships between total length (mm TL) versus δ15N values (‰; above) and total length versus δ13C values (‰; below) for Brazilian flathead Percophis brasiliensis. Juveniles (white circles), young adults (gray circles) and adults (black circles).

FIGURE 5 | Isotopic niche width and overlap of Brazilian flathead Percophis brasiliensis.

Tables

TABLE 2 | Diet composition of ontogenetic groups of Brazilian flathead Percophis brasiliensis. SL = Average standard length (mm), and TW = Average weight of predators (g), %N = Percentage in number, %W = Percentage in weight, %F = Frequency of occurrence. NI = Not identified.

Prey Items	Juveniles n = 124, SL = 292, TW = 137			Young adults n = 195, SL = 353, TW = 265			Adults n = 177, SL = 437, TW = 520
	%W %F %N			%W %F %N			%W %F %N
Pelagic prey	42.06	38.71	62.67	54.02	38.95	74.78	63.48	46.33	88.96
Crustaceans	6.85	4.84	44.45	15.64	10.26	69.04	11.67	11.3	84.9
Peisos petrunkevitchi Burkenroad, 1945	6.57	3.23	43.83	15.64	10.26	69.04	10.89	10.17	79.83
Sergestidae NI	0.28	1.61	0.62	0	0	0	0.78	1.13	5.07
Fishes	27.8	25.8	15.13	20.9	18.97	4.16	22.24	18.06	2.28
Anchoa sp.	1.34	1.61	0.62	1.45	2.05	0.26	0.06	0.56	0.05
Anchovia clupeoides (Swainson, 1839)	0	0	0	0.29	0.51	0.07	0	0	0
Carangidae NI	0	0	0	0.65	0.51	0.07	1.1	1.13	0.09
Chirocentrodon bleekerianus (Poey, 1867)	1.71	1.61	0.62	8.54	4.62	0.72	0.58	1.13	0.09
Clupeidae NI	0	0	0	0	0	0	1.39	0.56	0.05
Clupeiformes NI	7.54	4.84	3.09	0.6	0.51	0.07	2.76	2.82	0.23
Engraulidae NI	17.21	17.74	10.8	8.5	9.23	2.64	1.87	6.78	1.23
Engraulis anchoita Hubbs & Marini, 1935	0	0	0	0.59	1.03	0.26	0.11	1.13	0.09
Harengula clupeola (Cuvier, 1829)	0	0	0	0	0	0	5.29	0.56	0.09
Lycengraulis grossidens (Spix & Agassiz, 1829)	0	0	0	0.28	0.51	0.07	0	0	0
Sardinella aurita Valenciennes, 1847	0	0	0	0	0	0	7.5	2.26	0.27
Trachurus lathami Nichols, 1920	0	0	0	0	0	0	1.58	1.13	0.09
Cephalopoda	7.41	7.26	3.09	17.49	11.28	1.58	29.57	20.33	1.78
Doryteuthis pleii (Blainville, 1823)	0.26	1.61	0.93	15.22	4.62	0.66	24.27	14.12	1.14
Doryteuthis sp.	6.85	2.42	0.93	1.33	2.05	0.26	3.94	2.82	0.23
Lolliguncula brevis (Blainville, 1823)	0	0	0	0.39	3.08	0.46	0.1	1.13	0.09
Teuthida NI	0.3	3.23	1.23	0.54	1.54	0.2	1.26	2.26	0.32
Benthic/Demersal prey	16.81	27.45	14.22	31.19	37.97	18.06	24.15	53.59	7.47
Crustaceans	6.07	16.13	7.41	11.36	19.99	9.03	3.82	17.49	4.12
Artemesia longinaris Bate, 1888	0	0	0	0.35	1.54	0.2	0.32	1.69	0.37
Brachyura NI	0	0	0	0.01	0.51	0.07	0	0	0
Dendrobranchiata NI	2.93	10.48	4.94	2.22	5.64	7.18	0.73	4.52	2.78
Farfantepenaeus sp.	0	0	0	1.15	1.03	0.13	1.19	1.13	0.09

TABLE 3 | PERMANOVA results of the main effects between the factors ontogenetic groups and seasons of Brazilian flathead Percophis brasiliensis, estimated from Bray-Curtis similarity matrix based on %W. Significantly differences (p <0.05) are presented in bold.

Source	df	MS	Pseudo-F	P(perm)	Perm. (n)
Ontogenetic groups	2	16716	2.832	0.0288	9940
Season	3	19204	3.2602	0.0085	9941
Ontogenetic groups vs. Season	6	5946	1.5593	0.0176	9864
Residual	481	3813.3
Total	492