Correction: Better or worse food: Nutrition value of the prey fishes and the potential health implications for Indo-Pacific humpback dolphins

There was a mistake in Figures 2 and 7 as published. There was a copy-paste error occurred when compiling the proximate composition working table used for statistical analysis: nutrient data for several fish species were misaligned, leading to incorrect results in Figure 2 and Figure 7. The corrected Figures 2 and 7 appear below.

There was a mistake in the caption of Figure 7 as published. “AAS” was incorrectly written as “ASS”. “Total” was incorrectly written as “Tatol”. The corrected caption of Figure 7 appears below.

“Summary of the dietary switch in the Zhuhai population of Indo-Pacific humpback dolphins and the potential nutritional risk. The arrows in the table indicate significantly higher (up-arrows) or lower (down-arrows) nutrition component in pelagic/neritic fishes compared with demersal fishes (p<0.05), while the circles indicate there is no significant difference. *: Duncan’s Multiple-Range Test of ANOVA; #: Kruskal-Wallis test. PUFA, Polyunsaturated fatty acids; MUFA, Monounsaturated fatty acids; SFA, Saturated fatty acids; DHA, Docosahexaenoic acid; EPA, Eicosapentaenoic acid; EAA, Essential amino acid; NEAA, Non-essential amino acids; TAA, Total amino acid; CS, Chemical score; AAS, Amino acid score; EAAI, Essential amino acid index.”

During our systematic re-review of the raw datasets, we found that a copy-paste error occurred when compiling the proximate composition working table used for statistical analysis: nutrient data for several fish species were misaligned, leading to incorrect results in Figure 2 and Figure 7.

After re-running all relevant analyses with the correct dataset, the core results related to energy density now differ from those originally reported:

1) In Zhuhai waters (home to the largest remaining Indo-Pacific humpback dolphin population), the energy density of pelagic/neritic prey fishes is significantly higher than that of demersal fishes, reversing the incorrect trend presented in the original Figure 2A and Figure 7.

2) In Jiangmen waters, the energy density of benthopelagic fishes is higher than that of pelagic/neritic fishes, but no statistically significant differences are observed between either group and demersal fishes.

A correction has been made to section 1 Introduction, final paragraph. The word “water” should be replaced by “ash”:

“In this study, we analyzed the proximate composition (moisture, ash, fat and protein), the fatty acids composition and the amino acid composition of the prey fishes of humpback dolphins and evaluated their nutritional status.

A correction has been made to section 2 Materials and methods, subsection 2.5 Statistical analysis, first paragraph. The word “error” should be replaced by “deviation”:

“The results are presented as mean values with their standard deviation (n = 5), and all above statistical analyses were performed using IBM SPSS 26.0 Statistics (IBM, USA).”

A correction has been made to section 3 Results, 3.1 Proximate composition of prey fishes, second paragraph. “Shantou” should be replaced by “Xiamen”:

“For example, the moisture contents of large yellow croaker (Pseudosciaena crocea) from Xiamen (77.76 ± 0.90%) are significantly higher than those from other habitats, especially Jiangmen (63.73 ± 1.09%) (Table S1).”

A correction has been made to section 3 Results, 3.1 Proximate composition of prey fishes, fourth paragraph:

“Comparison of the proximate composition among species niches in Zhuhai (Lingding Bay) and Jiangmen (western PRE) showed that the patterns of fish proximate composition differ between the two regions. In Zhuhai, the crude protein content of benthopelagic fishes was significantly higher than that of pelagic/neritic fishes (p < 0.05, Kruskal-Wallis test; Figure 2A), while the crude fat content of benthopelagic and pelagic/neritic fishes were significantly higher than that of demersal groups (p < 0.05, Kruskal-Wallis test; Figure 2A). Unlike the pattern in Zhuhai, benthopelagic fishes in Jiangmen had significantly higher fat content (p < 0.05, Kruskal-Wallis test), and exhibited the highest energy density, than pelagic/neritic groups, with no significant differences between benthopelagic and demersal groups, nor between pelagic/neritic and demersal groups (Figure 2B).”

Corrections have been made to 3 Results, 3.2 Fatty acids composition, first paragraph. “23” should be “31”, “12” should be “11”,

“A total of 31 kinds of the fatty acid were detected from 14 prey fish species of Indo-Pacific humpback dolphins, which included 11 saturated fatty acids (SFA), 9 monounsaturated fatty acids (MUFA) and 11 polyunsaturated fatty acids (PUFA) (Table S2).”

Corrections have been made to 3 Results, 3.2 Fatty acids composition, second paragraph. “Seven” should be “Twelve”, and the three instances of “PFA” should be “PUFA”:

“Twelve dominant fatty acids (more than 1% of total fatty acids) in the prey fishes were found: 14:0, 15:0, 16:0, 17:0 and 18:0 as SFA; 16:1, 17:1, C18:1n-9cis as MUFA; C18:2n-6cis, C20:3n-3, C20:5n-3 (EPA), C22:6n-3 (DHA) as PUFA. The average content of SFA, MUFA and PUFA is 57.09%, 33.49% and 8.71%, respectively (Table S2). The SFA, MUFA and PUFA contents of prey fishes varied significantly with species and location (p< 0.001).”

A correction has been made to section 4 Discussion, first paragraph. “lower energy densities” should be “higher energy densities”:

“In Zhuhai, the prey fishes were found to have higher energy densities, but poorer fatty acid and amino acid quality indices (PUFA content, PUFA/SFA ratio, DHA content, EAA content) in pelagic/neritic fishes compared with demersal ones.

A correction has been made to section 4 Discussion, second paragraph.

“Our results showed that the energy densities varied considerably with different species, with pelagicneritic and benthopelagic prey fishes having significantly higher energy densities compared to demersal fishes. Facing the decline of prey resource, the humpback dolphins would try to adjust their foraging strategy by expanding their targeting prey species to neritic and pelagic fish, however, as showed in Lin’s results, their overall foraging efficiency was still declining, not only in the prey availability and prey size (Lin et al., 2021), but also in terms of key nutrient quality (PUFA and EAA content), despite the higher energy densities of these prey types as revealed by our current study (Figure 2A).”

“However, consider the multiple lines of evidence (declining prey availability, smaller prey size, altered energy density profiles, poorer fatty acid and amino acid quality indices) suggesting potentially adverse outcomes, and the lessons drawn from Steller sea lion and harbour seals’ example, we indeed raise concerns about the health of dolphins. In fact, our continuous field survey in the past fifteen years on humpback dolphin population in the PRE indicated a much less newborns and juveniles in the eastern PRE (Zhuhai area) than the western area (Jiangmen area) (unpublished data). This phenomenon may be at least in part due to the food quality in the Zhuhai area, such as lower levels of PUFAs and EAAs rather than a lack of gross energy.”

Due to the aforementioned errors, some sentences in the Abstract need to be corrected. “catched” should be “caught” and “water” should be “ash” and “possessed lower energy density, PUFA” should be “possessed higher energy density but lower PUFA content”:

“In this study, we collected potential prey fishes caught by fishermen in six habitats of Indo-Pacific humpback dolphins and analyzed their proximate composition (moisture, ash, fat and protein),”

“In Zhuhai, home to the largest Indo-Pacific humpback dolphin population, pelagic/neritic prey fishes possessed higher energy density but lower PUFA content, PUFA/SFA ratio, DHA content, and EAA content compared to demersal fish, suggesting nutritional stress when there is a dietary switch from demersal to pelagic/neritic fishes in Zhuhai population.”

File Table S1 was erroneously published with the original version of this paper. The file has now been replaced.

The original version of this article has been updated.

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Footnotes

Edited and reviewed by: Xuelei Zhang, Ministry of Natural Resources, China