Inter- and intra-specific trophic interactions of coastal delphinids off the eastern coast of South Africa inferred from stable isotope analysis

Michelle Caputo; Thibaut Bouveroux; Megan van der Bank; Geremy Cliff; Jeremy J Kiszka; Pierre William Froneman; Stephanie Plön

doi:10.1016/j.marenvres.2022.105784

Inter- and intra-specific trophic interactions of coastal delphinids off the eastern coast of South Africa inferred from stable isotope analysis

Mar Environ Res. 2022 Dec:182:105784. doi: 10.1016/j.marenvres.2022.105784. Epub 2022 Oct 21.

Authors

Michelle Caputo¹, Thibaut Bouveroux², Megan van der Bank³, Geremy Cliff⁴, Jeremy J Kiszka⁵, Pierre William Froneman⁶, Stephanie Plön⁷

Affiliations

¹ SARChI Chair in Marine Ecology, Department of Zoology and Entomology, Rhodes University, P.O. Box 94, Grahamstown, 6140, South Africa; Institute of Environment, Department of Biological Sciences, Florida International University, 3000 NE 151 St, North Miami, FL, 33181, USA. Electronic address: mcaputo@fiu.edu.
² Dauphin Island Sea Lab, 101 Bienville Blvd., Dauphin Island, 36528, USA.
³ Eastern Cape Parks and Tourism Agency, East London, P.O. Box 11235, Southernwood, East London, 5213, South Africa; South African National Biodiversity Institute, Private Bag X7, Claremont, Cape Town, 7735, South Africa.
⁴ KwaZulu-Natal Sharks Board, Umhlanga Rocks, 4320 and School of Life Sciences, University of KwaZulu-Natal, Durban, South Africa.
⁵ Institute of Environment, Department of Biological Sciences, Florida International University, 3000 NE 151 St, North Miami, FL, 33181, USA.
⁶ SARChI Chair in Marine Ecology, Department of Zoology and Entomology, Rhodes University, P.O. Box 94, Grahamstown, 6140, South Africa.
⁷ Department of Pathology, Stellenbosch University, South Africa; Bayworld Centre for Research and Education (BCRE), Gqeberha, South Africa.

PMID: 36306553
DOI: 10.1016/j.marenvres.2022.105784

Abstract

Dietary tracers, such as bulk stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopes, can be used to investigate the trophic interactions of marine predators, which is useful to assess their ecological roles within communities. These tracers have also been used to elucidate population structure and substructure, which is critical for the better identification of management units for these species affected by a range of threats, particularly bycatch in fishing gears. Off eastern South Africa, large populations of Indo-Pacific bottlenose (Tursiops aduncus) and common dolphins (Delphinus delphis) co-occur and are thought to follow the pulses of shoaling sardines (Sardinops sagax) heading north-east in the austral winter. Here we used δ¹³C and δ¹⁵N to investigate the trophic interactions and define ecological units of these two species along a ≈800 km stretch of the east coast of South Africa, from Algoa Bay to the coast of KwaZulu-Natal. Common and bottlenose dolphin dietary niche overlapped by 39.7% overall in our study area, with the highest overlap occurring off the Wild Coast (40.7% at Hluleka). Both stable isotopes were significantly enriched in bottlenose dolphins sampled in the western part of our study area (i.e., Algoa Bay and Amathole) compared to eastern animals (i.e., from Hluleka, Pondoland, and KZN). In areas where genetic information is not available or is insufficient, food web tracers (such as stable isotopes) can be used to group individuals based on trophic ecology, which can provide ecological units for management of populations. The distinct isotope signatures found here for bottlenose dolphins can, therefore, be used as management units for conservation efforts in the future.

Keywords: Delphinus delphis; Dietary niche analysis; SIBER; Sardine run; South Africa; Tursiops aduncus.

MeSH terms

Animals
Bottle-Nosed Dolphin*
Isotopes
Nitrogen
Nutritional Status
South Africa

Substances

Isotopes
Nitrogen