Modelling transport of inshore and deep-spawned chokka squid (Loligo reynaudi) paralarvae off South Africa: the potential contribution of deep spawning to recruitment
- Authors: Downey-Breedt, Nicola , Roberts, Michael J , Sauer, Warwick H H , Chang, N
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/125183 , vital:35742 , https://doi.10.1111/fog.12132
- Description: The South African chokka squid, Loligo reynaudi, spawns both inshore (≤70 m) and on the mid-shelf (71–130 m) of the Eastern Agulhas Bank. The fate of these deep-spawned hatchlings and their potential contribution to recruitment is as yet unknown. Lagrangian ROMS-IBM (Regional Ocean Modelling System-Individual-Based Model) simulations confirm westward transport of inshore and deep-spawned hatchlings, but also indicate that the potential exists for paralarvae hatched on the Eastern Agulhas Bank deep spawning grounds to be removed from the shelf ecosystem. Using a ROMS-IBM, this study determined the transport and recruitment success of deepspawned hatchlings relative to inshore-hatched paralarvae. A total of 12 release sites were incorporated into the model, six inshore and six deep-spawning sites. Paralarval survival was estimated based on timely transport to nursery grounds, adequate retention within the nursery grounds and retention on the Agulhas Bank shelf. Paralarval transport and survival were dependent on both spawning location and time of hatching. Results suggest the importance of the south coast as a nursery area for inshore-hatched paralarvae, and similarly the cold ridge nursery grounds for deep-hatched paralarvae. Possible relationships between periods of highest recruitment success and spawning peaks were identified for both spawning habitats. Based on the likely autumn increase in deep spawning off the Tsitsikamma coast, and the beneficial currents during this period (as indicated by the model results) it can be concluded that deep spawning may at times contribute significantly to recruitment.
- Full Text:
- Date Issued: 2016
Studying the impact of ocean eddies on the ecosystem of the Prince Edward Islands: DEIMEC ll
- Authors: Pakhomov, Evgeny A , Ansorge, Isabelle J , Kaehler, Sven , Vumazonke, Lukhanyiso U , Gulekana, K , Bushula, T , Balt, C , Paul, D , Hargey, N , Stewart, H , Chang, N , Furno, L , Mkatshwa, S , Visser, C , Lutjeharms, Johan R E , Hayes-Foley, P
- Date: 2003
- Language: English
- Type: Article
- Identifier: vital:6932 , http://hdl.handle.net/10962/d1011952
- Description: The Dynamics of Eddy Impacts on Marion’s Ecosystem Study (DEIMEC) programme was begun in 2002 with the aim of understanding the importance of the oceanic, upstream environment to the ecosystem of the Prince Edward Islands. This island group consists of two small volcanic islands and provides many opportunities for studying ecological and evolutionary processes, for monitoring ecological changes in relation to global climate change and for conserving a unique component of the planet’s biological diversity.
- Full Text:
- Date Issued: 2003