Effects of sustainable diets on growth and gonad development in green sea urchins for echinoculture
This is a suggestion for a Degree Project for Bachelor's and Master's levels at the Department of Marine Sciences. Degree projects at the Department of Marine Sciences are done independently and must be written and assessed individually.
Subject: Marine biology
Start: Spring/Summer/Autumn 2026
Level: Master's thesis (30-60 hp), suitable for students in marine biology, ecology, or environmental science
Supervisors: Susanne Lindegarth, Nadjejda Espinel Velasco
Location: Tjärnö Marine Laboratory
Background
Kelp forests are highly productive ecosystems that support biodiversity, fisheries, and carbon storage. In many areas, kelp forests have shifted to sea urchin-dominated barren grounds due to overgrazing by Strongylocentrotus droebachiensis. While urchin removal can support kelp recovery, removed individuals are often discarded.
Sea urchin aquaculture (echinoculture) offers an opportunity to convert low-value urchins into high-value seafood through gonad enhancement ("roe production"). However, current feeding practices often rely on unsustainable resources such as wild-harvested algae or fish-based feeds. Developing sustainable, locally sourced diets-potentially using waste streams is therefore essential.
Project Description
This project investigates how different sustainable diets affect sea urchin growth and gonad development, with the aim of identifying efficient and environmentally friendly feed strategies.
Main research questions
- How does consumption differ between different types of feed: dulse (Palmaria), sea lettuce (Ulva), sugar kelp (Saccharina) and by-products from the fishing industry?
- How do different feed types affect the growth and survival of sea urchins over the experimental period?
- How do different feed types affect gonadal development and reproductive status in green sea urchins?
- Is there any feed type that provides a particularly good combination of high consumption, good survival, increased growth and favourable gonadal development?
Method
The experiment will be conducted in a controlled recirculating aquaculture system (RAS) at Tjärnö Marine Laboratory. Adult sea urchins will be exposed to different diet treatments, including algae-based diets (e.g. kelp or red algae with supplements) and a circular economy diet based on fishery discards. Urchins will be monitored for survival, growth (size and weight), gonad development (gonad index, yield), and gonad quality (colour, texture).
Expected outcomes
The project will identify sustainable diet options that maximize gonad yield and quality, supporting both aquaculture development and circular resource use. Results may also contribute to linking sea urchin harvesting with ecosystem restoration efforts.
Requirements
The work will be conducted at Tjärnö Marine Laboratory using indoor aquaculture systems. Some laboratory experience is beneficial. Interest in aquaculture, marine ecology, or sustainable food systems is recommended.