Predicting Impacts of Offshore Monoculture Farm Expansion in Ultra-Oligotrophic Waters of the Levantine Basin

Leigh Livne,Ofira Ayalon,Dan Tchernov,Michal Grossowicz

doi:10.3389/fmars.2020.00556

Abstract

The aim of this brief research report was to define the consequential shifts in biomass and trophic structure of an ecosystem surrounding an offshore monoculture fish farm in Israel. It attempts to clarify the impact of the industry expansion and input of artificial fish pellets on functional group biomasses. We account for the direct addition of artificial food pellets, as well as metabolic wastes from the caged fish in a mass-balance food web model (Ecopath), as well as the temporal expansion of the farm’s production capacity to 21,000 t over a 30-year period (Ecosim). In the former static mass-balance model of the food web, the addition of the fish cages at its current production size of 1000 t does not adversely affect the system, and trophic energy transfer is still dependent on primary production versus the detrital pathway. The model suggests a semi-stable ecosystem with low trophic interactions. With time, the increase in fish farming at the site is characterised by an increase of all functional group biomasses at the site over the 30-year period. The accumulation in detritus most notably correlates to greater biomass for all benthic functional niches and their secondary consumers. It is, therefore, apt to develop an indicator species list to indicate negative site disturbance. In summary, the sediment column condition will be the indicator for ecosystem stability, as well as large predator attraction to the cages from the input of artificial pellets and the accumulation of dead fish at the cage bottom.

Highlights

Aquaculture is a growing industry throughout many areas of the world (Duarte et al, 2009), with a reported 54.1 million tonnes (t) of finfish farmed in marine and coastal waters in 2016 (FAO, 2018)
This study focuses on the present-day trophic flow and community structure of an ecosystem surrounding an offshore fish farm
We addressed identifying in trophic structure, defined which impacts were greatest to the marine system, and how these sit within a management context for Israel, considering results from previous local studies

Summary

Introduction

Aquaculture is a growing industry throughout many areas of the world (Duarte et al, 2009), with a reported 54.1 million tonnes (t) of finfish farmed in marine and coastal waters in 2016 (FAO, 2018). Impacts From Fish Farming in the Levant Basin. 1,000 t of gilthead sea bream (Sparus aurata), and the farm is projected to produce 21,000 t over 14 km of space in the two decades. In a heavily impacted marine region such as the Levantine Basin, ecosystem-scale models are beneficial when combined with niche micro-research objectives, and Ecopath with Ecosim (hereafter abbreviated to EwE, Christensen et al, 2005) models provide a common infrastructure to accomplish this and apply it to sustainable management and policy

Methods

Results

Conclusion