Gill Damage to Atlantic Salmon (Salmo salar) Caused by the Common Jellyfish (Aurelia aurita) under Experimental Challenge

Abstract

BackgroundOver recent decades jellyfish have caused fish kill events and recurrent gill problems in marine-farmed salmonids. Common jellyfish (Aurelia spp.) are among the most cosmopolitan jellyfish species in the oceans, with populations increasing in many coastal areas. The negative interaction between jellyfish and fish in aquaculture remains a poorly studied area of science. Thus, a recent fish mortality event in Ireland, involving Aurelia aurita, spurred an investigation into the effects of this jellyfish on marine-farmed salmon.Methodology/Principal FindingsTo address the in vivo impact of the common jellyfish (A. aurita) on salmonids, we exposed Atlantic salmon (Salmo salar) smolts to macerated A. aurita for 10 hrs under experimental challenge. Gill tissues of control and experimental treatment groups were scored with a system that rated the damage between 0 and 21 using a range of primary and secondary parameters. Our results revealed that A. aurita rapidly and extensively damaged the gills of S. salar, with the pathogenesis of the disorder progressing even after the jellyfish were removed. After only 2 hrs of exposure, significant multi-focal damage to gill tissues was apparent. The nature and extent of the damage increased up to 48 hrs from the start of the challenge. Although the gills remained extensively damaged at 3 wks from the start of the challenge trial, shortening of the gill lamellae and organisation of the cells indicated an attempt to repair the damage suffered.ConclusionsOur findings clearly demonstrate that A. aurita can cause severe gill problems in marine-farmed fish. With aquaculture predicted to expand worldwide and evidence suggesting that jellyfish populations are increasing in some areas, this threat to aquaculture is of rising concern as significant losses due to jellyfish could be expected to increase in the future.

Consequences of Stinging Plankton Blooms on Finfish Mariculture in the Mediterranean Sea

“…For example, in April 2014 in Almería and May 2014 in the Málaga fish farm, gill scores were 6 ± 1.10 and 9.20 ± 0.60, respectively, and jellyfish occurred in medium-high densities (19.71 ± 3.07 ind m −3 in the Almería pen and 48.80 ± 10.79 ind m −3 in the Málaga facility) but no fish mortalities were reported in these periods. Experimental studies with the scyphozoan A. aurita showed gill epithelium recovery required 2 weeks after even brief (10 h) contact between jellyfish and salmonids (Baxter et al, 2011b). Equally, laboratory experiments carried out by Bosch-Belmar et al (2016b), demonstrated partial recovery of sea bream gill tissue after 3 weeks from fish exposure to medium densities of P. noctiluca.…”

“…Tiny and almost transparent medusae, siphonophores, and hydrozoan larvae may easily remain unnoticed to aquaculture operators, but they can develop high density blooms, be inhaled by fish, and inflict severe damage due to nematocyst discharge and consequent tissues envenomation (Fosså et al, 2003). A range of morphological injuries caused by contacts with cnidarian stinging cells have been described on several cultured fish species (Baxter et al, 2011b;Bosch-Belmar et al, 2016b;Marcos-López et al, 2016). Available evidence shows that a few hours of exposure to stinging cells may lead to severe damage at cellular, tissue and systemic levels, including changes in fish metabolic performances (BoschBelmar et al, 2016a).…”

Massive salp outbreaks in the inner sea of Chiloe Island (Southern Chile): possible causes and ecological consequences

“…However, the effect of man-made barriers is less well documented (Purcell et al, 2007;Doyle et al, 2008;Baxter et al, 2011;Mianzan et al, 2014). The ISCh possess the majority of the country's salmon farms with over 500 fish farms along the ISCh coast (excluding fjords) (Fig.…”

Is it possible to determine the economic impact of jellyfish outbreaks on fisheries? A Case Study – Slovenia

“…Jellyfish blooms have been shown to impact marine food webs (Malej et al, 2007) including the microbial loop (Tinta et al, 2012), limiting food for fish through competition (Pucell & Arai, 2001), harming farmed fish (Baxter et al, 2011), and exacerbating eutrophication phenomena (West et al, 2009). Although jellyfish abundance typically exhibits large inter-annual and decadal fluctuations (Condon et al, 2013), some recent studies have convincingly shown that several anthropogenically mediated factors stimulate the proliferation of jellyfish (Richardson et al, 2009;Purcell, 2012).…”