Jellyfish, Forage Fish, and the World's Major Fisheries

Abstract

A majority of the world's largest net-based fisheries target planktivorous forage fish that serve as a critical trophic link between the plankton and upper-level consumers such as large predatory fishes, seabirds, and marine mammals. Because the plankton production that drives forage fish also drives jellyfish production, these taxa often overlap in space, time, and diet in coastal ecosystems. This overlap likely leads to predatory and competitive interactions, as jellyfish are effective predators of fish early life stages and zooplankton. The trophic interplay between these groups is made more complex by the harvest of forage fish, which presumably releases jellyfish from competition and is hypothesized to lead to an increase in their production. To understand the role forage fish and jellyfish play as alternate energy transfer pathways in coastal ecosystems, we explore how functional group productivity is altered in three oceanographically distinct ecosystems when jellyfish are abundant and when fish harvest rates are reduced using ecosystem modeling. We propose that ecosystem-based fishery management approaches to forage fish stocks include the use of jellyfish as an independent, empirical "ecosystem health" indicator. DEDICATION. This paper is dedicated to our beloved friend and colleague, Hermes Mianzan, for his innumerable contributions to fisheries, zooplankton, and gelatinous zooplankton ecology.

The global susceptibility of coastal forage fish to competition by large jellyfish

“…Thus, forage fish may be subject to tighter trophic control than jellyfish and are often targets of important commercial fisheries [3]. Food web structure, exploitation and feeding ecology may thus cause jellyfish to be dominant in pelagic ecosystems heavily affected by eutrophication, high water turbidity and fishing, as it has been suggested by other modelling studies [23,27].…”

“…They also have more indirect impacts on ecosystem functioning, as certain jellyfish and forage fish (small pelagic zooplanktivorous fish) feed at a similar trophic level [4][5][6]8,10,11]. Additionally, many jellyfish can be locally important predators on the younger life stages of fish [3,12]. Competition is notoriously difficult to prove [12] but environmentally induced changes in the ability of jellyfish to compete with fish are likely a cause of jellyfish proliferation and can have large negative impacts on both ecology and economy.…”

Associations between lobster phyllosoma and gelatinous zooplankton in relation to oceanographic properties in the northern Gulf of Mexico

“…Jellies are abundant and have a large impact on trophic interactions and carbon cycling (Greer et al., ; Sweetman, Smith, Dale, & Jones, ); however, their life histories and interactions with other organisms remain poorly described, partially due to the destructive nature of traditional plankton net sampling (Hamner et al., ; Remsen, Hopkins, & Samson, ). Although jellies are unpalatable for many zooplanktivores (Bullard & Hay, ), they have a suite of specialized or opportunistic predators, such as sea turtles and several fish species (Arai, ; D'Ambra, Graham, Carmichael, & Hernandez, ; Mianzan, Pájaro, Alvarez Colombo, & Madirolas, ), and can serve as alternative pathways for carbon cycling in marine food webs (Robinson et al., ). Some gelatinous zooplankton contain portions of their bodies that are high in carbon content and could be preferentially eaten by predators (Milisenda et al., ; Shenker, ).…”

ITAG: an eco-sensor for fine-scale behavioral measurements of soft-bodied marine invertebrates

“…They are broadly distributed and often centrally located within food webs as predators and prey to a wide array of taxa across multiple trophic levels [1,2]. Occasionally cited as keystone taxa, some squid and jellyfish species provide a crucial link between apex predators (e.g., marine mammals, turtles, sharks, tunas, billfish) and the invertebrates' smaller pelagic, mesopelagic and planktonic prey [3][4][5][6].…”