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

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.Fil: Robinson, Kelly L. State University of Oregon; Estados UnidosFil: Ruzicka, James J.. State University of Oregon; Estados UnidosFil: Decker, Mary Beth. University of Yale; Estados UnidosFil: Brodeur, RIchard. NOAA Northwest Fisheries Science Center; Estados UnidosFil: Hernandez, Frank. University Of Mississippi; Estados UnidosFil: Quiñones Dávila, Javier. Instituto del Mar del Perú; PerúFil: Acha, Eduardo Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; Argentina. Universidad Nacional de Mar del Plata; ArgentinaFil: Uye, Shin-ichi. Graduate School of Biosphere Science; JapónFil: Mianzan, Hermes Walter. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; Argentina. Universidad Nacional de Mar del Plata; ArgentinaFil: Graham, William M.. The University of Southern Mississippi; Estados Unido

Jellyfish, Forage Fish, and the World\u27s Major Fisheries

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

Questioning the rise of gelatinous zooplankton in the World's oceans

During the past several decades, high numbers of gelatinous zooplankton species have been reported in many estuarine and coastal ecosystems. Coupled with media-driven public perception, a paradigm has evolved in which the global ocean ecosystems are thought to be heading toward being dominated by “nuisance” jellyfish. We question this current paradigm by presenting a broad overview of gelatinous zooplankton in a historicalcontext to develop the hypothesis that population changes reflect the human-mediated alteration of global ocean ecosystems. To this end, we synthesize information related to the evolutionary context of contemporary gelatinous zooplankton blooms, the human frame of reference forchanges in gelatinous zooplankton populations, and whether sufficient data are available to have established the paradigm. We conclude that the current paradigm in which it is believed that there has been a global increase in gelatinous zooplankton is unsubstantiated, and we develop a strategy for addressing the critical questions about long-term, human-related changes in the sea as they relate to gelatinous zooplankton blooms

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

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

内湾性橈脚類Acartia clausiとA.steueriの発生 : II. 等時生長

Isochronal development is a general feature in stage succession of neritic copepods Acartia clausi and A. steueri, when they are cultured at optimal temperatures with excess food. However, stage duration of NI is shorter and of NII is compensatingly longer than the other later stages which are almost equal in time. The time required from egg-laying to reach any developmental stage at a given temperature can be calculated from the Bělehrádek equation by proper multiplication of proportional constant for embryonic development at that temperature. Isochronal development may be more advantageous than nonisochronal development for some species of the genus Acartia to ensure high reproductive potential of the population by reducing the mortality during copepodite stages

内湾性橈脚類Acartia clausiとA.steueriの発生 : I. 孵化に及ぼす環境要因の影響と休眠卵の性質

Effects of temperature, salinity-temperature combinations, illumination and the presence of bottom mud on the egg development of neritic copepods Acartia clausi and A. steueri were investigated. Since eggs of both species obtained from various months behaved similarly in haching at various temperatures and in survival during storage within the mud, the eggs of these copepods have the same physiological properties throughout the year (i.e. subitaneous eggs). Resting eggs accumulated within the natural sea-bottom mud are also subitaneous ones, which are merely inhibited from hatching by unfavorable environmental conditions (e.g. low temperature, low oxygen concentration, darkness). The time-release effect of hatching from resting eggs may act to enhance the maintenance of endemic copepod populations in highly variable environments

Pseudodiaptomus marinus(橈脚亜綱: カラヌス目)の各発育段階での天然懸濁粒子の摂食

Comparative grazing experiments of various developmental stages and sexes of the inshore marine copepod Pseudodiaptomus marinus on naturally occurring particles were carried out. The feeding behavior was similar between both sexes of the adult, but different between developmental stages. The adult females were capable of consuming almost all particles from 2.8 to 63.3 μm diameter, showing selectivity for larger particles (ca. 50 μm) where the peak of particle concentration occurred. The nauplii consumed mainly smaller particles (<30 μm). The consumption by copepodites was intermediate between that of the nauplii and adult females, since they fed upon both smaller and larger particles. Such intraspecific differences of grazing behavior may lead to the effective utilization of heterogeneous natural food resources. The ingestion rates of the adult females increased linearly with the increase of particle concentrations, without indications of the threshold nor saturation response. The amount of ingested carbon rarely met the requirement for potential egg production which was observed for the wild population. Thus, it was surmised that the adult females could ingest sufficient food deposited on the sea-bottom during a daytime epibenthic phase to attain predicted egg production