Papers by Konstantine J Rountos
Marine Pollution Bulletin
global contribution of forage fish to marine fisheries and ecosystems
Frontiers in Marine Science, 2021
This study assessed the diet of Summer flounder (SF,Paralichthys dentatus) in Shinnecock Bay, NY.... more This study assessed the diet of Summer flounder (SF,Paralichthys dentatus) in Shinnecock Bay, NY. Summer flounder are a recreationally and commercially important marine flatfish species found along the Eastern United States coastline. Despite their importance, few studies have examined the trophodynamics of a broad size spectrum of this species. Diet composition of summer flounder (n= 88) was assessed from 2014 to 2016 throughout Shinnecock Bay, a eutrophic bar-built estuary in New York. Species consumed and diet species richness differed significantly amongst SF size classes, with large [≥375 mm total length (TL)] and medium (>225: <375 mm) summer flounder showing higher levels of piscivory and more diverse diets than small-sized (≤225 mm) conspecifics. As voracious plastic predators, trends in annual and monthly diet variation generally followed prey availability in Shinnecock Bay. One exception to this general pattern occurred for winter flounder (Pseudopleuronectes america...
Journal of Great Lakes Research, 2018
Hydrological regimes are key drivers of productivity and structure in freshwater ecosystems but a... more Hydrological regimes are key drivers of productivity and structure in freshwater ecosystems but are increasingly impacted by human activity. Using 17 published food web models of 13 African lakes as a case study, we explored relationships between seasonal and interannual water level fluctuations and 15 attributes related to ecosystem function. We interpreted our results in the context of Odum's ecosystem maturity hypothesis, as systems with higher magnitude fluctuations may be kept at an earlier maturity stage than those that are relatively stable. The data we compiled indicate that long-term changes in the hydrological regimes of African lakes have already taken place. We used Least Absolute Shrinkage and Selection Operator (LASSO) regression to examine relationships between ecosystem attributes and seven physical characteristics. Of these characteristics, interannual water level fluctuation magnitude was the most frequently retained predictor in the regression models. Our results indicate that interannual water level fluctuations are positively correlated with primary and overall production, but negatively correlated with fish diversity, transfer efficiency, and food chain length. These trends are opposite those expected with increasing ecosystem maturity. Interestingly, we found seasonal water level fluctuations to be positively correlated with biomass. An increase in standing biomass is generally associated with more mature ecosystems. However, we found that less production and biomass occurred at high trophic levels in highly fluctuating compared to relatively stable systems. This synthesis provides evidence that water level fluctuations are a key process influencing ecosystem structure and function in lakes.
Ecohydrology, 2016
Hydrological regimes are significant drivers of fisheries production in many African Lakes due to... more Hydrological regimes are significant drivers of fisheries production in many African Lakes due to their influence on fish habitat and food availability, breeding success, and catchability. Lake Turkana, Kenya, will undergo substantial changes in hydrology due to water regulation and extraction along the Omo River in neighboring Ethiopia, which provides over 90% of its water. The objective of this study was to predict how the lake's fisheries, which provide an important livelihood and protein source in the region, will respond to hydrological change. While variations in fishing effort are poor predictors of fisheries catch in the lake, water levels and their fluctuations strongly influence fisheries production. Seasonal oscillations play a particularly important role, and with complete loss of these oscillations, the lake's predicted fisheries yield will decrease by over two thirds. The fishery is predicted to collapse at a lake level decline of 25 m, regardless of seasonal amplitude magnitude. The lake's total littoral habitat, where fisheries are currently concentrated, will increase in surface area with lake level declines of <25 m. However, the extent of productive, dynamic littoral habitat will decrease with dampening of the lake's seasonal oscillations. The most severe habitat loss will occur in the lake's Turkwel Sector, which hosts the region's highest human population densities, and North Sector, where inter‐tribal conflict over resources is common and likely to be exacerbated by lake level decline. The continued ecological functioning of Lake Turkana necessitates immediate efforts to develop and apply a water resource management plan rooted in science.
Aquaculture Environment Interactions, 2012
Marine Ecology Progress Series, 2014
Harmful algal blooms (HABs) caused by the dinoflagellate Cochlodinium polykrikoides have increase... more Harmful algal blooms (HABs) caused by the dinoflagellate Cochlodinium polykrikoides have increased in geographic extent, frequency, and duration in coastal areas worldwide. These blooms have negatively impacted many coastal fisheries, causing mass mortalities of both wild and farmed fish. Forage fish species may be particularly susceptible to HABs as they feed on plankton and are highly abundant in coastal ecosystems where these blooms occur. While mortalities associated with HABs have been well documented for juvenile and adult fish, the potential impacts to early life stages (i.e. embryos and eleutheroembryos) have not been explored. We conducted a series of toxicity experiments using a clonal laboratory culture of C. polykrikoides and 3 forage fish species (Atlantic silverside Menidia menidia, inland silverside M. beryllina, and sheepshead minnow Cyprinodon variegatus) all common on the US East Coast. Our experiments demonstrated that C. polykrikoides caused mortalities in both embryos and eleutheroembryos, but that sensitivity to acute toxicity differed among fish species (M. beryllina > M. menidia > C. variegatus) and among life stages (eleutheroembryos > embryos). Although embryos were somewhat resistant to C. polykrikoides biotoxins until they hatched, once they hatched, they experienced rapid mortality and impaired swimming ability. By testing ecologically relevant exposure times to C. polykrikoides, we found that eleutheroembryos can become incapacitated relatively quickly (i.e. within hours), and that surviving fish could recover swimming ability following removal from C. polykrikoides exposure. This research provides the first evidence of sublethal impacts on fish exposed to C. polykrikoides, and advances understanding of the potential ecosystem impacts of this harmful alga.
Stony Brook University Libraries. SBU Graduate School in Marine and Atmospheric Sciences. Lawrenc... more Stony Brook University Libraries. SBU Graduate School in Marine and Atmospheric Sciences. Lawrence Martin (Dean of Graduate School), Dr. Bradley J. Peterson, Thesis Advisor Assistant Professor Marine Sciences Research Center, Dr. Robert C. Aller, Thesis Reader Distinguished Professor Marine Sciences Research Center, Dr. Christopher J. Gobler, Thesis Reader Associate Professor Marine Sciences Research Center.
Marine Environmental Research
Marine Environmental Research
Transactions of the American Fisheries Society
ABSTRACT Forage fish play a pivotal role in marine ecosystems and economies worldwide by sustaini... more ABSTRACT Forage fish play a pivotal role in marine ecosystems and economies worldwide by sustaining many predators and fisheries directly and indirectly. We estimated the global forage fish contributions to marine ecosystems through a synthesis of 72 published Ecopath models from around the world. Three distinct contributions of forage fish were examined: 1) the support service of forage fish to predators in marine ecosystems, 2) the total catch and value of forage fisheries, and 3) the support service of forage fish to the catch and value of other commercially targeted predators. Forage fish use and value varied by latitude and ecosystem type, and exhibited patterns across these groups. Forage fish supported many kinds of predators, including fish, seabirds, marine mammals and squid. Predators with diets consisting of more than 50% forage fish were found in 70% of the models while 28% had at least one predator whose diet exceeded 75% forage fish. Overall, forage fish contribute a total of about $16.9 billion USD to global fisheries values annually, i.e. 20% of the global ex-vessel catch values of all marine fisheries combined. While the global catch value of forage fisheries was $5.6 billion, fisheries supported by forage fish were more than twice as valuable ($11.3 billion). These estimates provide important information for evaluating the trade-offs of various uses of forage fish across ecosystem types, latitudes, and globally. Although we did not estimate a monetary value for supportive contributions unrelated to fisheries, these could add substantially to the global value of forage fishes.
Fisheries, 2015
Abstract: The mean trophic level of fisheries catch is commonly used to describe and assess tempo... more Abstract: The mean trophic level of fisheries catch is commonly used to describe and assess temporal trends in fisheries. Though its value as an indicator to evaluate the relative health of fisheries in marine ecosystems has been hotly debated, the metric calculated is clear. We applied this indicator along with a relatively new indicator, the mean trophic level of predator consumption, to 40 Ecopath models around the world. Together, these measures were used to detect where fisheries and marine predators may be targeting similar trophic levels of prey. Globally, the mean trophic levels caught by all fisheries and finfish fisheries were similar to those consumed by marine mammals but significantly higher than those consumed by seabirds and large predatory fish. We found no significant differences between the median trophic levels targeted by forage fisheries and predators. These indicators can inform ecosystembased management, especially when information on predators and fishery interactions are limited or unavailable. El nivel trófico promedio de las capturas pesqueras se utiliza comúnmente para describir y evaluar las tendencias de las pesquerías a través del tiempo. Si bien su utilidad como indicador de la salud relativa de las pesquerías en ecosistemas marinos ha sido un tema de intenso debate, el cálculo de esta métrica es claro. En el presente artículo se aplicó este indicador junto con uno nuevo, el nivel trófico promedio del consumo de los depredadores, a 40 modelos Ecopath alrededor del mundo. Juntas, estas dos medidas fueron utilizadas para detectar dónde las pesquerías y los depredadores marinos pueden estar incidiendo en niveles tróficos similares de las presas. De forma global, los niveles tróficos promedio capturados por todas las pesquerías de escama fueron similares a aquellos consumidos por mamíferos marinos, pero sensiblemente más altos que aquellos consumidos por aves marinas y grandes peces depredadores. No se encontraron diferencias significativas entre los niveles tróficos que utilizan las pesquerías de peces forrajeros y los depredadores. Estos indicadores pueden aportar información útil para el manejo de las pesquerías basado en el ecosistema, especialmente cuando la información sobre los depredadores y las interacciones con las pesquerías es limitada o no está disponible.
Harmful algal blooms (HABs) caused by the dinoflagellate, Cochlodinium polykrikoides, have increa... more Harmful algal blooms (HABs) caused by the dinoflagellate, Cochlodinium polykrikoides, have increased in geographic extent, frequency, and duration in many coastal areas worldwide. These blooms have negatively impacted many coastal fisheries, causing mass mortalities to both wild and farmed fish. While these mortalities have been well documented for juvenile and adult fish, the potential impacts to early life stages (i.e. embryos and eleutheroembryos) have not been explored. The potential toxicity of HABs on early life stages could significantly affect recruitment in coastal fish populations. To address this critical research gap, we conducted a series of toxicity experiments using clonal cultures of C. polykrikoides and early life stages of three forage fish species (Menidia menidia, Menidia beryllina, and Cyprinodon variegatus), all common in Northeast U.S. estuaries. We present the impacts of C. polykrikoides on embryo survival and hatching success as well as the survival of newly...
The mean trophic level of fisheries catch (mTLY) is commonly used as an index to evaluate the sta... more The mean trophic level of fisheries catch (mTLY) is commonly used as an index to evaluate the state of fisheries in ecosystems. Here, it was used simply to estimate the mean trophic level of catches for 1) all fisheries, 2) all finfish fisheries, and 3) all forage fisheries. In a similar manner, the mean trophic level of predator consumption (mTLq) index was used to estimate the trophic level of prey items that marine predators were consuming in a given ecosystem. These indices were used in order to screen for potential ecosystems or latitude groups where fisheries and the major predator categories (i.e. seabirds, marine mammals, and large predatory fish) may be targeting prey at similar trophic levels. We utilized 43 marine ecosystem models (Ecopath) from an existing database and from other sources, which represented ecosystems within the last 40 years and included all the major predators groups. Few differences were found between the mean trophic levels targeted by fisheries and p...
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Papers by Konstantine J Rountos