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September 2013

First Quantitative Comparison of Atlantic Bluefin Tuna Spawning Grounds

First Quantitative Comparison of Atlantic Bluefin Tuna Spawning Grounds

Using satellite data, shipboard plankton surveys and in situ data, U.S. and Spanish scientists have provided the first quantitative comparison of the environmental characteristics of the only two known spawning habitats of Atlantic bluefin tuna (Thunnus thynnus). Collaborators included academic (the Cooperative Institute for Marine and Atmospheric Studies and Oregon State University), government (National Marine Fisheries Service and the Spanish Institute for Oceanography) and private industry (Roffers Ocean Fishing Forecasting) scientists.  Results from their collaborative study were published in Marine Ecology Progress Series.  

Background: Bluefin tuna in the north Atlantic are divided into two stocks: a western stock, which spawns in the Gulf of Mexico, and an eastern stock, which spawns in the Mediterranean Sea. Using larval catches from plankton surveys, and environmental variables from in situ measurements and remotely sensed satellite data, the characteristics of the two spawning habitats were compared.   Results highlighted the importance of warm (23-28°C), low chlorophyll areas with moderate current velocities.  Bluefin tuna spawning in the Gulf of Mexico do so in offshore waters just outside of the Loop Current, while in the western Mediterranean, they spawn at a confluence of inflowing Atlantic waters and saltier resident Mediterranean surface water. 

Significance: Atlantic bluefin tuna stocks are at historically low levels, and both eastern and western stocks are currently managed under stock rebuilding plans.  Simply limiting catch may not be sufficient for stocks to recover. A quantitative assessment of the characteristics of the natural spawning habitats is essential to understand the actual constraints upon larval growth, larval survival, and ultimately recruitment into the fishery. This research project was undertaken and funded in support of the National Oceanic and Atmospheric Administration mission goal to sustain marine fisheries and fisheries habitats within healthy oceans.

Contact Information: Barbara Muhling, bmuhling@rsmas.miami.edu

Summary

Using satellite data, shipboard plankton surveys and in situ data, U.S. and Spanish scientists have provided the first quantitative comparison of the environmental characteristics of the only two known spawning habitats of Atlantic bluefin tuna (Thunnus thynnus).

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Safer Great Lakes Swimming Beaches – CILER Research in Action

Safer Great Lakes Swimming Beaches – CILER Research in Action

The most common method for managing beaches, referred to as the “persistence model”, assumes that fecal indicator bacteria (FIB) concentrations, such as E. coli, from yesterday are representative of today, due to the 24-hour time requirement for analyzing FIB.  The assumption of using day old data for managing public beaches may result in over-conservative or under-conservative beach advisories. For several years, beach managers in the Great Lakes have expressed interest in predictive beach water quality tools that will help them better manage beaches.

Researchers at the Cooperative Institute for Limnology and Ecosystems Research (CILER) are collaborating with NOAA’s Great Lakes Environmental Research Laboratory (GLERL) and NOAA’s Center of Excellence for Great Lakes and Human Health (CEGLHH) to develop a beach water quality forecasting system. The system links watershed land use and runoff from precipitation, forecasts of river discharge and near-shore currents, and biological processes to predict and simulate concentrations of fecal indicator bacteria at beaches impacted by river discharge using GLERL’s Huron-Erie Connecting Waterways Forecasting System (HECWFS). Nearly two seasons of intensive monitoring have been completed for the beaches impacted by the Michigan’s Clinton River, and provide the basis for this decision support tool.

In addition to providing a new tool for determining safety of Great Lakes beaches, this program represents a major contribution to near-shore ecological forecasting by demonstrating the use of linked models to simulate pollutant fate and transport. This work supports CEGLHH’s goal of understanding of ecosystem processes, particularly hydrodynamics and the influence of abiotic factors on the fate, transport of sources and loadings of bacteria and microbial contaminants to assist in environmental decision-making and reduce human health risks.

Contact Information: Lauren Fry, CILER Research Fellow

Summary

Researchers at the Cooperative Institute for Limnology and Ecosystems Research (CILER) are collaborating with NOAA’s Great Lakes Environmental Research Laboratory (GLERL) and NOAA’s Center of Excellence for Great Lakes and Human Health (CEGLHH) to develop a beach water quality forecasting system.

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