Final Evaluation Memorandum: Strategies for Resolving Low Dissolved Oxygen and Methylmercury Events in Northern Suisun Marsh

The purpose of the project is to improve our understanding about best management practices that can be utilized on diked managed wetlands in Suisun Marsh for reducing the occurrence of low dissolved oxygen (DO) and high methylmercury (MeHg) events associated primarily with fall flood-up practices. Low DO events are of concern because they can lead to undue stress and even mortality of sensitive aquatic organisms. Elevated MeHg levels are of concern because MeHg is a neurotoxin that bio-magnifies up the food chain and can cause deleterious effects to higher trophic level consumers such as piscivorous fish, birds, and mammals (including humans). This study involved two years (2007-2008) of intensive field data collection at two managed wetland sites in northwest Suisun Marsh and their surrounding tidal sloughs, an area with prior documented low DO events. In addition, the study collected limited soils and water quality field data and mapped vegetation for three managed wetland sites in the central interior of Suisun Marsh, for the purpose of examining whether wetlands at other locations exhibit characteristics that could indicate potential for similar concerns. In Year 1 of the study, the objective was to identify the baseline conditions in the managed wetlands and determine which physical management conditions could be modified for Year 2 to reduce low DO and MeHg production issues most effectively. The objective of Year 2 was to evaluate the effectiveness of these modified management actions at reducing production of low DO and elevated MeHg conditions within the managed wetlands and to continue improving understanding of the underlying biogeochemical processes at play. This Final Evaluation Memorandum examined a total of 19 BMPs, 14 involving modified water management operations and the remaining five involving modified soil and vegetation management practices. Some of these BMPs were previously employed and others have not yet been tested. For each BMP this report assesses its efficacy in improving water quality conditions and potential conflicts with wetland management. It makes recommendations for further study (either feasibility assessments or field testing) and whether to consider for future use. Certain previously used BMPs were found to be important contributors to poor water quality conditions and their continued use is not recommended. Some BMPs that could improve water quality conditions appear difficult to implement in regards to compatibility with wetland management; these BMPs require further elaboration and feasibility assessment to determine whether they should be field tested. In practice for any given wetland, there is likely a combination of BMPs that would together have the greatest potential to address the low DO and high MeHg water quality concerns. Consequently, this report makes no sweeping recommendations applicable to large groups of wetlands but instead promotes a careful consideration of factors at each wetland or small groups of wetlands and from that assessment to apply the most effective suite of BMPs. This report also identifies a number of recommended future actions and studies. These recommendations are geared toward improving the process understanding of factors that promote low DO and high MeHg conditions, the extent of these problems in Suisun Marsh, the regulatory basis for the DO standards for a large estuarine marsh, the economics of BMPs, and alternative approaches to BMPs on diked managed wetlands that may address the water quality issues. The most important of these recommendations is that future BMP implementation should be carried out within the context of rigorous scientific evaluation so as to gain the maximum improvement in how to manage these water quality issues in the diked managed wetlands of Suisun Marsh.

Influence of ocean conditions on the timing of early life history events for blue rockfish (Sebastes mystinus) off California

Settled juvenile blue rockfish (Sebastes mystinus) were collected from two kelp beds approximately 335 km apart off Mendocino in northern California and Monterey in central California. A total of 112 rockfish were collected from both sites over 5 years (1993, 1994, 2001, 2002, and 2003). Total age, settlement date, age at settlement, and birth date were determined from otolith microstructure. Fish off Mendocino settled mostly in June and fish off Monterey settled mostly in May (average difference in settlement=23 days). Although the difference in the timing of settlement followed this same pattern for both areas over the five years, settlement occurred later in 2002 and 2003 than in the prior years of sampling. The difference in the timing of settlement was due primarily to differences in birth dates for the two areas. The time of settlement was positively related to upwelling and negatively related to sea level anomaly for most of the months before settlement. Knowledge of the timing of settlement has implications for design and placement of marine protected areas because protection of nursery grounds is frequently a major objective of these protected areas. The timing of settlement is also an important consideration in the planning of surveys of early recruits because mistimed surveys (caused by latitudinal differences in the timing of settlement) could produce biased estimates.

Dietary variations in three co-occurring rockfish species off the Pacific Northwest during anomalous oceanographic events in 1998 and 1999

Stomach samples from three rockfish species, yellowtail (Sebastes f lavidus), widow (S. entomelas), and canary (S. pinniger) rockfish, seasonally collected off the Pacific Northwest in 1998 and 1999, provided quantitative information on the food habits of these species during and after the 1997–98 El Niño event. Although euphausiids were the most common major prey of all three predators, gelatinous zooplankton and fishes were the most commonly consumed prey items during some seasonal quarters. The influence of the El Niño event was evident in the diets. Anomalous prey items, including the southern euphausiid species Nyctiphanes simplex and juveniles of Pacific whiting (Merluccius productus) frequently appeared in the diets in the spring and summer of 1998. The results of stomach contents analyses, based on 905 stomach samples from 49 trawl hauls during seven commercial fishing trips and from 56 stations during research surveys, were consistent with the timing of occurrence and the magnitude of change in biomass of some zooplankton species reported from zooplankton studies in the northern California Current during the 1997–98 El Niño. Our findings indicate that the observed variations of prey groups in some rockfish diets may be a function of prey variability related to climate and environment changes.

Evaluating methods for estimating rare events with zero-heavy data: a simulation model estimating sea turtle bycatch in the pelagic longline fishery

Estimating rare events from zero-heavy data (data with many zero values) is a common challenge in fisheries science and ecology. For example, loggerhead sea turtles (Caretta caretta) and leatherback sea turtles (Dermochelys coriacea) account for less than 1% of total catch in the U.S. Atlantic pelagic longline fishery. Nevertheless, the Southeast Fisheries Science Center (SEFSC) of the National Marine Fisheries Service (NMFS) is charged with assessing the effect of this fishery on these federally protected species. Annual estimates of loggerhead and leatherback bycatch in a fishery can affect fishery management and species conservation decisions. However, current estimates have wide confidence intervals, and their accuracy is unknown. We evaluate 3 estimation methods, each at 2 spatiotemporal scales, in simulations of 5 spatial scenarios representing incidental capture of sea turtles by the U.S. Atlantic pelagic longline fishery. The delta-log normal method of estimating bycatch for calendar quarter and fishing area strata was the least biased estimation method in the spatial scenarios believed to be most realistic. This result supports the current estimation procedure used by the SEFSC.

Ancient DNA from South-East Europe Reveals Different Events during Early and Middle Neolithic Influencing the European Genetic Heritage

The importance of the process of Neolithization for the genetic make-up of European populations has been hotly debated, with shifting hypotheses from a demic diffusion (DD) to a cultural diffusion (CD) model. In this regard, ancient DNA data from the Balkan Peninsula, which is an important source of information to assess the process of Neolithization in Europe, is however missing. In the present study we show genetic information on ancient populations of the South-East of Europe. We assessed mtDNA from ten sites from the current territory of Romania, spanning a time-period from the Early Neolithic to the Late Bronze Age. mtDNA data from Early Neolithic farmers of the Starcevo Cris culture in Romania (Carcea, Gura Baciului and Negrilesti sites), confirm their genetic relationship with those of the LBK culture (Linienbandkeramik Kultur) in Central Europe, and they show little genetic continuity with modern European populations. On the other hand, populations of the Middle-Late Neolithic (Boian, Zau and Gumelnita cultures), supposedly a second wave of Neolithic migration from Anatolia, had a much stronger effect on the genetic heritage of the European populations. In contrast, we find a smaller contribution of Late Bronze Age migrations to the genetic composition of Europeans. Based on these findings, we propose that permeation of mtDNA lineages from a second wave of Middle-Late Neolithic migration from North-West Anatolia into the Balkan Peninsula and Central Europe represent an important contribution to the genetic shift between Early and Late Neolithic populations in Europe, and consequently to the genetic make-up of modern European populations.

Variation in yellowfin tuna (Thunnus albacares) catches related to El Niño-Southern Oscillation events at the entrance to the Gulf of California

Fishery catch data on yellowfin tuna (Thunnus albacares) were examined to study the effects of El Niño events between 1990 and 1999 for an area in the northeastern tropical Pacific (18−24°N, 112−104°W). The data were extracted from a database of logbook records from the Mexican tuna purse-seine f leet. Latitudinal distribution of the catches increased from south to north for the 10-year period. Highest catches and effort were concentrated between 22°N and 23°N. This area accumulated 48% of the total catch over the 10year period. It was strongly correlated with El Niño-Southern Oscillation (ENSO) events. At least two periods of exceptionally high catches occurred following El Niño events in 1991 and 1997. Peaks of catches were triggered by the arrival of positive anomalies of sea surface temperature (SST) to the area. A delay of two to four months was observed between the occurrence of maximum SST anomalies at the equator and peaks of catch. Prior to these two events, negative SST anomalies were the dominant feature in the study area and catch was extremely low. This trend of negative SST anomalies with low catches followed by positive SST anomalies and high catches may be attributed to northward yellowfin tuna migration patterns driven by El Niño forcing, a result that contrasts with the known behavior of decreasing relative abundance of these tuna after El Niño events in the eastern Pacific. However, this decrease in relative abundance may be the result of a local or subregional effect.

Effects of El Niño events on energy demand and egg production of rockfish (Scorpaenidae: Sebastes): a bioenergetics approach

Fish bioenergetics models estimate relationships between energy budgets and environmental and physiological variables. This study presents a generic rockfish (Sebastes) bioenergetics model and estimates energy consumption by northern California blue rockf ish (S. mystinus) under average (baseline) and El Niño conditions. Compared to males, female S. mystinus required more energy because they were larger and had greater reproductive costs. When El Niño conditions (warmer temperatures; lower growth, condition, and fecundity) were experienced every 3−7 years, energy consumption decreased on an individual and a per-recruit basis in relation to baseline conditions, but the decrease was minor (<4% at the individual scale, <7% at the per-recruit scale) compared to decreases in female egg production (12−19% at the individual scale, 15−23% at the per-recruit scale). When mortality in per-recruit models was increased by adding fishing, energy consumption in El Niño models grew more similar to that seen in the baseline model. However, egg production decreased significantly — an effect exacerbated by the frequency of El Niño events. Sensitivity analyses showed that energy consumption estimates were most sensitive to respiration parameters, energy density, and female fecundity, and that estimated consumption increased as parameter uncertainty increased. This model provides a means of understanding rockfish trophic ecology in the context of community structure and environmental change by synthesizing metabolic, demographic, and environmental information. Future research should focus on acquiring such information so that models like the bioenergetics model can be used to estimate the effect of climate change, community shifts, and different harvesting strategies on rockfish energy demands.

Northerly Distribution of White Sharks, Carcharodon carcharias, in the Eastern Pacific and Relation to ENSO Events

Twenty-nine verified records of white sharks, Carcharodon carcharias, from British Columbia and Alaska waters (1961–2004) are presented. Record locations ranged from lat. 48°48ʹN to lat. 60°17ʹN, including the northernmost occurrence of a white shark and the first report of this species from the central Bering Sea. White sharks recorded from the study area were generally large, with 95% falling between 3.8 and 5.4 m in length. Mature white sharks of both sexes occur in British Columbia and Alaska waters, although they do not necessarily reproduce there. White sharks actively feed in the study area; their diet is similar to that reported for this species from Washington and northern California waters. Sea surface temperature (SST) concurrent with white shark records from the study area ranged from 16°C to between 6.4°C and 5.0°C, extending the lower extreme of the range of SST from which this species has been previously reported. White shark strandings are rarely reported, yet 16 (55%) of the records in this study are of beached animals; strandings generally occurred later in the year and at lower latitudes than nonstrandings. No significant correlation was found between white shark records in the study area and El Niño events and no records occurred during La Niña events. The data presented here indicate that white sharks are more abundant in the cold waters of British Columbia and Alaska than previous records suggest.

Sea Turtle Observations at Explosive Removals of Energy Structures

Observers were placed at offshore sites to monitor and protect sea turtles during explosive removals of oil and gas structures in the Gulf of Mexico off Louisiana and Texas. Data collected during more than 6,500 hours of monitoring at 106 structure removals in 1992 provided information on sea turtle distribution. Eighteen individuals were observed including 10 loggerheads, 2 leatherbacks, 1 hawksbill, and 5 unidentified sea turtles. The observation rate (individuals per monitoring hour) of sea turtles was about 30 times higher during aerial surveys than during day or night suiface surveys.