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Gulf menhaden (Brevoortia patronus) support the largest fishery by yield in the Gulf of Mexico (GoM) and are a key forage species for many marine predators. While menhaden stock assessments indicated that overfishing was not likely to have occurred in the past, concerns have been raised regarding the possible effects of menhaden fishing on their predators. In this study, we used a US Gulfwide Ecopath with Ecosim (EwE) model to explore the predicted effects of increased menhaden harvest on the GoM ecosystem and focused our analyses on Gulf menhaden predators. Key menhaden predators identified included king mackerel (Scomberomorus cavalla), Spanish mackerel (Scomberomorus maculatus), sea trout (Cynoscion spp.), red drum (Sciaenops ocellatus), and pelagic coastal piscivores [e.g., bluefish (Pomatomus saltatrix)]. As expected, these predators exhibited reduced biomass in response to increased Gulf menhaden harvest, with a predicted 11% decrease in predator biomass at simulated fishing levels near historical highs. Our results indicate strong relationships between the effects of menhaden fishing and the predator fishing mortality for king mackerel and intermediate relationships for Spanish mackerel, blacktip shark (Carcharhinus limbatus), red drum, large coastal sharks, and pelagic coastal piscivores. Biomass of predator groups such as demersal coastal invertebrate feeders [e.g., drums and croakers (Sciaenidae)] are more affected by menhaden harvest (through trophodynamics interactions and bycatch removal) compared to the isolated effect of their fishing mortality. For almost all the groups examined in the trade-off analysis, with the exception of sea trout, current biomass (2016) was higher than their target biomass representing 75% of their biomass at maximum sustainable yield. In comparison to the time series of fishing mortality rates estimated by the most recent Gulf menhaden stock assessment, the mean ecological reference point (ERP) of 0.862 was exceeded in all but 1 year from 1977 to 2007; however, neither the target nor threshold upper ERP value has been exceeded since 2008. The observed Gulf menhaden landings from 2003 to the present were generally within the range of the projected equilibrium landings (i.e., within confidence intervals) at both the ERP target and threshold values except for three recent years.

Estuaries present a set of unique challenges for freshwater fish. In addition to basic physiological challenges, the influx of salinity can affect prey availability and can influence resource consumption. Diets of coastal Largemouth Bass Micropterus salmoides were surveyed from three sites in the Mobile Bay estuary, Alabama, USA, from April 2011 to April 2015. A large proportion of Largemouth Bass consumed blue crabs Callinectes sapidus (proportion occurrence [PO] = 0.38) and mud crabs Panopeus spp. (PO = 0.24). Largemouth Bass also consumed grass shrimp Palaemonetes spp. (PO = 0.16), Gulf Menhaden Brevoortia patronus (PO = 0.14), and mysid shrimp Mysidopsis spp. (PO = 0.12). Prey diversity was greater at the lower estuary site (Fowl River) than at the sites in the upper estuary (Bay Minette and D'Olive Bay). A principal components analysis based on the biomass diet data revealed that invertebrates were the most important prey resource for coastal Largemouth Bass, with finfishes playing a secondary role. Seasonal inputs of estuarine fish species, such as Gulf Menhaden, represented an important prey resource in the diets of Largemouth Bass during both spring and summer. [ABSTRACT FROM AUTHOR]

We evaluated the effects of multiple bottom-up processes on the relative condition (an index of length-specific weight) of adult Gulf menhaden Brevoortia patronus sampled from the US commercial fishery, from 1964 to 2011, in the northern Gulf of Mexico (NGOM). A series of Generalized Additive Models (GAMs) were constructed to examine the influence of Mississippi River Discharge (MRD), El Niño Southern Oscillation (ENSO), wind vector components, sea surface temperature (SST), and chlorophyll a concentration. Relative condition was positively correlated with MRD and highest during weak La Nina-like and moderate El Nino-like conditions. The effect of wind vector components was variable across the NGOM. This observation is likely due to geographic differences in wind-related transport of nutrient rich river plume waters. Relative condition was highest at 24°C and declined rapidly when SST was below 23°C or above 29°C. Relative condition exhibited seasonal variability with increasing condition from August until November, likely caused by seasonal provisioning by individuals for winter spawning. We show that multiple bottom-up processes contribute to contrasts in the condition of Gulf menhaden in the NGOM and these results can be used to predict the response of Gulf menhaden to environmental variability. [ABSTRACT FROM AUTHOR]

Gulf Menhaden ( Brevoortia patronus ) are a species of commercial and ecological importance in the northern Gulf of Mexico, provisioning the second largest fishery by weight, in the United States, and providing critical ecosystem services in the coastal region. The recruitment and productivity dynamics of the stock are influenced by a suite of environmental factors but an understanding of the factors that determine individual variation in oil content (an indicator of an individual’s commercial value to the fishery and its dietary value to predators) has not been well described. In this work I describe the temporal dynamics of oil content and determine the demographic characteristics that provide predictive power to describe annual contrasts. I relate the predicted patterns in oil yield to a suite of seasonal environmental data series including: the magnitude of spring Mississippi River discharge, spring wind vectors, and the preceding winter El Nino conditions. Two uncorrelated (r = 0.06, p = 0.81) population-level predictor variables were identified that have explanatory power to describe temporal patterns in oil content (L kg −1 ); a weight-at-length power function parameter ( a ) and the von Bertalanffy asymptotic fork length ( L ∞ , mm FL): L kg −1 = − 0.158 − 0.026* a − 0.00163* L ∞ (p < 0.05, R 2 = 0.42). Analysis of the impacts of environmental variables on the oil content of Gulf Menhaden was evaluated comprehensively in a Bayesian framework by transforming the observed oil content information from two sources to a common scale. Parameters relating oil content to spring Mississippi River discharge and the preceding winter (December–February) El Nino Southern Oscillation index resulted in sample distributions from the posterior where zero was outside the 95% credible interval. This work contributes to the understanding of Gulf Menhaden as a prey species in the Gulf of Mexico and indicates that the value of the species to both the fishery and predators exhibits relatively large inter-annual variability controlled, in part, by seasonal environmental conditions. [ABSTRACT FROM AUTHOR]

Gulf menhaden (Brevoortia patronus) produce one of the largest U.S. fisheries, yet information on reproductive dynamics of the stock is sparse. Males and females reach 50% maturity at 140.8 and 137.2 mm fork length, respectively and recruit into the commercial fishery at this size. Analysis of fishery-dependent data from 1964 through 2014 indicated that somatic condition was lower during the late 1980s and late 2000s and that reproductively active fish from 2014 were significantly larger and had greater gonadosomatic index values than those from 1964 through 1970. Histological analysis performed on fish from 2014 through 2016 revealed spawning-capable and actively spawning fish of both sexes from early October through mid- March. Females have indeterminate fecundity, are batch spawners, and spawn every 2.1-4.3 days, although oocyte recruitment shows some characteristics of determinate fecundity. Mean relative batch fecundity was 107.8 eggs/g ovary-free body weight (standard error 17.1). Estimates from age-structured assessment models based on updated fecundity and maturity measures resulted in a 100-1000× greater production of eggs than previous estimates. Model output, including the number-at-age, age-specific fishing-induced mortality, and spawners-per-recruit are sensitive to alterations in age-specific annual fecundity. Therefore, updated estimates of Gulf menhaden reproductive dynamics can affect assessments of the stock. [ABSTRACT FROM AUTHOR]

Gulf menhaden ( Brevoortia patronus) exhibited unprecedented juvenile recruitment in 2010 during the year of the Deepwater Horizon well blowout, exceeding the prior 39-year mean by more than four standard deviations near the Mississippi River. Abundance of that cohort remained exceptionally high for two subsequent years as recruits moved into older age classes. Such changes in this dominant forage fish population can be most parsimoniously explained as consequences of release from predation. Contact with crude oil induced high mortality of piscivorous seabirds, bottlenose dolphin ( Tursiops truncatus), waders, and other fish-eating marsh birds, all of which are substantial consumers of Gulf menhaden. Diversions of fresh water from the Mississippi River to protect coastal marshes from oiling depressed salinities, impairing access to juvenile Gulf menhaden by aquatic predators that avoid low-salinity estuarine waters. These releases from predation led to an increase of Gulf menhaden biomass in 2011 to 2.4 million t, or more than twice the average biomass of 1.1 million t for the decade prior to 2010. Biomass increases of this magnitude in a major forage fish species suggest additional trophically linked effects at the population-, trophic-level and ecosystem scales, reflecting an heretofore little appreciated indirect effect that may be associated with major oil spills in highly productive marine waters. [ABSTRACT FROM AUTHOR]

Catchability relates fishing effort to fishing mortality, and is an important component in fishery stock assessment models. Mis-specifying catchability can lead to inaccurate estimation of model parameters and bias in the determination of stock status. The Gulf of Mexico has one of the largest seasonal occurrences of hypoxia in the world and it overlaps in time and space with the Gulf menhaden Brevoortia patronus fishery, potentially leading to temporal and spatial patterns in stock distribution and thus catchability. These patterns are not currently modeled in the Gulf menhaden stock assessment. To better understand the implications of spatial and temporal patterns in catchability due to hypoxia, we constructed an operating model of Gulf menhaden fishery dynamics under various assumptions of spatial coverages and temporal patterns, and used the output from the operating model as input into estimation models with alternative approaches on modeling catchability. Under the most extreme assumptions about the spatial coverage and magnitude of variation in catchability, median absolute error in estimates of fishing mortality and spawning stock reference points ( F 30% and S 30% ) was 73% and 29%, respectively, and median absolute error in estimates of fishing mortality and spawning stock based stock status was 23% and 79%, supporting the notion that errors in catchability are important. Under more reasonable assumptions, median absolute error declined to 20% and 2.9% for F 30% and S 30% , respectively, and to 3.8% and 2.4% for fishing mortality and spawning stock-based stock status, respectively. Modeling catchability as a random walk further reduced median absolute error to 5.0% for F 30% and 1.4% for S 30% , but slightly increased median absolute error for stock status indicators to 4.0% and 3.3%. Our results show generally that the spatial coverage, temporal pattern, and estimation approach of catchability affects the influence of mis-specifying catchability; and show specifically that the Gulf menhaden stock assessment is robust to the effects of hypoxia on catchability if assuming random-walk catchability. [ABSTRACT FROM AUTHOR]

Approximately 4.9 million barrels of crude oil and gas were released into the Gulf of Mexico (GoM) from April to July 2010 during the Deepwater Horizon (DWH) spill. This resulted in the possible contamination of marine organisms with polycyclic aromatic hydrocarbons (PAHs), USEPA identified constituents of concern. To determine the impact of the DWH oil spill, Gulf menhaden ( Brevoortia patronus ), a commercially harvested and significant trophic grazing species, was sampled from two Louisiana coastal regions between the years 2011–2013. Tissue extraction and GC/MS analysis demonstrated measurable concentrations of PAH within menhaden. Analysis yielded total PAHs, carcinogenic equivalents (BaP-TEQ), and mutagenic equivalents (BaP-MEQ) which provided an initial toxic potential assessment of this GoM Fishery. Gulf menhaden contained less total PAH concentrations in 2012 and significantly less in 2013 as compared to 2011 (p < 0.05) ranging from 7 ug/g tissue dry weight to 3 ng/g tissue dry weight. Carcinogenic and mutagenic PAHs were also significantly reduced (p < 0.05) over the three year period. The reduction of total PAH concentrations and the reduction of BaP-TEQs and MEQs between 2011 and 2013 indicates a diminished input of new source PAHs along with a reduction of carcinogenic and mutagenic PAHs in menhaden populations. The use of Gulf menhaden was successful in determining the acute toxic potential of PAHs contaminating the GoM in the years directly following the DWH spill event. [ABSTRACT FROM AUTHOR]

Histopathologic lesions were observed in the commercially important filter-feeding fish, Brevoortia patronus (Gulf menhaden), along the Louisiana Gulf Coast. Menhaden collected from Louisiana waters in 2011 and 2012, 1 and 2 years following the Deepwater Horizon oil spill, showed varying severities of gill lesions as well as an unusual accumulation of black particulates visible at necropsy in the heart and stomach vasculature. The PAH derived particulates were typically 1-4 µm in diameter, but larger aggregates were observed in the coronary vessels on the ventricle surfaces and their location and size was confirmed by light microscopy. Composited particulate composition was consistent with weathered petrogenic polycyclic aromatic hydrocarbon (PAH) mixtures based on GC-MS analysis. Particulates were present in 63 and 80 % of fish hearts and 70 and 89 % of stomach muscularis collected in 2011 and 2012, respectively. Tissue embedded particulates can lead to localized cellular damage from bioavailable compounds, as well as chronic effects from occlusion of sensitive tissues' blood flow. The PAH derived particulates appeared to act as emboli in small capillaries, and could associated with localized inflammation, focal necrosis and inappropriate collagen and fibroblast tissue repair. We believe large volume filter feeding teleosts, such as menhaden (up to 3 million gallons per year/fish) with high lipid content, have a higher exposure risk and greater potential for toxicity from toxic particulates than other higher trophic level finfish. Suspended PAH derived particulates following an oil spill therefore, should be considered when assessing long-term ecological impacts and not be limited to physical contact (coating) or water soluble fractions for assessing toxicity (gill and neurologic). [ABSTRACT FROM AUTHOR]

Fishery management production models tend to stress only the elements directly linked to fish (i.e. fish, fish food, and fish predators). Large coastal jellyfish are major consumers of plankton in heavily fished ecosystems; yet, they are frequently not included as model components. We explore the relationship between gulf menhaden (Brevoortia patronus) and the large scyphozoan jellyfish (Aurelia spp. and Chrysaora sp.), and provide an examination of trophic energy transfer pathways to higher trophic levels in the northern Gulf of Mexico. A trophic network model developed within the ECOPATH framework was transformed to an end-to-end model to map foodweb energy flows. Relative changes in functional group productivity to varying gulf menhaden consumption rates, jellyfish consumption rates, and forage fish (i.e. gulf menhaden, anchovies, and herrings) harvest rates were evaluated within a suite of static, alternative energy-demand scenarios using ECOTRAN techniques. Scenario analyses revealed forage fish harvest enhanced jellyfish productivity, which, in turn, depressed menhaden productivity. Modelled increases in forage fish harvest caused pronounced changes in ecosystem structure, affecting jellyfish, marine birds, piscivorous fish, and apex predators. Menhaden were found to be a more efficient and important energy transfer pathway to higher trophic levels compared with jellyfish. A simulated increase in jellyfish abundance caused the relative production of all model groups to decline. These outcomes suggest that jellyfish blooms and forage fish harvest have demonstrable effects on the structure of the northern Gulf of Mexico ecosystem. [ABSTRACT FROM AUTHOR]

Abundances of Gulf menhaden (Brevoortia patronus) in the northern Gulf of Mexico (GOM) are heavily influenced by physical and biological processes that affect refuge and food availability. This study identified specific decadal and interannual responses in the recruitment of Gulf menhaden to local meteorological and hydrological regimes imposed by the coupling of Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) phases and by El Niño Southern Oscillation (ENSO) events. Numbers of age-0 menhaden in fishery-independent surveys and numbers and proportions of Gulf menhaden ages 1-6 in commercial purse-seine landings in the northern GOM were used to investigate those responses. High postlarval abundance of Gulf menhaden (3.6/beam plankton haul) in the central region was related to the decadal wet regime associated with AMO cold and NAO positive phases. Elevated numbers of menhaden species (38.3/seine haul) in the western region were related to interannual wet regimes associated with ENSO warm and neutral events. High commercial landings of Gulf menhaden (10 million fish/vessel ton week) were related to the decadal average hydrological regime associated with AMO cold and NAO negative phases. Climate regimes may favor growth and survival by structuring offshore and inshore nursery habitats or by synchronizing release of larvae when offshore and inshore nursery conditions are favorable. [ABSTRACT FROM AUTHOR]

The Alabama River drainage is a biologically diverse system containing over 180 native fishes and at least 33 endemics. Many studies have surveyed single species of conservation concern, such as the federally endangered Scaphirhynchus suttkusi (Alabama Sturgeon), Alosa alabamae (Alabama Shad), and Crystallaria asprella (Crystal Darter), but few have documented entire fish assemblages. Maintaining fish-assemblage data is an important process in monitoring species and assemblage composition through time so that large-scale ecological change can be detected. In this study, we surveyed fish assemblages of sand/gravel bar habitat in the lower Alabama River and compared these data to those collected from historical surveys. Diel and seasonal surveys were conducted along 19 sandbars from Dixie Landing (river mile 22) to Claiborne Lock and Dam (river mile 72). We recorded a total of 48 species in 41 collections during summer, fall, and spring 2010-2011. Based on the Jaccard index, these samples had low similarity to historical samples collected by R.D. Suttkus and the Geological Survey of Alabama, suggesting temporal fish assemblage shifts. In 2010, we detected extremely high numbers of Brevoortia patronus (Gulf Menhaden) during summer and fall, which is a new distributional record. Diel comparisons using the Morisita index indicate low similarity reflecting large numbers of catfish species detected mostly in night collections. These data also indicate seasonal faunal changes among sandbar fish assemblages. Ongoing habitat alteration on the Alabama River is a potential factor leading to assemblage homogenization and potential loss of biodiversity. Future monitoring in the Alabama River should consider diel and seasonal sampling to accurately document fish species and assemblages, including potential shifts that may be occurring over space and time. [ABSTRACT FROM AUTHOR]

Long-term sustainable management of wild populations should be based on management actions that account for the genetic structure among populations. Knowledge of genetic structure and of the degree of demographic exchange between discreet populations allows managers to better define management units. However, adequate gene loci for population assessments are not always available. In this study, variable co-dominant DNA loci in the heavily exploited marine genus Brevoortia were developed with a microsatellite-enriched DNA library for the Gulf Menhaden (Brevoortia patronus). Microsatellite marker discovery was followed by genetic characterization of 4 endemic North American Brevoortia species, by using 14 novel loci as well as 5 previously described loci. Power analysis of these loci for use in species identification and genetic stock structure was used to assess their potential to improve the stock definition in the menhaden fishery of the Gulf of Mexico. These loci could be used to reliably identify menhaden species in the Gulf of Mexico with an estimated error rate of α=0.0001. Similarly, a power analysis completed on the basis of observed allele frequencies in Gulf Menhaden indicated that these markers can be used to detect very small levels of genetic divergence (Fst≈0.004) among simulated populations, with sample sizes as small as n=50 individuals. A cursory analysis of genetic structure among Gulf Menhaden sampled throughout the Gulf of Mexico indicated limited genetic structure among sampling locations, although the available sampling did not reach the target number (n=50) necessary to detect minimal values of significant structure. [ABSTRACT FROM AUTHOR]

A new adaptation based on matrix solid phase dispersion of tissue for the subsequent isolation of polycyclic aromatic hydrocarbons was developed and used for extractions of Gulf menhaden caught during the summer of 2011. Many Matrix Solid Phase Dispersion (MSPD) methods require specific cartridges and other clean-up materials in order to achieve proper extraction. For this study, the tissues were lyophilized prior to applying the adapted MSPD method allowing for a much more complete homogenization with the C18 silica. The tissue was spiked with phenanthrene d10 as a surrogate as a measure of PAH recovery prior to the lyophilisation process to determine if any target compounds were lost and prior to sonication as per the finalized adaptation procedure to determine method efficiency. This technique used C18 silica in a 1: 1 ratio as the primary homogenizing material for the menhaden tissue matrix and was eluted with dichloromethane (DCM) until visibly clear. The overall study mean recovery was 88% ±5% with method detection limits between 0.4ng/g and 4.4ng/g tissue dry weight. This adapted protocol has been used exclusively on the analysis of high lipid content fish stocks affected by dispersed and weathered oil from the BP Horizon incident. [ABSTRACT FROM AUTHOR]

Abstract: Harmful algal blooms are an increasing problem for coastal waters world-wide. The presence of the toxigenic diatom genus Pseudo-nitzschia is of concern in the Gulf of Mexico, due to the potential for several species in this genus to produce the neurotoxin domoic acid (DA). Louisiana coastal waters are of particular interest due to the presence of both toxin-producing species of Pseudo-nitzschia and abundant potential vectors. While trophic transfer of DA to consumers has repeatedly occurred along the California coast, little is known about trophic transfer of recently detected DA in the Gulf of Mexico. In this study, the presence of DA was investigated in filter-feeding gulf menhaden (Brevoortia patronus) and in seawater where high abundances of these fish reside. Pseudo-nitzschia presence and enumeration was determined using light microscopy, species identification in seawater and gulf menhaden gut contents was conducted with transmission electron microscopy (TEM), and DA quantification in corresponding seawater and tissue samples was determined by competitive enzyme-linked immunosorbent assay (cELISA). Examination of the phytoplankton revealed the presence of four species of Pseudo-nitzschia: P. calliantha for the first time, P. pseudodelicatissima, P. pungens, and P. americana, with P. calliantha as the dominant Pseudo-nitzschia species. Low levels of DA were detected in both seawater and fish samples, with a significant correlation between the two (n =22, p =0.043). Thus, for the first time in the Gulf of Mexico, a potential vector of DA has been identified, revealing the possibility of DA contamination in coastal Louisiana food webs. [ABSTRACT FROM AUTHOR]

Clupeiform fish species, including the Gulf menhaden (Brevoortia patronus) that belong to the subfamily Alosinae, can detect ultrasound. Clupeiform fishes are unique in that they have specialized gas-filled bullae in the head associated with the ear via the bulla membrane and with the lateral line via the lateral recess membrane. It has been hypothesized that the utricle of the inner ear is responsible for ultrasound detection through a specialized connection to the gas-filled bullae complex. Here, we show that the lateral line and its connection to the gas-filled bullae complex via the lateral recess are involved in ultrasound detection in Gulf menhaden. Removal of a small portion of the lateral line overlying the lateral recess membrane eliminates the ability of Gulf menhaden to detect ultrasound. We further show that the gas-filled bullae vibrates in response to ultrasound, that the gas-filled bullae are necessary for detecting ultrasound, and that the bullae connections to the lateral line via the lateral recess membrane play an important role in ultrasound detection. These results add a new dimension to the role of the lateral line and bullae as part of the ultrasonic detection system in Gulf menhaden. [ABSTRACT FROM AUTHOR]

Boswell, K. M., Roth, B. M., and Cowan, Jr J. H. 2009. Simulating the effects of side-aspect fish orientation on acoustic biomass estimates. – ICES Journal of Marine Science, 66: 1398–1403.Simulation methods were used to investigate the effect of side-aspect fish orientation on estimates of fish biomass derived from acoustic data. Three population-level length distributions (n = 1000 individuals) were simulated (identical, uniform, and age class) and applied to a target strength (TS) function of fish length previously derived for Gulf menhaden (Brevoortia patronus). Systematic manipulation of the TS–length coefficients strongly affected the biomass estimates. Based on simulations, biomass estimates decreased markedly from the true side-aspect to head- or tail-on orientation, with estimates of population biomass decreasing by 80% when orientation deviated by as little as 30° from true side-aspect. Simulated data indicate that biomass estimates generated from surveys may be grossly inaccurate if fish orientation is not taken into account. [ABSTRACT FROM PUBLISHER]

Boswell, K. M., and Wilson, C. A. 2008. Side-aspect target strength measurements of bay anchovy (Anchoa mitchilli) and Gulf menhaden (Brevoortia patronus) derived from ex situ experiments. – ICES Journal of Marine Science, 65: 1012–1020.Acoustic target strengths (TSs) of bay anchovy [Anchoa mitchilli, 4.7–6.1 cm TL (total length)] and Gulf menhaden (Brevoortia patronus, 5.1–7.7 cm TL) were measured at 420 kHz during side-aspect, ex situ experiments. TS–TL relationships were derived at aspect for tethered individuals, and TS distributions were compared with those of free-swimming fish. Linear models relating TS and TL were fitted to data at two levels of pulse duration (0.1 and 0.4 ms) for both side aspect and all horizontal aspects of each species, and for pooled data from both species. At a pulse duration of 0.4 ms, the side-aspect TS–TL relationships were anchovy: TSlateral = 19.5 log10 TLcm − 62.4; menhaden: TSlateral = 26.1 log10 Lcm − 65.6; pooled: TSlateral = 32 log10 TLcm − 70.9. For all horizontal-aspect orientations (0–180° in the horizontal) the best-fit TS–TL relationships were anchovy: TSall = 20 log10 TLcm− 65.4; menhaden: TSall = 20 log10 TLcm − 64.8; pooled: TSall = 20 log10 TLcm− 65. However, the “fit” for all angles was consistently low. Predicted TS comparisons with side-aspect models presented by earlier authors suggested biases in the estimated TL. Additionally, relationships between TS and wet weight (W) were derived for each species. Variation in TS by pulse-duration level suggests the potential for the use of this factor as a time-dependent variable by which to separate echoes from bay anchovy and Gulf menhaden. [ABSTRACT FROM PUBLISHER]

The designation of Texas as a "hotspot" for fish mortalities relative to the other 22 coastal US states is of serious concern for scientists, resource managers, and the public alike. We investigated the major sources and causes of fish kills in coastal Texas from 1951 to 2006. During this 55-year period, more than 383 million fish were killed, 72% of which were Gulf menhaden (Brevoortia spp.). We examined the relationships between climate and the physical features of Texas bays and estuaries as well as the consequences of high-density industrialization and urbanization along several coastal centers on fish kills, including the impact of eutrophication, algal blooms (toxic and nontoxic), and hypoxia. Galveston and Matagorda Bays had the highest number of fish kill events and total number of fish killed. The largest number of fish kill events and the highest number of fish killed occurred during the warmest months, particularly in August. The leading cause of fish kills was found to be low dissolved oxygen concentrations caused by both physical and biological factors. From 1958 to 1997, about two thirds of the mortalities from low oxygen concentrations were caused by human activities. With the population predicted to double in Texas by 2050, mostly along the coastal areas, natural resources will require additional protection. Further increases in nutrient loading are expected in areas unable to keep up with construction of sewage treatment facilities. Defining the sources and causes of fish kill events in Texas will allow better management and conservation efforts. [ABSTRACT FROM AUTHOR]

Hybridization between the North American menhadens Brevoortia smithi, Brevoortia tyrannus and Brevoortia patronus has been reported by numerous authors, based primarily on the morphological intermediacy of hybrids relative to each parental type. In this study, genetic characterization of individuals in areas previously designated as hybrid zones validates the presence of F1 hybrids. Evidence from microsatellite genotypes indicates that B. patronus and B. smithi are parental species of hybrids on both sides of the Florida peninsula, and mitochondrial DNA (mtDNA) haplotypes suggest a maternal contribution by B. smithi in each case. Hybrids between B. tyrannus and B. smithi were not identified in this study. The presence of B. patronus on the Atlantic coast of Florida, coupled with admixture between this species and B. tyrannus, has likely influenced the mixed lineage assortment of mtDNA haplotypes demonstrated in this study and in previous studies. [ABSTRACT FROM AUTHOR]

Gulf menhaden Brevoortia patronus, the main target of a commercial fishing industry in the Gulf of Mexico, and finescale menhaden Brevoortia gunteri, a non-targeted congeneric, have historically been difficult to differentiate. In this study, meristic counts resulted in two of three characteristics that clearly distinguished species, and genetic differences included 1) near fixation for different alleles between species at two of five loci and 2) significantly large divergence ( FST) values between species at four loci. Implications for the correct identification of these species and their putative hybrids are discussed. [ABSTRACT FROM AUTHOR]

Abstract: Gulf menhaden, Brevoortia patronus, plays a key ecological role in the northern Gulf of Mexico and supports the second largest commercial fishery by weight in the United States. Here we describe that fishery and propose biological reference points (BRPs) for its management. The BRPs represent targets and limits of both fishing mortality rate (F) and population fecundity (Ψ), where target is defined as the management goal, and limit, a value to be avoided (F < F Limit and Ψ > Ψ Limit). We assess stock status relative to the BRPs by fitting a statistical catch-age model to fishery-dependent and fishery-independent data spanning 1964–2004. Results indicate that in the terminal year neither limit reference point is exceeded (F 2004/F Limit =0.75 and Ψ 2004/Ψ Limit =1.86). Of possible concern, however, is a recent increase in fishing mortality and decrease in population fecundity. With these trends, terminal values exceed their targets (F 2004/F Target =1.16 and Ψ 2004/Ψ Target =0.93), although by little relative to uncertainty in the estimates. Sensitivity analyses show these results are robust to model assumptions. [Copyright &y& Elsevier]

Continuous records of annual landings and fishing effort exist in the Atlantic purse-seine fishery for Atlantic menhaden Brevoortia tyrannus since 1940 and the Gulf of Mexico fishery for Gulf menhaden B. patronus since 1946. Currently, year-ahead forecasts of landings from these species-specific fisheries separated by the Florida peninsula are provided to the industry by means of multiple linear-regression models that relate landings and effort over the data series. Here, we compare three methods for this purpose--multiple regression, time series, and artificial neural networks--to determine whether forecast accuracy can be increased. Best-fit models were developed with each method for each fishery, and then 10-year retrospective analyses of 1-year-ahead catch forecasts were compared among the three methods. In general, multiple-regression and artificial neural network models were similar in their fit to the data series and both were better than time series models, judging from the Akaike information criterion, the correlation between observed and predicted catches, the mean prediction error, and the root mean square error of prediction. A 10-year retrospective analysis (1993-2002) of 1-year-ahead catch forecasts indicates that the three methods provided similar within-stock mean absolute forecast errors (19-21% in the Atlantic and 15-20% in the Gulf), with generally better forecasts for the Gulf fishery. Overall, multiple-regression and artificial neural network models provide lower average catch forecast errors and better tics to the fishery data, whereas similar forecast errors are provided by a univariate time series model (autoregressive integrated moving average model) in the Atlantic and a multivariate time series model (state space model) in the Gulf. [ABSTRACT FROM AUTHOR]

Fishery observers collected data from 307 tows during 96 trips aboard skimmer trawl vessels in Louisiana's coastal waters from September 2004 through June 2005 to estimate catch rates of target and nontarget species, including sea turtles (Cheloniidae and Dermochelyidae), by area and season during commercial shrimping operations. About 16,965.7 kg of total catch were recorded during 517.0 hours of fishing operations. Based on weight extrapolations from species composition samples, penaeid shrimp (Penaeidae) dominated the catch at 66%, followed by finfish at 19%, nonpenaeid shrimp crustaceans at 7%, discarded penaeid shrimp at 6%, and debris at 3%. Noncrustacean invertebrates comprised less than 1%. Catch rates in kilograms per hour by category was 21.6 for penaeid shrimp, 6.2 for finfish, 2.2 for nonpenaeid crustaceans, 1.8 for discarded penaeid shrimp, and 0.9 for debris. White shrimp, Litopenaeus setiferus, other penaeid shrimp, and Gulf menhaden, Brevoortia patronus, were the top three dominant species by weight. Seasonally, a higher catch rate was observed from May through August 2005 for penaeid shrimp as compared with the September through December 2004 period. Conversely, the September through December 2004 period experienced a higher catch rate for finfish than during May through August 2005. No sea turtle interactions were documented. [ABSTRACT FROM AUTHOR]

Larval and juvenile development of finescale menhaden (Brevoortia gunteri) is described for the first time by using wild-caught individuals from Nueces Bay, Texas, and is compared with larval and juvenile development of co-occurring gulf menhaden (B. patronus). Meristics, morphometrics, and pigmentation patterns were examined as development proceeded. An illustrated series of finescale menhaden is presented to show changes that occurred during development. For finescale menhaden, transformation to the juvenile stage was completed by 17-19 mm standard length (SL). By contrast, transformation to the juvenile stage for gulf menhaden was not complete until 23-25 mm SL. Characteristics useful for separating larval and juvenile finescale menhaden from gulf menhaden included 1) the presence or absence of pigment at the base of the insertion of the pelvic fins; 2) the standard length at which medial predorsal pigment occurs; 3) differences in the number of dorsal fin ray elements; and, 4) the number of vertebrae. [ABSTRACT FROM AUTHOR]