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Emerging diseases of wildlife are an existential threat to biodiversity, and human-mediated movements of live animals are a primary vector of their spread. Wildlife disease risk analyses offer an appealing alternative to precautionary approaches because they allow for explicit quantification of uncertainties and consideration of tradeoffs. Such considerations become particularly important in high-frequency invasion pathways with hundreds of thousands of individual vectors, where even low pathogen prevalence can lead to substantial risk. The purpose of this study was to examine the landscape-level dynamics of human behavior-mediated pathogen introduction risk in the context of a high-frequency invasion pathway. One such pathway is the use and release of live fish used as bait by recreational anglers. We used a stochastic risk assessment model parameterized by angler survey data from Minnesota, USA, to simulate one year of fishing in Minnesota and estimate the total number of risky trips for each of three pathogens: viral hemorrhagic septicemia virus, the microsporidian parasite Ovipleistophora ovariae , and the Asian fish tapeworm Schizocotyle acheilognathi. We assessed the number of introductions under four scenarios: current/baseline conditions, outbreak conditions (increased pathogen prevalence), source-focused control measures (decreased pathogen prevalence), and angler-focused control measures (decreased rates of release). We found that hundreds of thousands of introduction events can occur per year, even for regulated pathogens at low pathogen prevalence. Reducing the rate of illegal baitfish release had significant impact on risky trips in scenarios where a high number of anglers were involved, but was less impactful in circumstances with limited outbreaks and fewer affected anglers. In contrast, reducing pathogen prevalence in the source populations of baitfish had relatively little impact. In order to make meaningful changes in pathogen introduction risk, managers should focus efforts on containing local outbreaks and reducing illegal baitfish release to reduce pathogen introduction risk. Our study also demonstrates the risk associated with high-frequency invasion pathways and the importance of incorporating human behaviors into wildlife disease models and risk assessments. [ABSTRACT FROM AUTHOR]

Pollution from recreational fishing gear can have a significant effect on aquatic species and the environment. For these reasons, the development of more environmentally friendly fishing gear is desired to reduce the amount of marine litter caused by recreational angling. Several attempts have been made to develop biodegradable fishing baits; however, the strength, wear resistance, and water interaction properties of these baits are suboptimal. In this study, various compositions of biodegradable lures were manufactured to investigate the influence of the individual components on the important bait properties including strength, heat resistance, swelling, viscosity, and porosity. By investigating the important lure properties, the results can be compared to commercially available soft plastic lures. The baits manufactured with a low percentage of water and a high percentage of xanthan gum showed increased strength and the lowest porosity; however, these baits increased in size and weight the most during the swelling test. The lures fabricated using a high percentage of water and a low percentage of beef gelatin showed the least amount of swelling, which is desired. Lastly, the lures manufactured with a high percentage of water and a low percentage of vegetable glycerin allowed for the best heat resistance properties. The results discussed in this paper will aid in completing further formula optimizations to improve the properties of the biodegradable lures. Advances in the development of more environmentally friendly fishing tackle is essential to reduce the impact that lost and discarded fishing gear can have on the environment and wildlife. By investigating the properties of biodegradable fishing lures, progression of more sustainable alternatives can be explored to protect from the toxic chemicals and plastics that soft plastic lures contain. [ABSTRACT FROM AUTHOR]

Aquaculture of baitfish has the potential to produce and supply desired species and sizes to meet year-round market demand. The Seminole KillifishFundulus seminolisis native to Florida and has recently emerged as a candidate for marine baitfish aquaculture because of its ability to survive acclimation to seawater, fast growth, and resilient larvae. Experiments were conducted to identify which spawning substrate materials and orientations were preferred by Seminole Killifish and to evaluate effects of broodfish stocking density on reproductive output. Results indicated that Seminole Killifish required a suitable substrate to be present for successful spawning and egg deposition. Broodstock spawned nearly all eggs onto fiber spawning mats when offered both mat and sand substrates. There was no significant difference in the number of eggs recorded among spawning mats regardless of orientation. Seminole Killifish held in outdoor tanks at a 2:1 (female : male) sex ratio had similar total egg production per tank per week irrespective of stocking density (10, 20, or 30 fish/m3). Consequently, the mean number of eggs produced per female was significantly different among the treatment densities, and an inverse relationship was noted between egg production and stocking density. Causes of observed fecundity differences among treatment densities are discussed along with other observations relevant to production. Received January 18, 2017; accepted May 10, 2017Published online May 22, 2017 [ABSTRACT FROM PUBLISHER]

Baitfish producers have expressed interest in adopting the split-pond production system. However, confining fish to 20% of the pond area in split-pond systems effectively quintuples fish density within the culture unit as compared with densities in open ponds. Winter conditions are known to be relatively more stressful on smaller fish, and high densities within split-pond culture units could increase losses. A 139-d study was conducted during the winter to compare the production of golden shiners, Notemigonus crysoleucas, in traditional earthen ponds and split ponds at two densities. Golden shiners were stocked at 646 kg/ha or 1292 kg/ha (ca. 370,500 or 741,000 fish/ha, respectively) into 12, 0.04-ha, netted earthen ponds (six split ponds and six traditional). Feeding rate, nightly aeration hours, and daily circulation hours were reduced when water temperature decreased. At harvest, net yields were significantly lower in the split ponds as compared with traditional ponds at each density (53 and 113 kg/ha less in the low- and high-density split-pond treatments, respectively). Estimated survival was high (>87%) and did not differ among treatments. Results showed that, although net yield was reduced, small baitfish could be successfully overwintered in split-pond culture units in preparation for the spring crappie market. [ABSTRACT FROM AUTHOR]

Spawning performance of pinfish Lagodon rhomboides without use of hormonal aids was monitored over an extended season. Nearly three million eggs were obtained from 75 spawns collected over a 90-day consecutive period from a single population of four brood fish (1M:1F). A mean ± s.d. batch fecundity of 30·27 ± 22·64 eggs g−1 female was estimated with 98·0 ± 0·06% of the batch composed of floating eggs which were 1·04 ± 0·04 mm in diameter and 85·71 ± 27·59% fertile. Floating eggs successfully hatched 54·65 ± 29·13% of the time which yielded larvae that were 2·59 ± 0·24 mm in length. Fatty acids within floating eggs were largely represented by polyunsaturated fatty acids (45·30 ± 2·14% of total fatty acids) of which linoleic acid [(c18:2 n-6cis) 3·49 ± 1·69% trifluoroacetic acid (TFA)] and docosahexaenoic acid (DHA) [(c22:6 n-3) 28·47 ± 1·48% TFA] represented the majority of fatty acids for n-6 and n-3 polyunsaturated fatty acids, respectively. The strongest correlations between fatty acids and hatching success and larval survival to first feeding were observed for the DHA:EPA (eicosapentaenoic acid; c20:5 n-3) ratio and total n-6 polyunsaturated fatty-acids levels, respectively. These data demonstrate potential for producers to rely on natural spawns for extensive egg production and provide a baseline for future development of natural spawning protocols of captive L. rhomboides. [ABSTRACT FROM AUTHOR]

Rynchops niger (Black Skimmer) is a colonial seabird that forages on small planktivorous fish that are caught while gliding just above the surface. Previous studies have found that baitfish abundance can affect skimmer productivity, so the purpose of this research was to determine the species and size of fish fed to chicks in Southwest Florida. During the 2015 and 2016 nesting seasons, we posted requests for photographs of Black Skimmer adults feeding chicks to several Facebook sites where photographers were posting images taken in Southwest Florida. We invited volunteers who were knowledgeable about fish to identify prey species. We received 256 photographs of which 211 could be included in our study. Black Skimmers fed chicks 22 different species of fish, including 9 that had not been previously recorded. The fish species did not differ by year, age of chick, or location; however, smaller chicks were fed significantly more small fish. Our research demonstrated that citizen science conducted through using photographs and social media is an accurate and efficient method of obtaining data about seabird diets. [ABSTRACT FROM AUTHOR]

Pinfish ( Lagodon rhomboides Linnaeus) and pigfish ( Orthopristis chrysoptera L.) are relatively new, cultured species commonly used as marine baitfish in the south-eastern United States and currently have no defined protocols for egg incubation. Thus, experiments were conducted to determine efficient egg stocking densities during static and flow-through incubation that yielded higher quality larvae. Eggs of each species were incubated statically at 250, 500, 1000 and 2000 eggs L−1, and after incubation, egg hatching success, larval survival to first feeding, larval morphometrics and water quality were assessed. Stocking densities above 250 eggs L−1 led to significant reductions in pinfish hatching success and water quality degradation, evident from decreased dissolved oxygen and pH levels and increased nitrogenous wastes. Increased stocking densities for pigfish also resulted in significant water quality degradation, although hatching success was unaffected up to a density of 1000 eggs L−1. A high flow-through water exchange rate of 2000% daily resulted in significant reductions in nitrogenous wastes and greater stability in dissolved oxygen and pH levels during incubation when compared to static treatments of the same egg density. Additionally, the high exchange rate of 2000% was critical in maintaining high hatching success and larval survival to first feeding at stocking densities of 1000 eggs L−1 for pinfish and up to 4000 eggs L−1 for pigfish. No clear patterns in larval morphometrics were observed among stocking densities. Static incubation densities of 250 and 1000 eggs L−1 are recommended for pinfish and pigfish, respectively. [ABSTRACT FROM AUTHOR]

The US regulatory environment has been characterized as complex due to the greater than 1300 laws promulgated at local, state, and federal levels. Recent declines in the growth rate of US aquaculture have been attributed, in part, to a complex, overlapping, and inefficient regulatory framework. This study is the first to examine this question by quantifying the farm-level regulatory burden and its economic effects in an aquaculture industry sector. A survey was conducted of baitfish and sportfish producers in the 13 major production states in the USA to identify the direct and indirect costs of regulation on producers. Survey responses captured 74% of the national volume of baitfish and sportfish production. The data revealed that only 1% of total regulatory costs are direct costs of regulation, such as license and permit fees, while 99% of the costs are due to manpower used for compliance, farm changes to remain in compliance, and sales lost without replacement. Costs due to regulations varied across states and farm sizes. Across all respondents, average total regulatory costs were found to be $148,554/farm, or $7383/ha. The farm-level cost to the US baitfish and sportfish industry was estimated to be in excess of $12 million. On 38% of the farms, the cost of regulations exceeded the value of profits on baitfish and sportfish farms. Our findings confirm previous reports of the complexity of the regulatory environment. Results show that the total regulatory burden has increased farm-level costs and restricted access to markets, thereby reducing profitability and contributing to reduced growth of the US baitfish and sportfish industry. [ABSTRACT FROM AUTHOR]

Pigfish (Orthopristis chrysoptera Linnaeus) are a commonly used baitfish in the southeastern United States. Aquaculture methods for broodfish spawning and juvenile grow-out have been developed but there is still a paucity of information regarding larval culture methods. Five, short duration (10 days) experiments were conducted to determine effective strategies to yield high larval survival and growth during early development. Experiment one examined the rotifer enrichments Ori-Green, DHA Protein Selco, and AlgaMac 3050 as well as a non-enriched control along with corresponding fatty acid levels in the enriched rotifers and pigfish larvae. Experiment two evaluated three, once daily feeding frequencies of either 5, 10 or 20 rotifers mL-1. Experiment three compared feeding 20 rotifers mL-1 once daily to feeding 5 rotifers mL-1 twice daily. Experiment four examined four different larval stocking densities: 50, 75, 100, or 125 larvae L-1. Experiment five examined green water strategies using either live Tahitian strain Isochrysis galbana (Parke) or Nannochloropsis oculata (Hibberd) paste at either 250 000 or 500 000 cells mL-1 as well as a clear water control. Results indicated rotifer enrichment with DHA Protein Selco and green water application using live T-ISO at 500 000 cells mL-1 had the highest survival of pigfish during early stages of larval culture. A once daily rotifer feeding regime of 20 rotifers mL-1 and stocking density of 50 larvae L-1 also improved survival. These results provide producers with methods to improve efficiency for pigfish larval culture and provide researchers with new foundational data, such as potential fatty acid requirements. [ABSTRACT FROM AUTHOR]

Together with CYCT1;3 (Cyclin T), CDKC;2 phosphorylates Ser5 of the C-terminal domain (CTD) of RNA polymerase II (Pol II) and alters the transcriptional levels of various genes, including clock-associated genes. Circadian clocks in eukaryotes consist of a complex feedback mechanism in which multiple clock genes regulate each other during transcription, translation and post-translational modifications. [Extracted from the article]

Tunas caught by the baitboat fleet are one of the most sustainable products of the high seas. We analyzed catches of the baitboat fleet operating off northwestern Mexico from 1978 to 2013. We assessed the relationship between the standardized tuna catch and the Multivariate El Niño Index (MEI), the Pacific Decadal Oscillation (PDO), and landings of the two main species (Pacific sardine, Sardinops sagax , and northern anchovy, Engraulix mordax) used as baitfish in the Northeastern Pacific Ocean tuna fishery. Results showed a strong correlation between yellowfin tuna (Thunnus albacares) catches and sardine landings, and an inverse correlation between yellowfin tuna catches and both MEI and PDO. Yellowfin tunas are more abundant during colder-than-normal conditions. We hypothesized that, when the sardine population is more vulnerable to the small-pelagic fishery in the Gulf of California, environmentally ideal conditions, as well as baitfish (sardine) availability, resulted in high yellowfin tuna landings. The opposite behavior was observed for the standardized catch of skipjack tuna (Katsuwonus pelamis): a strong correlation with anchovy landings and a positive correlation with both MEI and PDO suggested that there is an alternation between tuna and small pelagic species. [ABSTRACT FROM AUTHOR]

During a survey of apparently healthy baitfish from the state of Minnesota, a novel piscine-myocarditis-like virus (PMCLV) was detected in golden shiners ( Notemigonus crysoleucas). The nearly complete genome sequence is 5819 nt long, including a partial 5' untranslated region (UTR) of 100 nt. The sequence is divided into three ORFs: the complete ORF1 and ORF2, encoding proteins of 818 and 831 amino acids, respectively, and a partial ORF3 encoding 248 amino acids of the corresponding protein. This novel virus sequence was most closely related to piscine myocarditis virus (PMCV), with a 49.0 % and 58.2 % amino acid identity in the ORF1 (YP005481249)- and ORF2 (YP004581250)-encoded proteins, respectively. Six of 56 retail outlets (e.g., bait shops) were positive during the 2014-2015 survey, indicating a 10.7 % prevalence of the novel virus in this population of golden shiners. Currently, there is no disease that is known to be associated with this virus. [ABSTRACT FROM AUTHOR]

A new host record for Pseudocapillaria (Pseudocapillaria) tomentosa (Dujardin, 1843) Moravec, 1987 from the intestine of red shiner, Cyprinella lutrensis, imported from a commercial facility in Missouri to a research facility in Wisconsin is described. Prevalence of infection was 85%. Intensity of infection was 1-26 worms per host. Supplementary information involving sequence data (18S ribosomal RNA gene) and new details of the male spicule are provided. The issue of parasite dispersal through the baitfish trade is briefly discussed. [ABSTRACT FROM AUTHOR]

The article traces the historic flight of Franklin's Gull in 2015. Details are provided on the autumn migration of Franklin's Gull in Connecticut associated with cold temperatures and northwest winds, concentration of small baitfish throughout Long Island Sound, and low pressure system through the central plains and upper Midwest. An estimate of the number of Franklin's Gulls that arrived in Connecticut during this period is given.

The golden shiner, Notemigonus crysoleucas, is a major bait and forage fish species in the USA. Farmers produce millions of golden shiners annually that are distributed live, many across state boundaries. Native over much of the eastern and central USA, this species is often present but rarely abundant in natural systems, as fish density is apparently controlled by predation rather than by food resources. Aquaculture of the golden shiner is a century-old practice and culture methods have evolved over time, resulting in today's farm-raised, certified specific pathogen- and aquatic nuisance species-free baitfish. Federal and state agencies and universities have a long history of developing culture methods and promoting baitfish culture to replace the indiscriminate and wasteful harvest of fish from natural waters. Despite advances in culture methods and the advantages of a farm-raised species produced under controlled and biosecure conditions, golden shiner farming is only marginally profitable and remaining farmers survive on farm equity and increased market share from others exiting the business. Ironically, increasing regulations and restrictions leading to a reduction in the supply of farm-raised baitfish could drive anglers back to harvesting bait from natural waters, the very concern that initiated government support for baitfish culture a century ago. [ABSTRACT FROM AUTHOR]

This paper reports the results of using different hook style and bait type combinations on the catches of targeted, bycatch and discarded fishes in the Portuguese commercial longline fishery targeting swordfish ( Xiphias gladius) in the South Atlantic Ocean., In total, 310 longline experimental sets (446 400 hooks) were deployed between October 2008 and February 2012. Three different hook styles were tested; the traditional J-hook (9/0) 10o offset was compared with two 17/0 circle hooks (a non-offset and a 10o offset), and squid ( Illex spp.) bait was compared with mackerel ( Scomber spp.)., Catch per unit effort (CPUE) was calculated for each fish species per fishing set and compared between the different hook style and bait type combinations. Results indicated that the effects of hook style and bait on the CPUEs were species-specific. For example, swordfish (target species, Xiphias gladius) CPUEs were higher with J-hooks baited with squid, while for the blue shark (most important bycatch species, Prionace glauca) the highest CPUEs were obtained with circle hooks baited with mackerel. For tuna ( Thunnus spp.) and marlin (blue, Makaira nigricans and white, Kajikia albida) only the bait effect was significant, with higher catches with squid., For the discarded species, the proportions of alive vs dead specimens at the time of fishing gear retrieval were also species-specific., The total retained catch value per unit of effort (VPUE) did not changed between the different hook and bait combinations, but these VPUEs are highly dependent on market fluctuations., Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Managing risky human behaviour involving invasive species, such as unauthorized stocking or the release of pets to the wild, is difficult because the rationale for risk taking is often unknown. To identify factors that increase the likelihood of risky behaviour, we conducted social surveys and analyzed perceptions about invasive species, natural resource management, social norms, and outreach initiatives for live bait anglers in Ontario, Canada and Michigan, USA. We used classification trees to predict risky behaviour (release of fishes; Ontario, P = 0.197, Michigan, P = 0.275) based on patterns of variation in social perceptions. Irrespective of release, respondents generally agreed with (and exhibited strong willingness to pay for) prevention management, despite only moderate consensus that natural resource use had been impacted by invasive species. The most parsimonious model to predict release was based on the convenience of releasing fishes and the (mis)perception that released fishes provide an ecological benefit to natural resources, which held for 70.5 % of risk takers (classification rate = 80.6 %, true negative rate = 84.6 %, AUC = 0.81). Therefore, perceptions other than those directly involving invasive species strongly increase the likelihood that an individual will release fishes to the wild. For a subset (29.5 %) of risk takers, release behaviour was unpredictable and lacked obvious rationale; therefore, additional invasive species management efforts remain justified to offset individual actions that may never be understood with certainty and for which targeted social outreach strategies are likely ineffective. [ABSTRACT FROM AUTHOR]

Pigfish ( Orthopristis chrysoptera ) have been identified as a good candidate for marine baitfish aquaculture. Initial research on the species has focused on captive spawning and larval rearing, but optimizing juvenile grow-out is also essential for economical production. We conducted an experiment to determine the optimal ration (R opt ) for maximizing growth rate while minimizing size variability and overfeeding. We measured total length (TL), wet weight (WW), specific growth rate (SGR), gross feed conversion efficiency (GFCE), and survival of juvenile pigfish (initial size: 2.6 ± 0.4 cm TL) using six ration levels (4, 8, 12, 16, 20, or 24% WW d − 1 ) for four weeks at 24.7 ± 0.2 °C. Final size (TL and WW) increased with increasing ration at lower rations, reaching a plateau at intermediate levels (8–16% WW d − 1 ). Survival increased with ration from 74% at the lowest ration to a plateau of 96.0% at rations > 10.7% WW d − 1 . GFCE decreased with increasing ration from 149% to 47%. To identify R opt and its change with fish size, we modeled SGR as a function of WW, ration, and their interaction and found that R opt = 11.19 · WW − 0.26 (R 2 = 0.70, P < 0.05). This equation provides a guide for producing pigfish quickly and efficiently and, with further research on culture requirements, can be used to establish an efficient pigfish grow-out protocol. [ABSTRACT FROM AUTHOR]

The use of live baitfish is a cultural norm in many jurisdictions across North America. Because baitfish are often harvested from mixed stocks in the wild, the potential for bycatch exists, leading to the inadvertent relocation of nontarget species via distribution networks and anglers; therefore, like many fisheries, core issues revolve around selective fishing. We assess selectivity of bait fisheries in Ontario, focusing on the prevalence of bycatch within the commercial supply chain and the propensity for nontarget species introductions by anglers. Selection for target stocks was strong; however, species assemblages in retail tanks and angler purchases included game, imperiled, invasive, and other nontarget species. The combination of bycatch, a large volume of angling trips, and risky angler behavior results in high probabilities of introducing the suite of nontarget species contained incidentally. Pathway approaches to management provide opportunities to increase selectivity, manage the risk of species introductions, and sustain the integrity of bait operations throughout North America. RESUMEN: el uso de carnada viva es una norma cultural en varias jurisdicciones de Norte América. Debido a que los peces que se utilizan como carnada a veces son capturados junto con una mezcla de stocks silvestres, existe el potencial de que se vuelvan fauna de acompañamiento, lo que tiene como consecuencia que especies no objetivo sean reubicadas de forma inadvertida a través pescadores y de redes de distribución; por esta razón, como sucede en muchas pesquerías, el problema medular gira en torno a la pesca selectiva. En este trabajo se evalúa la selectividad de las pesquerías de carnada en Ontario, Canadá, haciendo enfasis en la prevalencia de la fauna de acompañamiento en la cadena productiva y en la propensión que existe por parte de los pescadores a reubicar especies no objetivo. La selectividad que existe para los stocks objetivo es intensa, sin embargo las asociaciones de peces que comercializan los pescadores incluyen especies de pesca deportiva, especies en peligro, especies invasivas y otras especies no objetivo. La combinación de fauna de acompañamiento, una enorme cantidad de viajes de pesca y un comportamiento riesgoso por parte de los pescadores, da como resultado una alta probabilidad de introducir una amplia gama de especies no objetivo que son contenidas incidentalmente. El manejo utilizando corredores, podria incrementar la selectividad, controlar la introducción de especies y mantener la integridad de las operaciones pesqueras con carnada a lo largo de Norte América. [ABSTRACT FROM AUTHOR]

During both regulatory and routine surveillance sampling of baitfish from the states of Illinois, Minnesota, Montana, and Wisconsin, USA, isolates (n = 20) of a previously unknown picornavirus were obtained from kidney/spleen or entire viscera of fathead minnows (Pimephales promelas) and brassy minnows (Hybognathus hankinsoni). Following the appearance of a diffuse cytopathic effect, examination of cell culture supernatant by negative contrast electron microscopy revealed the presence of small, round virus particles (∼30–32 nm), with picornavirus-like morphology. Amplification and sequence analysis of viral RNA identified the agent as a novel member of the Picornaviridae family, tentatively named fathead minnow picornavirus (FHMPV). The full FHMPV genome consisted of 7834 nucleotides. Phylogenetic analysis based on 491 amino acid residues of the 3D gene showed 98.6% to 100% identity among the 20 isolates of FHMPV compared in this study while only 49.5% identity with its nearest neighbor, the bluegill picornavirus (BGPV) isolated from bluegill (Lepomis macrochirus). Based on complete polyprotein analysis, the FHMPV shared 58% (P1), 33% (P2) and 43% (P3) amino acid identities with BGPV and shared less than 40% amino acid identity with all other picornaviruses. Hence, we propose the creation of a new genus (Piscevirus) within the Picornaviridae family. The impact of FHMPV on the health of fish populations is unknown at present. [ABSTRACT FROM AUTHOR]

Threadfin shad (Dorosoma petenense) is a schooling pelagic forage fish native to watersheds of the Gulf Coast of North America. Around 1962 it invaded the Sacramento-San Joaquin Delta from upstream reservoirs, where it was stocked to support sport fisheries. It quickly became, and continues to be, one of the most abundant fishes collected by ongoing monitoring programs in the delta. A substantial portion of the delta provides suitable abiotic habitat and so the species is widely distributed. However, in routine sampling it is most commonly collected and most abundant in the southeastern delta, where suitable abiotic habitat (relatively deep, clear water with low flow) coincides with high prey abundance. Apparent growth rate appears to be relatively fast with summer-spawned age-0 fish attaining fork lengths of 70 to 90 mm by the onset of winter. During fall months (September through December) apparent growth rate of age-0 fish has exhibited no long-term trend but has been negatively related to abundance, suggesting that density-dependent factors may be important to the population. Although abundance has fluctuated since its introduction almost five decades ago, it has recently dropped to persistent near-record lows since 2002, which has been coincident with similar declines for other pelagic species in the delta. The recent decline is apparent in two long-term monitoring programs, fish salvaged from the diversions of the state and federal water projects, and commercial fishing harvest. It appears that the decline is, at least in part, a function of fewer and smaller schools of threadfin shad encountered relative to the past. There was little evidence from the data examined for consistent stock-recruit or stage-recruit effects on the population. It is likely that a combination of abiotic and biotic factors regionally-focused where threadfin shad are most abundant, which may sometimes be episodic in nature, have a large effect on abundance. Focused studies and sampling of threadfin shad are lacking but are necessary in order to better understand population dynamics in the delta.