Lack of genetic differentiation in yellowfin tuna has conservation implications in the Eastern Pacific Ocean.

Yellowfin tuna, Thunnus albacares, is an important global fishery and of particular importance in the Eastern Pacific Ocean (EPO). According to the 2019 Inter-American Tropical Tuna Commission (IATTC) assessment, yellowfin tuna within the EPO is a single stock, and is being managed as one stock. However, previous studies indicate site fidelity, or limited home ranges, of yellowfin tuna which suggests the potential for multiple yellowfin tuna stocks within the EPO, which was supported by a population genetic study using microsatellites. If numerous stocks are present, management at the wrong spatial scales could cause the loss of minor yellowfin tuna populations in the EPO. In this study we used double digestion RADseq to assess the genetic structure of yellowfin tuna in the EPO. A total of 164 yellowfin tuna from Cabo San Lucas, México, and the Galápagos Islands and Santa Elena, Ecuador, were analysed using 18,011 single nucleotide polymorphisms. Limited genetic differentiation (FST = 0.00058-0.00328) observed among the sampling locations (México, Ecuador, Peru, and within Ecuador) is consistent with presence of a single yellowfin tuna population within the EPO. Our findings are consistent with the IATTC assessment and provide further evidence of the need for transboundary cooperation for the successful management of this important fishery throughout the EPO.

Behavioral Responses of the Common Bed Bug to Essential Oil Constituents.

Botanical-derived pesticides have arisen as an attractive alternative to synthetic insecticides to effectively manage infestations of bed bugs (Cimex lectularius L.). While information on contact, residual, and fumigant toxicity of plant-essential oils against bed bugs have been recently published, there is a gap of information regarding the repellent activity of these products and their constituents. Identification of essential oil constituents (EOCs) with repellent activity will help develop potentially efficacious essential oil-based formulations for use in bed bug management programs. In this study, we first screened fresh and 24 h-aged residues of geraniol, eugenol, carvacrol, thymol, citronellic acid, linalool, menthone, trans-cinnamaldehyde, α-pinene, ß-pinene, and limonene for avoidance behavior from individual bed bugs with a video-tracking system. Six EOCs, geraniol, eugenol, citronellic acid, thymol, carvacrol, and linalool were further evaluated overnight in choice tests to determine whether 24-h aged residues were still avoided by groups of bed bugs. While bed bugs avoided resting on filter papers treated with 24-h aged residues of geraniol, eugenol, citronellic acid, and carvacrol, bed bugs aggregated in areas treated with linalool-aged residues. Barriers of EOCs did not prevent bed bugs from reaching a warmed blood source and acquiring blood meals. Our results show that novel formulations of natural product insecticides that include geraniol, eugenol, carvacrol, or citronellic acid have potential to repel bed bugs. The presence of host-associated cues might interfere with these responses.