Infectious salmon anemia virus (ISAV) is an important pathogen in global Atlantic salmon (Salmo salar L.) aquaculture. The existence of both non-pathogenic (ISAV-HPR0) and pathogenic (HPR-deleted ISAV) forms of the virus impacts hatchery management. In November 2016, fish tested positive for ISAV-HPR0 at the National Cold Water Marine Aquaculture Center in Maine. A cohort exposed to the fish testing positive for ISAV were lethally sampled over a 7-month period (February–August 2017). No positive samples were detected during this time. Additional testing aimed to determine the extent of the ISAV infections in the facility’s fish and to investigate the water sources as potential virus entry points. Fish testing was designed to detect 2% pathogen prevalence with 95% confidence (assuming diagnostic sensitivity of 85%). Over a three-year period, ISAV-HPR0 was detected in spawning fish annually and once in smolts. Repeat testing of smolts from the affected tank three weeks later failed to detect ISAV-HPR0. Over a one-year period of weekly or biweekly evaluation of the incoming water sources, ISAV was never detected. These findings suggest that ISAV-HPR0 infections in monitored hatchery populations can evade detection and that episodes of high prevalence of ISAV-HPR0 associated with spawning can be highly transient. In both cases, conventional surveillance based on recurrent testing of healthy populations may provide only a very limited indication of the HPR0 status. Instead, targeting surveillance to periods of physiological stress, such as spawning and smoltification, and adjusting the sample sizes to account for a related surge in prevalence, should enhance the detection capacity in hatchery settings while also reducing testing costs.

The potential for infectious salmon anemia virus (ISAV)—an internationally regulated pathogen of salmon—to transmit vertically from parent to offspring is currently unclear. While the highly virulent ISAV phenotype known as ISAV-HPRΔ has been observed intra-ova, evidence for vertical transmission of the avirulent ISAV phenotype known as ISAV-HPR0 is lacking. In this study, we identified ISAV-HPR0-infected Atlantic salmon broodstock during spawning within a government research recirculating aquaculture facility using qPCR. Eggs and milt from infected brood were used to initiate 16 unique family dam-sire crosses from which 29–60 fertilized eggs per cross were screened for ISAV using qPCR (limit of detection ~100 virus genome copies/egg). A portion of eggs (~300) from one family cross was hatched and further reared in biosecure containment and periodically screened for ISAV by gill clipping over a 2-year period. ISAV was not detected in any of the 781 eggs screened from 16 family crosses generated by infected brood, nor in 870 gill clips periodically sampled from the single-family cohort raised for 2 years in biocontainment. Based on these findings, we conclude that ISAV-HPR0 has a limited likelihood for vertical parent-to-offspring transmission in cultured Atlantic salmon.

Geosmin and 2-methylisoborneol are volatile organic compounds of microbial origin that frequently occur in recirculating aquaculture systems and confer unpleasant odors and flavors to fish therein, even at extremely low concentrations. Existing analytical methods for these compounds in fish struggle to achieve enough sample throughput and are oftentimes not automated, requiring extensive hands-on preparation. We have developed methods for analyzing geosmin and 2-methylisoborneol from water and fish tissues, respectively, using a metal probe bearing a high-capacity sorptive extraction phase. A robust and quantitative detection was achieved from both water and fish tissues, with minimum detection limits of 1.2 ng/L for geosmin and 1.1 ng/L for 2-methylisoborneol from water and 18.1 ng/kg and 13.6 ng/kg, respectively, from fish tissue. These concentrations were well below human detection thresholds. Hence, we concluded that these methods could detect geosmin and 2-methylisoborneol before they became perceptible to humans. In contrast to other high-capacity sorptive extraction techniques, such as stir-bar sorptive extraction, this technique is fully automatable, dramatically improving throughput and precluding manual handling errors, while the durable design of the probe precludes breakage, such as is common with solid phase microextraction (SPME) fiber. This method is suitable for odorant monitoring in all water quality settings, as well as for the detection of off-flavor compounds in solid and semi-solid matrices.

La caza de ciervos es un atributo cultural importante que contribuye a la economía de los Estados Unidos. Varios estados ofrecen oportunidades para cazar machos con astas, algunos a principios de septiembre, cuando los machos pueden retener el terciopelo en las astas. El terciopelo de la asta indica el crecimiento de esta que se produce anualmente en el venado cola blanca macho (Odocoileus virginianus). El desprendimiento de terciopelo ocurre durante finales de agosto y septiembre, pero este período no se ha descrito formalmente en poblaciones silvestres de los Estados Unidos. En este documento, establecimos un punto de referencia para el comienzo de la muda de terciopelo en el venado cola blanca en el centro de Nebraska y comparamos la muda entre machos de diferentes edades. Este estudio utilizó cámaras trampa en áreas con ciervos en bosques ribereños a lo largo de los ríos Platte y Loup. La muda de terciopelo tomó alrededor de 35 días y el 95% del desprendimiento ocurrió antes del 17 de septiembre. La primera observación de muda de terciopelo ocurrió el 22 de agosto, mientras que, la última observación de terciopelo retenido en las astas fue el 25 de septiembre. El porcentaje de ciervos con muda de terciopelo difirió entre dos grupos de edad a lo largo del tiempo (P < 0.01), los machos ≥2.5 años mudaron el terciopelo de sus astas un 13% antes en promedio en comparación con los machos de 1.5 años. Hasta donde conocemos, estos hallazgos representan la primera fenología de muda de astas documentada, de una población salvaje de venados cola blanca en los Estados Unidos. Nuestros hallazgos sirven como base para las comparaciones espaciales y temporales entre los estados y pueden ser utilizados por los administradores y las agencias de vida silvestre a medida que evalúan las regulaciones para cazar ciervos durante las primeras temporadas de caza.

Antlers are genetically coded to have bilateral symmetry. However, environmental stressors cause asymmetries between antlers. Previous studies have investigated fluctuating asymmetries on harvested white-tailed deer (Odocoileus virginianus Zimmermann, 1780). Cast antlers provide underutilized metrics that are not available prior to shedding. The objectives of this study were to quantify relative fluctuating asymmetry (RFA) between age groups and identify the best age-specific pre- and post-cast antler metrics to confirm an antler pair. We hypothesized lower RFA values for post-cast measurements than pre-cast measurements due to a lessened chance for damage when atop the head. Additionally, younger individuals were hypothesized to have higher RFA values due to greater susceptibility to environmental stressors. Cast antler pairs from 196 white-tailed deer were collected in Nebraska. We measured 14 available antler metrics per cast antler side classified by age group. The most symmetric measurements between antler sides included pedicle seal area, main beam length, and circumference. Antlers of older deer were consistently more symmetric than younger deer. When combining the top metrics and testing against random antler pairs, we found an 81.9–92.3% match rate for 1.5 and ≥2.5-year-olds, respectively. Our findings provided a quantifiable method to assign antler pair classifications more confidently while documenting decreased symmetry in younger individuals.