Skating on thin ice: Identifying the need for species‐specific data and defined migration ecology of Rajidae spp.

Skates (class Chondrichthyes; subclass Elasmobranchii; order Rajiformes; family Rajidae) comprise one quarter of extant chondrichthyans, yet have received little attention in the scientific literature likely due to their relatively low economic value and difficulties in species identification. The absence of species‐specific information on catch, life history and migration of skates has often precluded the development of single‐species stock assessments and led to the use of cursory multispecies assessments, which lack the ability to track species‐specific catch and abundance trends. This has resulted in undetected local extirpations, as has been previously reported for common (Dipturus batis, Rajidae), white (Rostroraja alba, Rajidae) and long‐nose (Dipturus oxyrhinchus, Rajidae) skates in the Irish Sea. Here, we (a) use case studies to illustrate how the perception of skate population structure and stock status has historically been masked through multispecies assessment and management practices, (b) review current information on the movement of skates and identify gaps in knowledge, and (c) identify biases associated with the use of various tagging technologies, which have confounded our understanding of movement and migration ecology of skates. Considering that over 40% of extant Rajidae species are listed as “Data Deficient” by the International Union for Conservation of Nature, we illustrate a critical need to broaden the current understanding of skate life history, movement and migration ecology by providing recommendations on the further application of electronic tags and biogeochemical natural tags in movement studies and highlight the benefits that studies using these approaches have for novel management frameworks.     

Using acoustic telemetry and snorkel surveys to study diel activity and seasonal migration of round goby (Neogobius melanostomus) in an estuary of the Western Baltic Sea

In just two decades, round goby Neogobius melanostomus (Pallas) has dispersed throughout most of the Baltic and the North American Great Lakes. It thrives in shallow sheltered areas, where it is impacting native fauna. In Denmark, researchers, governmental institutions and fishers have joined in an effort to establish a sustainable round goby fishery. To do so, basic information about the movement of round goby is essential, so the movements of 50 round gobies were tracked using acoustic telemetry. The results revealed that activity took place mainly at night and seasonal migrations were common. The most frequent migration behaviour observed was a seaward return migration during winter, which was further confirmed by a snorkel survey. Tracking data also revealed riverine upstream dispersal. The results demonstrate that the round goby can be mapped using telemetry, and it is suggested that fishing for round goby may improve efficiency by targeting seasonal migration corridors.     

Designing satellite tagging studies: estimating and optimizing data recovery

Satellite telemetry is used routinely to collect and transmit movement, behaviour and environmental data from free‐ranging animals. Satellite tags (hereafter SATs) are essential for collecting in situ data from animals where manual retrieval of a data logger is impossible. The collected data is fundamental for scientific and many management applications. However, the amount of data a SAT can transmit is limited by its battery life, transmission opportunities, bandwidth and satellite coverage. When designing a SAT study, these factors should be taken into account to ensure that limited transmissions are utilized as effectively as possible. In this paper we present a theoretical discussion of the factors that influence the data transmission and present tools for designing effective SAT studies. We calculate the optimal sampling period for the tag given its expected lifetime and regional variation in satellite coverage. Taking these factors into account allows prediction of the expected number of tags required to meet targets for a deployment. These methods are applied to a case study of a highly migratory pelagic fish tagged with popup archival satellite tags (PSATs). Our findings will be useful for SAT study design in general and demonstrate an approach which can reduce the ad hoc nature of SAT deployments.     

High variability in spawning migration of sea trout,Salmo trutta,in two northern Swedish rivers

Abstract Telemetry was used to examine spawning migration of sea trout, Salmo trutta L. (n = 126), in two rivers in northern Sweden. The spawning areas defined by radio‐tagged fish differed between the river systems. In the River Vindelälven, sea trout spawned in the main stem and 80% of tagged individuals returned to areas where hatchery‐reared juveniles had been previously stocked. In the River Piteälven, 74% of tagged sea trout ascended tributaries for spawning. Tagged fish were categorised into three groups of migratory pattern. cart (classification and regression tree) analysis indicated that distance from tagging location to spawning site (S_dist) explained the migratory patterns. Large S_dist separated fish with stepwise upstream migration from those with up‐ and downstream migrations and one‐directional direct migration. Fish tagged early in the season migrated the longest distance to spawning areas. Stocking locations and sex explained the large search behaviour up‐ and downstream in the rivers. The findings are important for the sustainable management of sea trout in the Gulf of Bothnia.     

激活标签法及其在番茄功能基因组的应用

激活标签法是近年来新发展起来的一种研究基因功能有价值的补充方法。该文综述了激活标签法的研究进展及其在番茄功能基因组研究中的应用。     

Molecular genetic characterisation of the Asc locus of tomato conferring resistance to the fungal pathogen Alternaria alternata f. sp. lycopersici

The Alternaria stem canker disease of tomato is caused by the fungal pathogen Alternaria alternata f. sp. lycopersici and its host-selective AAL-toxins. Resistance to the pathogen and insensitivity to the toxins are conferred by the Asc locus on chromosome 3L. Sensitivity to AAL-toxins is a relative character; the toxins inhibit development of all tested tomato tissues but susceptible cultivars are much more sensitive than resistant cultivars. In addition to tomato, some other plant and animal species are sensitive to the toxins as well. The likely mode of action of AAL-toxins is interference with sphingolipid biosynthesis by specific inhibition of ceramide synthase activity. To molecularly isolate Asc, transposon tagging and positional cloning strategies are applied. As a first step, transposon insertions and restriction fragment length polymorphism (RFLP) markers are identified in proximity of the Asc locus. Subsequently, the transposons are used to inactivate Asc by insertion mutagenesis, and the RFLP markers are used to identify yeast artificial chromosomes (YACs) with tomato DNA inserts. Once an Asc-insertion mutant and/or a YAC encompassing Asc has been obtained, physical isolation and characterisation of Asc will be conceivable. Elucidation of the molecular role of Asc will illuminate the specificity of host recognition by Alternaria alternata f. sp. lycopersici.Abbreviations AAL-toxin Alternaria alternata lycopersici-toxin - A. a. lycopersici Alternaria alternata f. sp. lycopersici - Asc Alternaria stem canker - HST host-selective toxin     

A random amplified polymorphic DNA (RAPD) molecular marker for the Tm-2 a gene in tomato

Summary A RAPD marker, linked to the Tm-2 ^agene engendering TMV resistance in tomatoes, was identified. The validity of the RAPD marker was corroborated by screening several tomato varieties, and correctly identifying those which carried Tm-2 ^a, as well as by F₂ segregation analysis. All tested resistant varieties descending from a common Lycopersicon peruvianum/esculentum ancestor, LA1791, exhibited this marker.     

Methods for studying spatial behaviour of freshwater fishes in the natural environment

Spatial behaviour of fishes in fresh and brackish water ranges in temporal scales between localized diel movements, often associated with foraging and predator evasion, to seasonal or life‐cycle related events involving movements between freshwater habitats or freshwater and marine biotopes. Recent technological advances have resulted in dramatic improvements in the range of techniques available for the study of spatial behaviour of freshwater fishes in the natural environment, and broadly may be divided into two categories: capture dependent and capture independent. The former incorporates those methods that rely on sampling marked fish (mark–recapture) or unmarked fish (density estimates, catch per unit effort) over defined scales of time and space in order to derive information on distribution and movement. Captured fish may also be tagged with transmitters that radiate energy, enabling the fish to be tracked and/or environmental data to be gathered. Biochemical analysis of samples from fish, requiring non‐destructive sampling (genetic analysis and scale microchemistry) or destructive sampling (otolith microchemistry) may also provide information on migration and ontogenetic processes. Capture independent techniques include visual observation and video techniques, hydroacoustics and automated fish counting. Catch per unit effort and mark–recapture techniques are most efficient where long‐term fishery or monitoring studies are in place and data on crude spatial and temporal scales are acceptable. They also have the advantages of low technical requirements and low equipment costs. Where specific management or ecological questions are pertinent, recapture independent techniques may be more appropriate. Telemetric methods can provide high resolution information at the individual level, while hydroacoustics is increasingly providing information at the population level in large lake and river environments. Biochemical methods are becoming increasingly useful in determining the extent of population segregation, where DNA analysis is used, and in the study of migration and ontogenetic changes in behaviour, where otolith microchemistry and stable isotope analysis is used.     

草鱼标志技术的初步研究

采用切鳍法和挂牌法对体长为11～17cm、体重50～70g的草鱼（Ctenopharyngodon idellus）进行标志研究,用铜丝从背鳍第一与第二支鳍骨间缝隙穿过,将椭圆型塑料标牌（长8mm×宽5mm×厚1mm）挂在背鳍基前,标志牌及铜丝的平均总重量为0.04g,不影响草鱼正常游泳和摄食等活动;暂养10d的标志牌保持率达到82.4%,土塘饲养70d的成活率为91.5%,标记保持率为79.9%。切鳍法标记草鱼暂养10d后,标志保持率100%,土塘饲养70d后,成活率为83.6%,80.7%的草鱼被剪鳍条已完全或接近完全再生,标记保持率只有19.3%。挂牌标记比切鳍法标记的成活率高7.9%。需要2周时间进行食性转化训练,将饲料食性转回天然食性即草食性。研究结果显示,切鳍法因切除的腹鳍可以完全再生,只适合短期标志（约30d）;挂牌法具有较高的标志保持率、标牌保留时间较长和标牌醒目等特点,可用于较长时间的试验研究。2种标志方法均可应用于草鱼增殖放流的效果评估。     

Habitat utilization and vertical movements of white marlin (Tetrapturus albidus) released from commercial and recreational fishing gears in the western North Atlantic Ocean: inferences from short duration pop-up archival satellite tags

Researchers have applied numerous techniques to improve billfish stock assessments, including habitat‐based models that incorporate behavioral and oceanographic parameters to standardize historical catch‐per‐unit‐effort time‐series data. These methods have allowed researchers to account for significant changes in the depths of pelagic longline (PLL) gear deployments over time. This study presents habitat‐use data recovered from high‐resolution 5‐ and 10‐day pop‐up satellite archival tags (PSATs) attached to 47 surviving white marlin released from commercial and recreational fishing gears offshore of the U.S. East Coast, the northern Caribbean, and Venezuela between 2002 and 2004. Data recovered from transmitting tags indicated that white marlin spent nearly half of their time associated with warm, near‐surface waters (<10 m). All fish displayed frequent short duration (mean: 39.8 min) vertical excursions from surface waters to depths averaging 51 m. Qualitative and multivariate classifications of data from completely transmitted movements of surviving white marlin revealed two major types of descents: one pattern was characterized by deep ‘V’‐shaped excursions of relatively short duration (mean: 23.4 min) while the other featured descents that were more broadly ‘U’‐shaped and confined to a specific depth range for an extended period of time (mean: 75.8 min). Based on the frequency, persistence, and patterns of these vertical movements, white marlin appear to direct a considerable proportion of foraging effort well below surface waters, a behavior that may account for relatively high catch rates of white marlin on some deep‐set PLL deployments.