Squalus Acanthias Research Articles

In situ method for the determination of nutrient acquisition and its hormonal regulation in the spiral valve of two chondrichthyan fishes.

Chondrichthyans play an important role in nutrient cycling of many marine ecosystems, yet little is known about their nutritional physiology particularly relating to nutrient acquisition in the spiral valve intestine. This unique organ poses challenges for examining nutrient transport physiology using traditional reductionist methods owing to its scroll-like morphology. Thus, we established a method for the characterization of nutrient uptake rates in two representative chondrichthyans, the Pacific spiny dogfish (Squalus suckleyi) and the Pacific spotted ratfish (Hydrolagus colliei). We validated a dual-cannulation method wherein perfusate was circulated through the vasculature of the spiral valve via the anterior and posterior intestinal arteries, and [14C]glucose or [3H]oleic acid was accumulated from the static spiral valve lumen into the anterior and posterior intestinal veins. Radiotracer accumulated at a stable rate in the venous effluent in comparison with measures of mucosal disappearance. Interestingly, similar anterior and posterior glucose uptake was observed in dogfish, yet significantly more oleic acid was accumulated in the posterior veins of ratfish. Further validation of the preparation in dogfish demonstrated sodium dependence of glucose transport as well as an effect of bovine insulin administration to the arterial circulation. Each of these manipulations resulted in significant differences in glucose handling between the anterior and posterior veins, suggestive of heretofore unknown heterogenous functions along the intestine. This preparation demonstrates a new and reliable method for the measurement of nutrient acquisition and regulation thereof in a unique digestive organ. Furthermore, it presents avenues for investigation of differential functional along the spiral valve.NEW & NOTEWORTHY We describe a novel dual cannulation method for investigating radiolabeled nutrient uptake from a unique organ, the spiral valve. Furthermore, we identify functional differences in nutrient transport along the length of the spiral valve which consists of a homogenous gross morphology. Finally, this method reveals a useful way in which to manipulate the arterial supply to better understand postprandial physiology as it varies with metabolites and endocrine factors.

Integrating survey and observer data improves the predictions of New Zealand spatio-temporal models

AbstractIn many situations, species distribution models need to make use of multiple data sources to address their objectives. We developed a spatio-temporal modelling framework that integrates research survey data and data collected by observers onboard fishing vessels while accounting for physical barriers (islands, convoluted coastlines). We demonstrated our framework for two bycatch species in New Zealand deepwater fisheries: spiny dogfish (Squalus acanthias) and javelinfish (Lepidorhynchus denticulatus). Results indicated that employing observer-only data or integrated data is necessary to map fish biomass at the scale of the New Zealand exclusive economic zone, and to interpolate local biomass indices (e.g., for the east coast of the South Island) in years with no survey but available observer data. Results also showed that, if enough survey data are available, fisheries analysts should: (1) develop both an integrated model and a model relying on survey-only data; and (2) for a given geographic area, ultimately choose the index produced with integrated data or the index produced with survey-only data based on the reliability of the interannual variability of the index. We also conducted a simulation experiment, which indicated that the predictions of our spatio-temporal models are virtually insensitive to the consideration of physical barriers.

An adapted liver perfusion in a shark species, Squalus suckleyi: investigation of energy mobilization.

The liver is an essential energy storage organ in vertebrates. In teleosts and elasmobranchs, previous studies examining hepatic energy balance have used isolated hepatocytes. Although these studies have been informative, the high-fat content in the elasmobranch liver limits isolation of hepatocytes and therefore the utility of this method to understand hepatic metabolic processes. In the present study, we developed an in situ liver perfusion in the North Pacific spiny dogfish Squalus suckleyi. Perfusions were conducted by cannulating the hepatic portal vein (inflowing cannulation) and the sinus venosus through the heart (outflowing cannulation). Changes in major elasmobranch metabolites (glucose and 3-hydroxybutarate [3-HB]) were determined by the arterial (inflow)-venous (outflow) difference in metabolite concentration. Liver preparations were considered viable due to consistent oxygen consumption over 3 h and the maintenance of predictable vasoconstriction following administration of homologous 10-7 M angiotensin II (ANG II). Removal and reintroduction from the perfusate of metabolites showed endogenous 3-HB production in the isolated perfused livers but did not affect glucose balance. However, the arterial-venous difference of both metabolites did not change following perfusion with heterologous insulin and homologous glucagon, which may be due to the glucose intolerant nature of elasmobranchs. Ultimately, we show the viability of this perfusion for the investigation of hepatic energy mobilization in sharks.NEW & NOTEWORTHY We describe a viable liver perfusion in a shark species for the first time as determined by oxygen consumption and hormone-mediated changes in hemodynamics (angiotensin II, ANG II). In addition, removal of major energy metabolites confirms hepatic ketone [3-hydroxybutyrate (3-HB)] production by an elasmobranch liver. Perfusion with heterologous insulin and homologous glucagon did not cause changes in glucose balance, however, possibly demonstrating differences in glucose metabolism in this taxon as compared with more derived vertebrates.

Laterality defect of the heart in non-teleost fish.

Dextrocardia is a rare congenital malformation in humans in which most of the heart mass is positioned in the right hemithorax rather than on the left. The heart itself may be normal and dextrocardia is sometimes diagnosed during non-related explorations. A few reports have documented atypical positions of the cardiac chambers in farmed teleost fish. Here, we report the casual finding of a left-right mirrored heart in an 85 cm long wild-caught spiny dogfish (Squalus acanthias) with several organ malformations. Macroscopic observations showed an outflow tract originating from the left side of the ventricular mass, rather than from the right. Internal inspection revealed the expected structures and a looped cavity. The inner curvature of the loop comprised a large trabeculation, the bulboventricular fold, as expected. The junction between the sinus venosus and the atrium appeared normal, only mirrored. MRI data acquired at 0.7 mm isotropic resolution and subsequent 3D-modeling revealed the atrioventricular canal was to the right of the bulboventricular fold, rather than on the left. Spurred by the finding of dextrocardia in the shark, we revisit our previously published material on farmed Adriatic sturgeon (Acipenser naccarii), a non-teleost bony fish. We found several alevins with inverted (left-loop) hearts, amounting to an approximate incidence of 1%-2%. Additionally, an adult sturgeon measuring 90 cm in length showed abnormal topology of the cardiac chambers, but normal position of the abdominal organs. In conclusion, left-right mirrored hearts, a setting that resembles human dextrocardia, can occur in both farmed and wild non-teleost fish.

Effect of parabranchial position on ventilatory pressures in the Pacific spiny dogfish (Squalus suckleyi)

The mechanics of ventilation in elasmobranchs have been described as a two-pump system which is dependent on the generation of differential pressures between the orobranchial and parabranchial cavities. However, this general model does not take into account sources of variation in parabranchial form and function. For example, the relative pressures that drive flow in each parabranchial chamber during ventilation remain largely unexplored. To address this gap, parabranchial pressures were collected from the Pacific spiny dogfish (Squalus suckleyi, n = 12) during routine ventilation using transducers inserted into parabranchial chambers 2, 3, and 5, numbered anteriorly to posteriorly. Pressure amplitudes collected from the three chambers displayed an attenuation of pressure amplitudes posteriorly, as well as differential, modular use of parabranchial chamber five These observations have implications for the functioning of the ventilatory pump and indicate distinct ventilatory modes, leading us to propose a new model to describe ventilation in Squalus suckleyi.

Molecular and pharmacological analysis of the melanocortin-2 receptor and its accessory proteins Mrap1 and Mrap2 in a Squalomorph shark, the Pacific spiny dogfish

The hypothalamus–pituitary–adrenal/interrenal (HPA/I) axis is a conserved vertebrate neuroendocrine mechanism regulating the stress response. The penultimate step of the HPA/I axis is the exclusive activation of the melanocortin-2 receptor (Mc2r) by adrenocorticotropic hormone (ACTH), requiring an accessory protein, Mrap1 or Mrap2. Limited data for only three cartilaginous fishes support the hypothesis that Mc2r/Mrap1 function in bony vertebrates is a derived trait. Further, Mc2r/Mrap1 functional properties appear to contrast among cartilaginous fishes (i.e., the holocephalans and elasmobranchs). This study sought to determine whether functional properties of Mc2r/Mrap1 are conserved across elasmobranchs and in contrast to holocephalans. The deduced amino acid sequences of Pacific spiny dogfish (Squalus suckleyi; pd) pdMc2r, pdMrap1, and pdMrap2 were obtained from a de novo transcriptome of the interrenal gland and validated against the S. suckleyi genome. pdMc2r showed high primary sequence similarity with elasmobranch and holocephalan Mc2r except at extracellular domains 1 and 2, and transmembrane domain 5. pdMraps showed similarly high sequence similarity with holocephalan and other elasmobranch Mraps, with all cartilaginous fish Mrap1 orthologs lacking an activation motif. cAMP reporter gene assays demonstrated that pdMc2r requires an Mrap for activation, and can be activated by stingray (sr) ACTH(1–24), srACTH(1–13)NH2 (i.e., α-MSH), and γ-melanocyte-stimulating hormone at physiological concentrations. However, pdMc2r was three orders of magnitude more sensitive to srACTH(1–24) than srACTH(1–13)NH2. Further, pdMc2r was two orders of magnitude more sensitive to srACTH(1–24) when expressed with pdMrap1 than with pdMrap2. These data suggest that functional properties of pdMc2r/pdMrap1 reflect other elasmobranchs and contrast what is seen in holocephalans.

Characteristics of the spiny dogfish (Squalus acanthias) nuclear genome.

Sequenced shark nuclear genomes are underrepresented, with reference genomes available for only four out of nine orders so far. Here, we present the nuclear genome, with annotations, of the spiny dogfish (Squalus acanthias), a shark of interest to biomedical and conservation efforts, and the first representative of the second largest order of sharks (Squaliformes) with nuclear genome annotations available. Using Pacific Biosciences Continuous Long Read data in combination with Illumina paired-end and Hi-C sequencing, we assembled the genome de novo, followed by RNA-Seq-supported annotation. The final chromosome-level assembly is 3.7 Gb in size, has a BUSCO completeness score of 91.6%, and an error rate of less than 0.02%. Annotation predicted 33,283 gene models in the spiny dogfish's genome, of which 31,979 are functionally annotated.

"A prized Pacific shark": the rise and fall (and rise again…?) of the world's first ecolabel certified sustainable shark fishery.

There is intense public interest surrounding the conservation and management of sharks, including a debate over whether sustainable shark fisheries are possible or fishing bans on sharks are needed to conserve these animals. An important but rarely discussed datapoint in discussions of global shark fisheries is the case of British Columbia's fishery for Pacific spiny dogfish, Squalus suckleyi, which in 2011 became the first Marine Stewardship Council certified shark fishery anywhere in the world. A few years later, despite reportedly healthy local stocks and thriving global markets for this shark, the fishery voluntarily withdrew their MSC certification, and in recent years more than 95% of the quota for Pacific spiny dogfish has been left in the water. This study provides insight into what happened to this fishery through a review of grey literature and a series of stakeholder interviews with British Columbian fishermen, fish processors, managers, and environmentalists. It is a rare case study of a fishery that largely ceased operations without a clear mechanistic explanation like a stock collapse, a government mandate to limit fishing, or a clear shift in market demand. This fishery appears to have been affected by the combination of several factors, including a temporary reduction in biomass due to oceanographic effects, potential blowback from overly broad environmental messaging that didn't distinguish between sustainable and unsustainable shark fisheries, management changes resulting in altered fishing incentives, and changes to processing capacity associated with consolidating the fishing industry into ownership by relatively few large companies. This article is protected by copyright. All rights reserved.

Spatially varying catchability for integrating research survey data with other data sources: case studies involving observer samples, industry-cooperative surveys, and predators as samplers

Spatio-temporal models are widely applied to standardise research survey data and are increasingly used to generate density maps and indices from other data sources. We developed a spatio-temporal modelling framework that integrates research survey data (treated as a “reference dataset”) and other data sources (“non-reference datasets”) while estimating spatially varying catchability for the non-reference datasets. We demonstrated it using two case studies. The first involved bottom trawl survey and observer data for spiny dogfish ( Squalus acanthias) on the Chatham Rise, New Zealand. The second involved cod predators as samplers of juvenile snow crab ( Chionoecetes opilio) abundance, integrated with industry-cooperative surveys and a bottom trawl research survey in the eastern Bering Sea. Our integrated models leveraged the strengths of individual data sources (the quality of the reference dataset and the quantity of non-reference data), while downweighting the influence of the non-reference datasets via the estimated spatially varying catchabilities. They allowed for the generation of annual density maps for a longer time-period and for the provision of one single index rather than multiple indices each covering a shorter time-period.

Using 15N to determine the metabolic fate of dietary nitrogen in North Pacific spiny dogfish (Squalus acanthias suckleyi).

Marine elasmobranchs are ureosmotic, retaining large concentrations of urea to balance their internal osmotic pressure with that of the external marine environment. The synthesis of urea requires the intake of exogenous nitrogen to maintain whole-body nitrogen balance and satisfy obligatory osmoregulatory and somatic processes. We hypothesized that dietary nitrogen may be directed toward the synthesis of specific nitrogenous molecules in post-fed animals; specifically, we predicted the preferential accumulation and retention of labelled nitrogen would be directed towards the synthesis of urea necessary for osmoregulatory purposes. North Pacific spiny dogfish (Squalus acanthias suckleyi) were fed a single meal of 7 mmol l-1 15NH4Cl in a 2% ration by body mass of herring slurry via gavage. Dietary labelled nitrogen was tracked from ingestion to tissue incorporation and the subsequent synthesis of nitrogenous compounds (urea, glutamine, bulk amino acids, protein) in the intestinal spiral valve, plasma, liver and muscle. Within 20 h post-feeding, we found labelled nitrogen was incorporated into all tissues examined. The highest δ15N values were seen in the anterior region of the spiral valve at 20 h post-feeding, suggesting this region was particularly important in assimilating the dietary labelled nitrogen. In all tissues examined, enrichment of the nitrogenous compounds was sustained throughout the 168 h experimental period, highlighting the ability of these animals to retain and use dietary nitrogen for both osmoregulatory and somatic processes.

High reproductive potential of the commercially exploited shark Squalus suckleyi in the major fishing grounds of the western North Pacific.

The present study examined body length (precaudal length, PCL) and age at sexual maturity, as well as fecundity and maternal investment in the Pacific spiny dogfish Squalus suckleyi, a long-term commercially exploited shark in the western North Pacific, using samples caught in several fisheries and across seasons. The PCL and age at 50% sexual maturity of males were 60.6 cm and 9.4 years, respectively; and those of females were 73.1 cm and 17.8 years, respectively. The PCL and age at 50% maternity were 77.4 cm and 19.7 years, respectively. General or generalised linear models revealed that the fishing method was not significantly correlated with sexual maturity (both sexes), and the maternity rate and litter size were not correlated with female PCL. Other general linear models revealed an increase in offspring size with maternal size, but litter size was not affected by embryonic development. These findings indicate that the reproductive potential of Pacific spiny dogfish is relatively high throughout the whole North Pacific region because of a smaller size and earlier age at sexual maturation in both sexes. In addition, pregnant females displayed no resting phase and produced 0.45 more embryos per cm PCL in their lifetime after the onset of maturity, which is higher than in the eastern North Pacific. We suggest that these qualities are not a consequence of stock decline associated with the long-term exploitation of the species, but that its high reproductive potential has likely contributed to the long-term stability of the landings in Japan. This article is protected by copyright. All rights reserved.

Investigating nitrogen movement in North Pacific spiny dogfish (Squalus acanthias suckleyi), with focus on UT, Rhp2, and Rhbg mRNA abundance.

For ureosmotic marine elasmobranchs, the acquisition and retention of nitrogen is critical for the synthesis of urea. To better understand whole-body nitrogen homeostasis, we investigated mechanisms of nitrogen trafficking in North Pacific spiny dogfish (Squalus acanthias suckleyi). We hypothesized that the presence of nitrogen within the spiral valve lumen would affect both the transport of nitrogen and the mRNA abundance of a urea transporter (UT) and two ammonia transport proteins (Rhp2, Rhbg) within the intestinal epithelium. The in vitro preincubation of intestinal tissues in NH4Cl, intended to simulate dietary nitrogen availability, showed that increased ammonia concentrations did not significantly stimulate the net uptake of total urea or total methylamine. We also examined the mRNA abundance of UT, Rhp2, and Rhbg in the gills, kidney, liver, and spiral valve of fasted, fed, excess urea fed, and antibiotic-treated dogfish. After fasting, hepatic UT mRNA abundancewas significantly lower, and Rhp2 mRNA in the gills was significantly higher than the other treatments. Feeding significantly increased Rhp2 mRNA levels in the kidney and midspiral valve region. Both excess urea and antibiotics significantly reduced Rhbg mRNA levels along all three spiral valve regions. The antibiotic treatment also significantly diminished UT mRNA abundance levels in the anterior and midspiral valve, and Rhbg mRNA levels in the kidney. In our study, no single treatment had significantly greater influence on the overall transcript abundance of the three transport proteins compared to another treatment, demonstrating the dynamic nature of nitrogen balance in these ancient fish.

Spatio‐temporal model and machine learning method reveal patterns and processes of migration under climate change

AbstractAimDespite extensive studies of phenological shifts in migration by climate change and driving factors of migration, a few issues remain unresolved. In particular, little is known about the complex effects of driving factors on migration with interactions and nonlinearity, and partitioning of the effects of factors into spatial, temporal, and spatio‐temporal effects. Here, we aim to elucidate migration pattern as well as its driving factors under climate change.LocationWestern North Pacific.TaxonNorth Pacific spiny dogfish Squalus suckleyi.MethodsWe first examined long‐term changes in the timing and geographic location of migration by applying the Barrier model, a spatio‐temporal model, to c. 5‐decade time series data (1972–2019) for the presence/absence of spiny dogfish in the western North Pacific. We then evaluated the spatial, temporal and spatio‐temporal effects of driving factors (fish productivity, sea surface temperature [SST], depth and magnetic field) on seasonal occurrence patterns using a machine learning model and an interpretable machine learning technique.ResultsThe migration area did not change over c. 5‐decades, whereas the migration timing advanced by a month after 2000. The spatial effects of magnetic field and depth were consistently large and the spatial and spatio‐temporal effects of SST increased in the migration season, even though the temporal effect of SST was consistently weak.Main ConclusionsThe migration area of spiny dogfish was stable over time because of the effect of magnetic field and a strong preference for submarine topography, whereas the migration timing advanced as a result of tracking a suitable location based on SST, which increased sharply after 2000. Therefore, temperature and other factors simultaneously influence migration under climate change, highlighting the importance of considering both biotic and abiotic factors and understanding the underlying processes in predicting future impacts of climate change on species distribution.

Development and parameterization of a data likelihood model for geolocation of a bentho-pelagic fish in the North Pacific Ocean

State-space geolocation models feature coupled process (movement) and observation (data likelihood) models to reconstruct fish movement trajectories using electronic tag data. Development of the data likelihood model is therefore a key step in adapting a state-space geolocation model for use with different fish species, geographical regions, or types of electronic data. Here we adapt a discrete hidden Markov model for the geolocation of Pacific spiny dogfish (Squalus suckleyi, n = 154) in the North Pacific Ocean by developing a data likelihood model based on Microwave Telemetry X-tag Pop-up Satellite Archival Tag (PSAT) data. The data likelihood model consists of light-based longitude, light-based latitude, sea surface temperature (SST), temperature-depth profile (TDP), and maximum daily depth. Pacific spiny dogfish tend to occupy coastal waters where small-scale local currents and freshwater inputs make SST and TDP variables difficult to map. To address this issue, we introduce an empirical method for parameterizing SST and TDP likelihoods by calculating root mean square difference between PSAT temperature and depth values recorded at known locations (day of tag deployment and tag pop-up) and mapped values at those locations. For SST observations (n = 85), the difference between measured and mapped values did not vary seasonally or monthly and the overall root mean square error (RMSE) used to parameterize the SST likelihood was 0.9 °C. Likelihood values for SST at known locations were higher for likelihoods parameterized with the empirical value compared to variance specification methods from previous studies. For TDP, measured values differed from mapped values (n = 89) by depth, season, and month. Therefore, RMSE values used to parameterize the TDP likelihood were calculated for each depth bin (n = 27) and month. RMSE values were low (< 1 °C) for all depths during the winter but increased for depths < 100 m during the summer months. Our work provides an example of adapting state-space geolocation models for specific applications. It demonstrates the value of large numbers of tagged animals for parameterizing the data likelihood model in coastal waters as well as flexible data likelihood models with component likelihoods that can be switched on or off depending on geolocation quality.

The effect of temperature on haemoglobin-oxygen binding affinity in regionally endothermic and ectothermic sharks.

Haemoglobin (Hb)-O2 binding affinity typically decreases with increasing temperature, but several species of ectothermic and regionally endothermic fishes exhibit reduced Hb thermal-sensitivity. Regionally endothermic sharks, including the common thresher shark (Alopias vulpinus) and lamnid sharks such as the shortfin mako shark (Isurus oxyrinchus), can maintain select tissues and organs warmer than ambient temperature by retaining metabolic heat with vascular heat exchangers. In the ectothermic bigeye thresher shark (Alopias superciliosus), diurnal movements above and below the thermocline subject the tissues, including the blood, to a wide range of operating temperatures. Therefore, blood-O2 transport must occur across internal temperature gradients in regionally endothermic species, and over the range of environmental temperatures encountered by the ectothermic bigeye thresher shark. While previous studies have shown temperature-independent Hb-O2 affinity in lamnid sharks, including shortfin mako, the Hb-O2 affinity of the common and bigeye thresher sharks is unknown. Therefore, we examined the effect of temperature on whole blood Hb-O2 affinity in common thresher shark and bigeye thresher shark. For comparison, analyses were also conducted on the shortfin mako shark and two ectothermic species, blue shark (Prionace glauca) and spiny dogfish (Squalus acanthias). Blood-O2 binding affinity was temperature-independent for common thresher shark and shortfin mako shark, which should prevent internal temperature gradients from negatively affecting blood-O2 transport. Blue shark and spiny dogfish blood-O2 affinity decreased with increasing temperature, as expected, but bigeye thresher shark blood exhibited both a reduced temperature-dependence and a high Hb-O2 affinity, which likely prevents large changes in environment temperature and low environmental oxygen from affecting O2 uptake.

ОЦЕНКА СОСТОЯНИЯ ЗАПАСОВ МОРСКИХ ВИДОВ РЫБ ЧЕРНОГО МОРЯ (ВОДЫ РОССИИ) В 2021 Г

Based on the available biological and fisheries data, stock status review for 18 units of the fish species inhabiting the Black Sea and the both Azov and Black Seas is presented. A modified version of the traditional approach to the harvest control rules for the aquatic bioresources of the Azov and Black Sea Fishery Basin is described for the case when they are assessed by the mathematical methods to estimate the current stock biomass and fishing mortality. For 11 stock units, analytical modeling including cohort, production and trend models has been applied. Based on the estimates of biomass and fishing mortality concerning biological reference points, in 2021, the status of six stock units of the marine fish species inhabiting the basin and exploited by the Russian fisheries was identified as increasing or stable (“Black Sea” stock units of the European sprat and European anchovy, “Crimean” stock unit of turbot, “Crimean and Caucasian” stock unit of red mullet, and “Black and Azov Seas” stock units of garfish and rays). Five fishery stock units (“Crimean and Caucasian” of mullets, picarel and Mediterranean horse mackerel, “Black and Azov Seas” of sand smelts, and “Caucasian” of turbot) have shown a decreasing trend in terms of abundance, and for the rest of the investigated fish stock units (“Mediterranean migrant” bluefish, Atlantic bonito and Atlantic mackerel, “Black Sea” whiting, so-iuy mullet and the other marine fish species, “Black and Azov Seas” spiny dogfish), the status has not been determined due to the absence of systematic biological and fishery data.

Small marine reserves provide conservation benefits for coastal sharks in southern New Zealand

Abstract With the increasingly imperilled status of shark populations, there is a pressing need to evaluate management solutions. Given the threats posed by fishing, marine reserves (MRs) present a promising option. Ata Whenua (Fiordland) in the South Island of Aotearoa/New Zealand is an ideal location to investigate this phenomenon owing to the presence of several shark species in coastal MRs. One‐hundred and sixty‐seven baited remote underwater video deployments were made in five MRs. A multi‐model inference approach using generalized linear modelling was used to assess the combined effect of the MRs on two trophic groups of coastal sharks. Generalized linear modelling was used to assess the effect of protection on, firstly, the presence of broadnose sevengill sharks (Notorynchus cepedianus), while accounting for variations in environmental variables, and secondly, the combined relative abundance of mesopredatory sharks detected (spiny dogfish, Squalus acanthias; school shark, Galeorhinus galeus; and carpet shark, Cephaloscyllium isabellum). Mesopredators had a higher relative abundance in MRs by a factor of 2.5 and there was a strong significant effect of protection, suggesting that MRs have led to an increase in their abundance or a change in distribution. In contrast, there was no effect of protection detected for sevengill sharks. It is concluded that the relatively small (&lt;40 km2) MRs sampled do not provide conservation benefits for a large, mobile shark, but that they are potentially large enough to offer protection for mesopredatory sharks with smaller home ranges. To be effective for shark conservation, we therefore recommend that MRs need to be appropriately sized for the ranging behaviour of the target species for protection.

Mophological description of the parasitic copepod Pandarus boscii (Siphonostomatoida: Pandaridae) found on the Picked dogfish Squalus acanthias (Squaliformes: Squalidae) in Turkish waters

Pandarus boscii was previously reported in Mustelus mustelus (basionym: Squalus mustelus), but the original description of P. boscii was incomplete and inadequate. P. boscii is currently accepted as a synonym of Pandarus bicolor. Females of P. boscii differ in that the body is colorless or pale (in P. bicolor the cephalothorax is brown and the dorsum is yellow), the first and distal segments of the antennule have 23-25 plumose setae and 12 setae, respectively (in P. bicolor are 24-26 plumose setae and 13 setae), mandibular blade with 7-8 teeth (in P. bicolor are 8 teeth), maxilliped with one seta (in P. bicolor absent), proximal exopodal segment of the second leg with 5 spines (in P. bicolor are 6 spines). Significant differences were observed between male individuals of the two species, such as: smaller total body measuring 3.5 mm in length (in P. bicolor 3.9 mm), first and distal segments of the antennule with 15-17 plumose setae and 14 setae, respectively (in P. bicolor 26-27 plumose setae and 12 setae), mandibular blade with 7 teeth (in P. bicolor are 8), first antennal segment with one process and maxilliped with one seta (in P. bicolor absent), leg 5 with one naked and one plumose seta (in P. bicolor 3 plumose setae and a robust seta), distal exopodal segment of 3 and 4 legs with 2 spines (in P. bicolor 4 spines), distal endopodal segment of 3 and 4 legs with 4 and 3 setae, respectively (in P. bicolor with 5 and 4 setae). A detailed description of P. boscii is provided from individuals found on the body surface and fins of the spiny dogfish Squalus acanthias, recently collected in the Sea of Marmara, Turkey. Therefore, according to the results Pandarus boscii and P. bicolor are different species.

Coherence and potential drivers of stock assessment uncertainty in Northeast US groundfish stocks

Abstract Failure to account for the impacts of climate and ecosystem change on stock dynamics can introduce uncertainty to stock assessments that can make meeting the objective of sustainable fisheries management challenging. The increased prevalence and magnitude of uncertainty in New England groundfish stock assessments (i.e. retrospective patterns) in recent years suggest that there may be common drivers impacting these stocks that are currently unaccounted for in the stock assessment. We examined the coherence in retrospective patterns across groundfish stock assessments and evaluated candidate drivers of retrospective patterns, including large-scale climate and ecosystem change, as well as significant management and monitoring changes. We found high coherence in moving window Mohn's rho time series for groundfish within the Gulf of Maine and Georges Bank areas. Fluctuations in Gulf of Maine groundfish Mohn's rho values were most strongly related to lagged bottom temperature and spiny dogfish biomass time series, whereas fluctuations in Georges Bank groundfish Mohn's rho values were strongly related to lagged time series of warm core rings formation from the Gulf Stream. Our identification of coherence in retrospective patterns across groundfish stocks by region supports the idea of common regional drivers with climate and ecosystem changes emerging as the leading contributing factors.

The influence of antibody humanization on shark variable domain (VNAR) binding site ensembles.

Sharks and other cartilaginous fish produce new antigen receptor (IgNAR) antibodies, as key part of their humoral immune response and are the phylogenetically oldest living organisms that possess an immunoglobulin (Ig)-based adaptive immune system. IgNAR antibodies are naturally occurring heavy-chain-only antibodies, that recognize antigens with their single domain variable regions (VNARs). In this study, we structurally and biophysically elucidate the effect of antibody humanization of a previously published spiny dogfish VNAR (parent E06), which binds with high affinity to the human serum albumin (HSA). We analyze different humanization variants together with the parental E06 VNAR and the human Vκ1 light chain germline DPK9 antibody to characterize the influence of point mutations in the framework and the antigen binding site on the specificity of VNARs as reported by Kovalenko etal. We find substantially higher flexibility in the humanized variants, reflected in a broader conformational space and a higher conformational entropy, as well as population shifts of the dominant binding site ensembles in solution. A further variant, in which some mutations are reverted, largely restores the conformational stability and the dominant binding minimum of the parent E06. We also identify differences in surface hydrophobicity between the human Vκ1 light chain germline DPK9 antibody, the parent VNAR E06 and the humanized variants. Additional simulations of VNAR-HSA complexes of the parent E06 VNAR and a humanized variant reveal that the parent VNAR features a substantially stronger network of stabilizing interactions. Thus, we conclude that a structural and dynamic understanding of the VNAR binding site upon humanization is a key aspect in antibody humanization.