The development of the northern European fishery for north Atlantic bluefin tuna Thunnus thynnus during 1900–1950

North Atlantic bluefin tuna, Thunnus thynnus, used to migrate to northern European waters (Norwegian Sea, North Sea, Skagerrak, Kattegat, and Øresund) where it supported important commercial and sportfisheries. The species disappeared from the region in the early 1960s and the species is now still extremely rare. The factors which led to the development of the fishery and its subsequent decline remain unclear and poorly documented. This investigation documents the development of the fishery in terms of landings, effort, and gears with focus on the time period from 1900 to 1950 when landings were increasing. The species was frequently sighted while fishermen were targeting other species (herring, mackerel) and occasionally was caught as bycatch with these and other species. Information from scientifically trained observers demonstrate that tuna schools were common in the North Sea for 2–3 months during the summers of 1923–1931. As fishermen realized that the species had market value, new catch methods were developed and employed. These included harpoon-rifle, improved hook and line methods, and hydraulically operated purse seines. Landings rose sharply as did the number of vessels and the capacity of processing facilities for bluefin tuna. Bluefin tuna in this area were generally medium-large (>50 kg whole weight). The most important countries which participated in bluefin tuna fisheries in this period were Norway, Denmark and Sweden, but bluefin tuna were also exploited by France, Germany, The Netherlands and the United Kingdom. Similarly sportfishing increased in popularity in some of these countries and attracted many foreign participants. The increase in landings between 1900 and 1950 was driven particularly by an increase in fishing effort and technology. We found no evidence that the increase was due to a temperature-related shift in habitat into the region. Our results demonstrate that the species was an important part of the ecosystem at least back to the early 1900s and that commercial and recreational fisheries were well established in northern European waters before official ICCAT records.     

中华鳖dazl基因克隆及在生殖细胞中的表达

为探索龟鳖类生殖细胞的发育分化机制,实验通过特异性引物克隆了中华鳖dazl基因的cDNA片段,长1 007 bp,其中包括5′端非编码区197 bp,3′端非编码区33 bp,开放阅读框777 bp,编码258个氨基酸。氨基酸序列比对显示其与西部锦龟Dazl同源性最高,达96%;与小鼠Dazl同源性达75%。荧光定量PCR分析结果显示,中华鳖dazl mRNA主要在精巢和卵巢中表达,在体细胞组织中仅检测到微量表达。冰冻切片原位杂交结果显示,中华鳖dazl mRNA在生殖细胞中特异表达,且在不同时期的生殖细胞中呈动态表达模式。在精巢中,中华鳖dazl mRNA在初级和次级精母细胞中表达最强,在精原干细胞中表达水平次之,在精子细胞中未检测到信号;在卵巢中,中华鳖dazl mRNA信号在初级卵母细胞胞质中均匀分布且在最早期的初级卵母细胞中信号最强,随着卵母细胞的增大,信号逐渐聚集并逐渐减弱。研究表明,dazl基因可能对中华鳖两性生殖细胞的发生具有重要的调控作用。     

Retinal ganglion cell topography in juvenile Pacific bluefin tuna Thunnus orientalis (Temminck and Schlegel)

The retinal ganglion cell distribution, which is known to reflect fish feeding behavior, was investigated in juvenile Pacific bluefin tuna Thunnus orientalis. During the course of examination, regularly arrayed cells with a distinctive larger soma, which may be regarded as motion-sensitive cells, were found. The topographical distribution of ordinary-sized ganglion cells, which is usually utilized to estimate fish visual axis and/or visual field characteristics, showed that the highest-density area, termed the area centralis, was localized in the ventral-temporal retina. The retinal topography of ordinary-sized ganglion cells seems to reflect the bluefin tuna’s foraging behavior; while cruising, cells in the area centralis may signal potential prey, such as small schooling pelagic fishes or squids, that are present in the upward-forward direction. Judging from morphological characteristics, the large ganglion cells localized in the small temporal retinal area seem to be equivalent to physiologically categorized off-center Y-cells of cat, which are stimulated by a transient dark spot in a bright visual field. It was inferred that presumed large off-center cells in the temporal retina detect movements of agile prey animals escaping from bluefin tuna as a silhouette against environmental light.     

Molecular evidence for cosmopolitan distribution of platyhelminth parasites of tunas (Thunnus spp.)

Global distribution of platyhelminth parasites and their host specificities are not well known. Our hypothesis was that platyhelminth parasites of large pelagic fishes are common around the world. We analysed molecular variation in three different taxa of platyhelminth parasites infecting four species of tunas: yellowfin tuna (Thunnus albacares, Scombridae) from Western Australia, southern bluefin tuna (Thunnus maccoyii, Scombridae) from South Australia, Pacific bluefin tuna (Thunnus orientalis, Scombridae) from Pacific Mexico and northern bluefin tuna (T. thynnus, Scombridae) from two localities in the Mediterranean (Spain and Croatia). Comparisons of ITS2 and partial 28S rDNA demonstrated two congeneric species of blood flukes (Digenea: Sanguinicolidae) from multiple hosts and localities: Cardicola forsteri from southern bluefin and northern bluefin tunas, and Cardicola sp. from Pacific bluefin and northern bluefin tunas; and a gill fluke, Hexostoma thynni (Polyopisthocotylea: Hexostomatidae), from yellowfin, southern bluefin and northern bluefin tunas. Partial 28S rDNA indicates that a second type of fluke on the gills, Capsala sp. (Monopisthocotylea: Capsalidae), occurs on both southern bluefin and Pacific bluefin tunas. This appears to be the first report of conspecific platyhelminth parasites of teleosts with a wide‐ranging geographical distribution that has been confirmed through molecular approaches. Given the brevity of the free‐living larval stage of both taxa of flukes on the gills (H. thynni and Capsala sp.), we conclude that the only feasible hypothesis for the cosmopolitan distribution of these flatworms is migrations of host tunas. Host migration also seems likely to be responsible for the widespread occurrence of the two species of blood flukes (Cardicola spp.), although it is also possible that these were translocated recently by the spread of infected intermediate hosts.     

Environmental influences on Atlantic bluefin tuna (Thunnus thynnus) catch per unit effort in the southern Gulf of St. Lawrence

The Atlantic bluefin tuna (Thunnus thynnus) population in the western Atlantic supports substantial commercial and recreational fisheries. Despite quota establishment and management under the auspices of the International Commission for the Conservation of Atlantic Tunas, only small increases in population growth have been estimated. In contrast to other western bluefin tuna fisheries indices, contemporary estimates of catch per unit effort (CPUE) in the southern Gulf of St. Lawrence have increased rapidly and are at record highs. This area is characterized by the Cold Intermediate Layer (CIL) that is defined by waters <3°C and located at depths of 30–40 m in September. We investigated the influence of several in situ environmental variables on the bluefin tuna fishery CPUE using delta‐lognormal modelling and relatively extensive and consistent oceanographic survey data, as well as dockside monitoring and mandatory logbook data associated with the fishery. Although there is considerable spatial and temporal variation of water mass characteristics, the amount of available habitat in the southern Gulf of St. Lawrence (assuming a > 3°C thermal ambit) for bluefin tuna has been increasing. The percentage of the water column occupied by the CIL was a significant environmental variable in the standardization of CPUE estimates. There was also a negative relationship between the spatial extents of the CIL and the fishery. Properties of the CIL account for variation in the bluefin tuna CPUE and may be a factor in determining the amount of available feeding habitat for bluefin tuna in the southern Gulf of St. Lawrence.     

Cell-cell interactions in the testis of the dogfish: stage-related changes in protein synthesis

Previous studies have shown that the testis of Selachians is a very suited model to study stage-dependent changes in Sertoli cells during spermatogenesis (Dubois and Callard 1989; Sourdaine et al. 1990). In the dogfish testis (here: Scyliorhinus canicula), germ cells, at an identical stage of spermatogenesis, are associated with Sertoli cells to form spermatocysts, which are arranged in zones corresponding to the different stages of spermatogenesis. Using previously described methods for the isolation and culture of spermatocysts from four spermatogenic stages (spermatogonia, spermatocytes, early spermatids and late spermatids; Sourdaine and Jégou 1989; Sourdaine and Garnier 1992) and electrophoresis techniques (1D and 2D-SDS-PAGE) we have investigated the [³⁵S] methionine incorporation into proteins in the dogfish testis. Our results indicate that protein synthesis reaches a maximum in spermatocysts with spermatocytes. Marked stage-related changes of protein synthesis and secretion were also observed on the autoradiograms of 1D and 2D-SDS-PAGE. Further investigations of the paracrine control of germ cells on Sertoli cell protein synthesis requires the identification of specific Sertoli cell proteins in the dogfish.     

Metazoan parasites on gills of Southern Bluefin Tuna (Thunnus maccoyii) do not rapidly proliferate after transfer to sea cages

A relatively new and highly valuable aquaculture industry focuses on three species of bluefin tunas, which are captured from the wild and fattened for several months in sea cages. In teleost aquaculture, mortalities and extra production costs are very commonly associated with metazoan ectoparasites. In tuna, however, the production value lost due to diseases associated with ectoparasites is unknown. We collected epidemiological data on burdens of metazoans on the gills of farmed southern bluefin, Thunnus maccoyii, in a series of monthly samples of tuna from the time of stocking through to harvest (March to August, 2004; N = 210) in five sea cages on a farm off Port Lincoln, Australia. Three species were recorded; for one (a copepod, Pseudocycnus appendiculatus), there was a gradual, significant increase in both abundance (from a mean of 0.1 in March, to 3.83 in August) and prevalence (from 10% to 67.5%). For the other two species (a second copepod, Euryphorus brachypterus, and a polyopisthocotylean flatworm, Hexostoma thynni) there were no discernible trends in prevalences and abundances. These results contrast markedly with those of other intensively cultured species of finfishes, in which parasite epizootics are frequent. This finding may indicate that despite the stresses of captivity, tuna mount a robust immune response to ectoparasites; the relatively low stocking densities at which tuna are farmed may facilitate this. The fall in water temperature during farming (22 °C to 13 °C) may also reduce the reproductive rate of these ectoparasites.     

Bluefin tuna (Thunnus thynnus) distribution in relation to sea surface temperature fronts in the Gulf of Maine (1994–96)

Fishery‐linked aerial surveys for bluefin tuna (Thunnus thynnus) were conducted in the Gulf of Maine (GOM) from July through October, 1994–96. Each year, from 507 to 890 surface schools were detected and their locations examined in relation to oceanographic conditions. Correlations between bluefin tuna presence and environmental variables were explored for sea surface temperature (SST), distance to a SST front, frontal density (relative density of all SST fronts seen in a given 1 km area for 2 weeks prior to each tuna sighting), and bottom depth and slope. Mean SST associated with bluefin schools was 18.1°C (±2.8). Schools were located at a mean distance of 19.7 km (±19.6) from SST fronts, and in water masses with an average frontal density of 28.2 m km^?2 (±35.7). Mean bottom depth of detected schools was 139.0 m (±70.3), and mean bottom slope was 0.7% rise (±0.7). A binomial generalized linear model fit to these variables indicated that bluefin are seen closer to fronts than locations in which no tuna were seen. Using simple and partial Mantel tests, we investigated the spatial correlation between bluefin tuna presence and the environmental variables, controlling for spatial autocorrelation. For each day that schools were sighted, we performed 24 Mantel tests, on a combination of response and predictor variables. The spatial relationship between bluefin tuna and SST fronts was inconsistent. Our analysis identified significant spatial structure in the bluefin school locations that had no significant correlation with any of the measured environmental features, suggesting that other untested features, such as prey density, may be important predictors of bluefin distribution in the GOM.     

Genotyping‐by‐sequencing for construction of a new genetic linkage map and QTL analysis of growth‐related traits in Pacific bluefin tuna

Pacific bluefin tuna (Thunnus orientalis) has high market value, but its wild populations have decreased in recent years. The broodstock of Pacific bluefin tuna that were hatched artificially and reared under aquaculture conditions is beginning to be used for production. The creation of broodstock with commercially valuable traits, such as rapid growth, is therefore of great interest. Genetic linkage map‐based identification of markers associated with quantitative trait loci (QTLs) facilitates marker‐assisted selection (MAS) breeding and allows efficient genetic improvement of broodstock. Single nucleotide polymorphism (SNP)‐based genetic linkage map construction using the genotyping‐by‐sequencing method can expand the number of mapped markers and help identify growth‐related QTLs. In this study, we constructed sex‐specific maps for 24 linkage groups consisting of 677 SNP and 651 microsatellite markers. The total lengths of 93 progenies in the mapping population followed normal distribution, with an average length of 9.4 mm. We performed composite interval mapping in the mapping population. QTL analysis revealed one significant QTL in LG10 on the female linkage map. The genetic linkage map—the second such map generated for Pacific bluefin tuna—and the growth‐related QTLs detected in this study will be useful for tuna aquaculture MAS programs.     

Decadal variation in the trans-Pacific migration of northern bluefin tuna (Thunnus thynnus) coherent with climate-induced change in prey abundance

Northern bluefin tuna, Thunnus thynnus, apparently spawn only in the western Pacific and a portion of the juveniles migrate to the eastern Pacific. During the past decade, catches of northern bluefin in the eastern Pacific have declined. One possible cause for this decline, proposed by bluefin stock assessment studies, is a decline in the proportion of bluefin that migrate out of the western Pacific. This hypothesis is examined with several indices of the relative abundance of bluefin tuna in the western and eastern Pacific. These indices suggest a decline in the proportion of bluefin migrating to the eastern Pacific since 1977. This period of reduced bluefin migration coincides with a period when a prey of bluefin, Japanese sardine, Sardinops melanosticta, were abundant off Japan. It is hypothesized that in years when sardines are abundant off Japan, a higher proportion of bluefin stay in the western Pacific compared with years when sardines are scarce. Currently, the adun-dance of sardines off Japan is declining. If this decline continues, this hypothesis predicts an increase in bluefin migrating north of Hawaii and into the eastern Pacific.     

Molecular characterization of southern bluefin tuna myoglobin (<Emphasis Type="Italic">Thunnus maccoyii</Emphasis>)

The primary structure of southern bluefin tuna Thunnus maccoyii Mb has been elucidated by molecular cloning techniques. The cDNA of this tuna encoding Mb contained 776 nucleotides, with an open reading frame of 444 nucleotides encoding 147 amino acids. The nucleotide sequence of the coding region was identical to those of other bluefin tunas (T. thynnus and T. orientalis), thus giving the same amino acid sequences. Based on the deduced amino acid sequence, bioinformatic analysis was performed including phylogenic tree, hydropathy plot and homology modeling. In order to investigate the autoxidation profiles, the isolation of Mb was performed from the dark muscle. The water soluble fraction was subjected to ammonium sulfate fractionation (60–90 % saturation) followed by preparative gel electrophoresis. Autoxidation profiles of Mb were delineated at pH 5.6, 6.5 and 7.4 at temperature 37 °C. The autoxidation rate of tuna Mb was slightly higher than that of horse Mb at all pH examined. These results revealed that tuna myoglobin was unstable than that of horse Mb mainly at acidic pH.     

Inclusion of prey data improves prediction of bluefin tuna (Thunnus thynnus) distribution

We examined the distribution of Atlantic bluefin tuna ( Thunnus thynnus ) in the Gulf of Maine, Northwest Atlantic Ocean, from 17 to 23 August 1995, in relation to physical and biological parameters. Specifically, we fit a binomial GLM to the bluefin tuna presence–absence data and predictor variables that include: sea surface temperature (SST), ocean depth, distance to an SST front, time-lagged density of SST fronts, and an interpolated surface of Atlantic herring ( Clupea harengus ) density. In addition, we use simple and partial Mantel tests to examine whether bluefin tuna presence–absence data are significantly associated with these predictors, once spatial autocorrelation is accounted for. Results suggest that the distribution of bluefin tuna significantly correlated with herring density ( z  =   3.525, P  =   0.000424), and that inclusion of biological variables results in a more parsimonious model. Mantel tests results indicate that bluefin tuna abundance is significantly correlated with herring density after the effect of spatial structure is removed (Mantel r  =   0.043, P  <   0.019).     

Effects of open- and closed-system temperature changes on blood O2-binding characteristics of Atlantic bluefin tuna (Thunnus thynnus)

We investigated the effects of open- and closed-system temperature changes on the O₂ affinity of Atlantic bluefin tuna (Thunnus thynnus) blood using in vitro methods essentially identical to those previously employed on tropical tuna species. Bluefin tuna blood has a general O₂ affinity (P ₅₀ = 2.6–3.1 kPa or 19–23 mm Hg at 0.5% CO₂) similar to that of skipjack tuna, yellowfin tuna, and kawakawa blood (P ₅₀ = 2.8–3.1 kPa at 0.5% CO₂) but significantly above that of bigeye tuna blood (P ₅₀ = 1.6–2.0 kPa at 0.5% CO₂). We therefore hypothesize that bluefin tuna are less tolerant of hypoxia than bigeye tuna. Further, we found the P ₅₀ of bluefin tuna blood to be slightly reduced by a 10°C open-system temperature increase (e.g., from 4.83 kPa at 15°C to 3.95 kPa at 25°C) and to be completely unaffected by a 10°C closed-system temperature change. Bluefin tuna blood, therefore, had a significantly reduced Bohr effect when subjected to the inevitable changes in P CO ₂ and plasma pH that accompany closed-system temperature shifts (0.04–0.09 Δlog P₅₀ΔpH⁻¹) compared with the effects of changes in plasma pH accomplished by changing P CO ₂ alone (0.81–0.94 Δlog P₅₀ Δ pH⁻¹). This response is similar to that of skipjack tuna blood, but different from yellowfin or bigeye tuna blood. During closed-system temperature changes at oxygen levels above P ₅₀, however, bluefin tuna blood showed a reversed temperature effect (i.e., P O ₂ decreased in response to an increase in temperature). Unlike in other tuna species, temperature effects on O₂ affinity of bluefin tuna whole blood were similar to those previously reported for hemoglobin solutions, suggesting that red cell-mediated ligand changes are not involved.     

黑脊倒刺鲃vasa同源基因的克隆及表达分析

为了从分子水平上研究鱼类生殖细胞发育的机制,首次从重要的经济养殖鱼类——黑脊倒刺鲃中克隆了斑马鱼vasa的同源基因ScVHG。该cDNA长1962bp,编码654个氨基酸,氨基酸序列中含有DEAD蛋白家族特有的9个保守结构域。经比对发现,其编码的蛋白序列与斑马鱼VASA蛋白等具有高度的同源性,与斑马鱼、罗非鱼、虹鳟、银鲫、黄鳝、金鱼、金枪鱼、草鱼的VASA蛋白相似度分别为77%,77%,79%,90%,74%,89%,79%和86%。RT-PCR结果显示:在成鱼不同的组织中,ScVHG仅在精巢和卵巢中表达。RNA原位杂交结果进一步表明:在精子发生中,ScVHG只在精原细胞中表达,而在后期的精母细胞、精子细胞中均未发现明显的表达;在卵子发生中,ScVHG在卵原细胞和卵母细胞的各个时相中均有表达,在卵原细胞中表达最为强烈,而在随后各时相的卵母细胞中,阳性信号逐渐减弱。研究认为,该基因中含有的保守序列、序列的相似性以及该基因在生殖细胞中的特异性表达等结果均表明,克隆得到的ScVHG是斑马鱼vasa的同源基因,此基因可作为一种有效的分子标记,用于黑脊倒刺鲃以及其他鱼类生殖细胞发育机制的研究。     

Characterization and ontogenetic development of digestive enzymes in Pacific bluefin tuna Thunnus orientalis larvae

The major digestive enzymes in Pacific bluefin tuna Thunnus orientalis larvae were characterized, and the physiological characteristics of the enzymes during early ontogeny were clarified using biochemical and molecular approaches. The maximum activity of trypsin (Try), chymotrypsin (Ct) and amylase (Amy) was observed at pH 6–11, 8–11 and 6–9, respectively. Maximum activity of Try, Ct and Amy occurred at 50 °C, that of lipase (Lip) was at 60 °C and that of pepsin (Pep) was at 40–50 °C. These pH and thermal profiles were similar to those for other fish species but differed from those previously reported for adult bluefin tuna. Enzyme activity for all enzymes assayed was found to decrease at high temperatures (Try, Ct, Amy and Pep: 50 °C; Lip: 40 °C), which is similar to findings for other fish species with one marked exception—increased Try activity was observed at 40 °C. Lip activity appeared to be dependent on bile salts under our assay conditions, resulting in a significant increase in activity in the presence of bile salts. Ontogenetic changes in pancreatic digestive enzymes showed similar gene expression patterns to those of other fish species, whereas marked temporal increases in enzyme activities were observed at 10–12 days post hatching (dph), coinciding with previously reported timing of the development of the pyloric caeca in bluefin tuna larvae. However, complete development of digestive function was indicated by the high pep gene expression from 19 dph, which contradicts the profile of Pep activity and previously reported development timing of the gastric gland. These findings contribute to the general knowledge of bluefin tuna larval digestive system development.     

Predicting the occurrence of Atlantic bluefin tuna (Thunnus thynnus) larvae in the northern Gulf of Mexico: building a classification model from archival data

Although bluefin tuna are found throughout the Atlantic Ocean, spawning in the western Atlantic has been recorded predominantly in the Gulf of Mexico (GOM) in spring. Larval bluefin tuna abundances from the northern GOM are formulated into an index used to tune the adult stock assessment, and the variability of this index is currently high. This study investigated whether some of the variability in larval bluefin tuna abundances was related to environmental conditions, by defining associations between larval bluefin tuna catch locations, and a suite of environmental variables. We hypothesized that certain habitat types, as defined by environmental variables, would be more likely to contain bluefin tuna larvae. Favorable habitat for bluefin tuna larvae was defined using a classification tree approach. Habitat within the Loop Current was generally less favorable, as were warm‐core rings, and cooler waters on the continental shelf. The location and size of favorable habitat was highly variable among years, which was reflected in the locations of larval bluefin tuna catches. The model successfully placed bluefin tuna larvae in favorable habitat with nearly 90% accuracy, but many negative stations were also located within theoretically favorable habitat. The probability of collecting larval bluefin tuna in favorable habitat was nearly twice the probability of collecting bluefin tuna larvae across all habitats (35.5 versus 21.0%). This model is a useful addition to knowledge of larval bluefin tuna distributions; however, the incorporation of variables describing finer‐scale features, such as thermal fronts, may significantly improve the model’s predictive power.     

Morphological features and functions of bluefin tuna change with growth

Morphological features of Pacific bluefin tuna Thunnus orientalis have important functions for its fast swimming. Morphological features of tuna change with growth; therefore, morphological functions may develop during this process. In this study, we precisely quantified the morphology of bluefin tuna with growth from juvenile to young adult using a three-dimensional laser profiler and evaluated the fluid dynamic characteristics of tuna using computational fluid dynamics (CFD) and an accurate model based on measured data. As results of measurement of morphological features, the aspect ratio and sweepback angle, which are indices of hydrodynamic characteristics for a hydrofoil, suggested that the lift force of caudal fin was increased as the tuna grows. The results of CFD analysis showed that the coefficient of drag force gradually decreased with growth. Pectoral fins generated lift force, and the ratio of lift force to submerged weight (FL/SW) increased as the tuna grew to 0.2 m total length (TL). After the tuna exceeded 0.2 m TL, FL/SW changed to a wider range in angle of attack as the tuna grew. These results suggest that the morphological function of bluefin tuna develops to enhance its swimming ability as it grows from juvenile to young adult.     

Tuna and swordfish catch in the U.S. northwest Atlantic longline fishery in relation to mesoscale eddies

To analyze the effects of mesoscale eddies, sea surface temperature (SST), and gear configuration on the catch of Atlantic bluefin (Thunnus thynnus), yellowfin (Thunnus albacares), and bigeye tuna (Thunnus obesus) and swordfish (Xiphias gladius) in the U.S. northwest Atlantic longline fishery, we constructed multivariate statistical models relating these variables to the catch of the four species in 62 121 longline hauls made between 1993 and 2005. During the same 13‐year period, 103 anticyclonic eddies and 269 cyclonic eddies were detected by our algorithm in the region 30–55°N, 30–80°W. Our results show that tuna and swordfish catches were associated with different eddy structures. Bluefin tuna catch was highest in anticyclonic eddies whereas yellowfin and bigeye tuna catches were highest in cyclonic eddies. Swordfish catch was found preferentially in regions outside of eddies. Our study confirms that the common practice of targeting tuna with day sets and swordfish with night sets is effective. In addition, bluefin tuna and swordfish catches responded to most of the variables we tested in the opposite directions. Bluefin tuna catch was negatively correlated with longitude and the number of light sticks used whereas swordfish catch was positively correlated with these two variables. We argue that overfishing of bluefin tuna can be alleviated and that swordfish can be targeted more efficiently by avoiding fishing in anticyclonic eddies and in near‐shore waters and using more light sticks and fishing at night in our study area, although further studies are needed to propose a solid oceanography‐based management plan for catch selection.