Spatial segregation of striped marlin (Kajikia audax) by size in the eastern Pacific Ocean

Striped marlin (Kajikia audax) is an epipelagic fish distributed in oceanic and coastal waters of the Pacific Ocean. This species is usually found in warm and coastal waters with high primary productivity. The main goal of this study was to describe the spatial segregation of striped marlin by average Eye‐Fork length (EFL) in the eastern Pacific Ocean (EPO) and its relationship with environmental variables using EFL data obtained from tuna purse‐seining and Generalized Additive Models (GAMs). The model suggested that larger individuals of striped marlin were more likely to be found in waters with high Chlorophyll‐a concentration (>2 mg/m³) and with temperatures lower than 25°C, within a region known as the “cold tongue” and the Humboldt current system, while smaller individuals were more likely to be found in warmer and low productive areas within a region known as the “warm pool of the EPO.” We observed that set type caused a large variation on average EFL of striped marlin; larger fish were captured in sets associated with floating objects (natural and manmade), while smaller fish were captured in sets associated with dolphins. Despite this, our findings suggest that striped marlin has a latitudinal gradient in average EFL; larger individuals occurred predominantly south of 10°N, while smaller ones occurred predominantly in coastal waters between 10°N and 20°N, thus demonstrating a spatial segregation of the species affected by its maturity stage.     

Thermal habitat of striped bass (Morone saxatilis) in coastal waters of northern Massachusetts,USA, during summer

Striped bass, Morone saxatilis, were captured and released with temperature‐measuring data storage tags in Salem Sound, Massachusetts, to collect data on their thermal preferences in coastal and marine waters and to identify environmental factors that may influence temperatures experienced during their summer residence. Striped bass recaptured during summer of 2006 (21 of 151 releases) experienced a wide range of temperatures (6.5–28.0°C) while at‐large for 1–53 days. Overall mean temperature and standard deviation selected by striped bass recaptured in Salem Sound during the longest commonly‐shared duration of time (3–12 July) were 17.8 and 3.57°C, respectively. Comparison of temperature data between fish and 13 vertical arrays in Salem Sound revealed that striped bass experienced higher and more variable temperatures, and that daily changes in temperature actually experienced were unrelated to daily changes in surrounding ambient temperature. Regular cyclical changes in temperature of all striped bass and vertical arrays were identified as influences of the local tide, which contributed about a 2°C change in temperature, on average, over the complete cycle. Most striped bass appeared to limit their activities to depths shallower than the lower limit of the thermocline, above which temperatures generally exceed 9.0°C in Salem Sound. Therefore, it is likely that the vertical distribution of striped bass is restricted by the low temperatures below this depth. An implication of this finding is that the spatial distribution of striped bass may be defined coarsely by knowledge of the distribution of temperature in coastal areas.     

Movement,depth distribution and survival of spinetail devilrays (Mobula japanica) tagged and released from purse‐seine catches in New Zealand

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Movement and behaviour of large southern bluefin tuna (Thunnus maccoyii) in the Australian region determined using pop‐up satellite archival tags

Pop‐up satellite archival tags (PSATs) were deployed on 52 large (156–200 cm length to caudal fork) southern bluefin tuna (Thunnus maccoyii) in the western Tasman Sea during the austral winters of 2001–2005. Southern bluefin tuna (SBT) were resident in the Tasman Sea for up to 6 months with movements away from the tagging area occurring at highly variable rates. The data indicated a general tendency for SBT to move south from the tagging area in the Western Tasman Sea. Four individuals migrated west along the southern continental margin of Australia and into the Indian Ocean. Three individuals moved east into the central Tasman Sea, with one individual reaching New Zealand. We also describe the first observed migration of an SBT from the Tasman Sea to the Indian Ocean spawning grounds south of Indonesia. Individuals spent most of their time relatively close to the Australian coast, with an estimated 84% of time spent in the Australian Fishing Zone. SBT favored temperatures between 19 and 21°C, adjusting their depth to the vertical temperature distribution. Distinct diurnal diving patterns were observed and adjustment of depth to maintain constant ambient light levels over a 24‐h period. The findings of this study are a significant advance toward greater understanding of the spatial dynamics of large SBT and understanding the connectivity between distant regions of their distribution.     

Vertical movements of bigeye tuna (Thunnus obesus) associated with islands, buoys, and seamounts near the main Hawaiian Islands from archival tagging data

To learn more about the movement patterns of bigeye tuna (Thunnus obesus), we deployed archival tags on 87 fish ranging in fork length from 50 to 154 cm. Thirteen fish were recaptured, from which 11 archival tags were returned, representing in aggregate 943 days‐at‐liberty. We successfully retrieved data from 10 tags, representing 474 days in aggregate. The largest fish recaptured was 44.5 kg [131 cm fork length (FL)] and the smallest 2.8 kg (52 cm). The deepest descent recorded was 817 m, the coldest temperature visited 4.7°C, and minimum oxygen level reached ～1 mL L^?1. Fish spent little time at depths where water temperatures were below 7°C and oxygen levels less than ～2 mL L^?1. Five fish were recaptured near the offshore weather buoy where they were tagged. Based on vertical movement patterns, it appeared that all stayed immediately associated with the buoy for up to 34 days. During this time they remained primarily in the uniform temperature surface layer (i.e. above 100 m). In contrast, fish not associated with a floating object showed the W‐shaped vertical movement patterns during the day characteristic of bigeye tuna (i.e. descending to ～300–500 m and then returning regularly to the surface layer). Four fish were tagged and subsequently recaptured near Cross Seamount up to 76 days later. These fish exhibited vertical movement patterns similar to, but less regular than, those of fish not associated with any structure. Bigeye tuna appear to follow the diel vertical movements of the deep sound scattering layer (SSL) organisms and thus to exploit them effectively as a prey resource. Average night‐time depth was correlated with lunar illumination, a behaviour which mimics movements of the SSL.     

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.     

Movements and behaviors of swordfish Xiphias gladius in the United States Pacific Leatherback Conservation Area

This study reports on the movements of swordfish tagged within the Pacific Leatherback Conservation Area (PLCA), an expansive region (>500,000 km²) off the U.S. West Coast that has been seasonally restricted to drift‐gillnet fishing since 2001 to reduce leatherback sea turtle (Dermochelys coricea) interactions. Thirteen swordfish were outfitted with satellite‐linked archival tags scheduled for short (2–20 days, n = 11) and longer‐term (150 days, n = 2) data collection. All tags were deployed on basking swordfish using traditional harpoon‐based methods during the fall of 2012–2013, near offshore seamounts (35.6°N/122.9°W to 37.4°N/123.5°W). Depth and temperature data from 11 swordfish (~90 to 150 kg) resulted in <251 days of movement information from the PLCA region. All tagged individuals exhibited surface‐oriented nocturnal movements, spending >99% of the night above the average thermocline depth (37.5 m), with an average night depth of 8.3 ± 1.6 m. Daytime depth distribution was greater and more variable (mean 107.1 ± 21.2 m), with fish primarily displaying three behavioral patterns: (i) basking activity, 16.7% of the day, (ii) a mixed‐layer distribution between 3 m and the thermocline (26.8% of the day), and (iii) prolonged dives below the thermocline, 56.5% of the day. For seven of the tracks, daytime basking rates increased when thermocline depth was <37 m. As fish moved offshore, there was less variability in vertical movements with a reduction in both basking activity and mixed layer occupancy, as well as an increase in average daytime depth. These data are discussed with respect to the potential development of alternative fishery options for the PLCA.     

Behavioural ecology at sea of Atlantic salmon (Salmo salar L.) kelts from a Newfoundland (Canada) river

For migratory fishes such as Atlantic salmon, temporal variation in the utilization of thermal and depth habitats in the marine environment is likely to occur at both broad and fine scales, reflecting both ecological and metabolic factors. To test this, we implanted 26 Atlantic salmon kelts (i.e., post‐spawners) descending Campbellton River, Newfoundland, with data storage tags that recorded date/time, internal and external temperatures, pressure, and light. The salmon that returned to Campbellton River after an average of 62 days at sea were consecutive spawning kelt. Detailed data were recovered from eight of these fish and revealed distinct patterns in their utilization of thermal and depth habitats. Water temperatures experienced over the period at sea showed a wide range for all fish (from <0 to nearly 20°C); however, there were two clear frequency modes; one at 6–7°C and the other at 11–12°C. The cooler mode was indicative of daytime profiles and the warmer mode of night‐time profiles. This corresponded with the depth profiles, which indicated that salmon dove more frequently below 5 m (mean ± SD = 23 ± 0.9 dives per day) and spent less time (approximately 18%) near the sea surface (<1 m) during the day than during the night (4 ± 0.4 dives per night; approximately 45% time <1 m). The diurnal pattern may be indicative of a reliance on vision for feeding at depth and the short duration of dives (<10 min) may be a strategy that allows salmon a metabolic advantage (e.g., swimming capacity) over their prey living constantly at depth in cool waters.     

Overwintering dormancy behaviour of the European eel (Anguilla anguilla L.) in a large lake

Overwintering dormancy behaviour was studied in female silver eels in Lake Mälaren in Sweden between 2008 and 2010. Depth choices and movements in relation to temperature were analysed from pressure and temperature records for 13 eels with implanted data storage tags, covering 17 overwintering periods and three intervening summer periods. Dormancy commenced in October–November as temperatures fell below 4–12 °C. Eels tended to remain motionless throughout the winter, with some short periods of activity signalled by small changes in depth distributions. During dormancy, the eel shows a clear avoidance of shallow areas <5 m in favour of the 10–25‐m‐depth interval. Activity tended to resume 4–6 months later in April–May as temperatures rose above 3–7 °C and ice cover broke, and eels spent more time at shallower depths of <5–10 m. The majority of the eels were assessed as being in the silver eel stage at the time of tagging. During the autumn months, the diving behaviour, with frequent and large vertical excursions and periods at the surface, was similar to that seen in migrating eels in the Baltic and Atlantic Ocean. In spring and summer, the behaviour differed, being dominated by more gradual depth variations, implying that the eels reverted from silver eel migration behaviour to yellow eel foraging behaviour. Body weight declined during dormancy, but other studies of starvation over comparable time periods showed significantly higher average specific weight losses, implying that the Mälaren silver eels must have fed between the end of dormancy and recapture.     

Influence of incubation temperature on body movements of Atlantic cod (Gadus morhua L.) embryos and on size at hatch

Body movements of cod (Gadus morhua L.) embryos reared from fertilization to hatch at 5.4°C were observed at various stages of development and at six experimental temperatures ranging from 0–10°C. Frequency of cod embryo body movements increased from zero at 42 degree‐days post fertilization to maximal at 73–82 degree‐days (1 or 2 days prior to hatch). Embryos were most active at 2°C (mean of 5.5 movements per 10 min), with activity declining to less than 1/10 min at 8–10°C. Lengths of hatched cod larvae reared at a series of constant temperatures (from 4–10°C) from fertilization to hatch were greater at lower incubation temperatures. Incubation temperatures of 2–4°C were found to be optimal for incubation of cod eggs.     

Insights into the horizontal movements,migration patterns,and stock affiliation of California swordfish

This study reports on the horizontal movements of swordfish (Xiphias gladius L.) tagged during deep‐set fishery trials off the California coastline. Position estimates from several electronic tag types were used to better understand swordfish stock structure and regional affiliation with current boundary hypotheses used to manage swordfish in the eastern north Pacific. Swordfish were outfitted with (a) satellite‐linked mark–recapture tags (n = 66), (b) electronic data storage tags that were recaptured (n = 16), (c) fin‐mounted Argos transmitters (n = 6), and (d) satellite‐linked archival tags (n = 4). Twenty‐six percent of tagged swordfish reported close to (<225 km) their deployment location within the southern California Bight (SCB). Of the 50 swordfish that moved outside the SCB, 76% exhibited affiliation to the Eastern Pacific Ocean (EPO) management unit, 20% moved into the Western and Central North Pacific (WCNP) and 4% spent time within both the EPO and WCNP boundaries. Mean displacement between deployment and reporting locations was 1,250 ± 1,375 km, with daily rates of movement up to 55 km/day. Seasonal migrations ranged from the equator (0.8°N.132.4°W) to the Hawaiian Islands (17.0°N/154.2°W), with multiple individuals returning to the initial tagging locations the subsequent season. Seasonal site fidelity exhibited by several individuals highlights the importance of the SCB foraging grounds. While no evidence of trans‐equatorial or trans‐Pacific crossing was documented, extensive movements validate the highly migratory nature of California swordfish and support the need for future inclusion of spatial distribution data in management. Findings suggest that SCB swordfish may exhibit a higher level of EPO connectivity than previously proposed.     

Reproductive performance and seasonal plasma sex steroid and metabolite levels in a captive wild broodstock of brill Scophthalmus rhombus L.

This study reports egg production by captive wild brill Scophthalmus rhombus, a potential new flatfish species for Southern Europe‐Mediterranean mariculture, as well as seasonal plasma levels of 17β–estradiol, testosterone, 11–ketotestosterone, proteins, triglycerides, glucose and lactate. A mean egg production of 102 800 eggs kg body weight⁻¹ was achieved during the 2005 spawning period (January–March), although a continuous egg supply could only be obtained from some females, which had a higher relative fecundity (261 019±10 393 eggs kg⁻¹) with 12–17 eggs batches released at a mean interval of 3.4 days. Most eggs were obtained with water temperatures ranging from 12 to 14°C, and under increasing temperatures (up to 2.9°C). Potential egg viability (70.1±2.9%), fertilization (72.2±3.4%) and hatching rates (31.9±3.9%) showed high variability, with potential viability tending to decrease as the water temperature increased (mainly between 16 and 17°C) and 0% hatching above 16.6°C. The endocrine changes that brill underwent during late gametogenesis, spawning and postspawning periods were similar to those reported in other Pleuronectiformes. This study establishes an important basis for further research on the biology and physiology of brill reproduction, directed towards the optimization of the breeding techniques used currently.     

Thermal ecology of subadult and adult muskellunge in a thermally enriched reservoir

The movement of adult muskellunge, Esox masquinongy Mitchill, has been investigated in a variety of systems, but temperature selection by muskellunge has not been examined where well‐oxygenated waters were available over a range of temperatures for much of the year. Thirty subadult and adult muskellunge tagged internally with temperature‐sensing radio tags were tracked from March 2010 to March 2011 in a Tennessee reservoir. Mean tag temperatures were 18.9 °C in spring (March to May), 22.1 °C in summer (June to August), 16.5 °C in autumn and 9.8 °C in winter (December to February). When the greatest range in water temperatures was available (7.1–33.3 °C; May to early August 2010), their realised thermal niche (mean ± 1 SD) was 22.3 °C ± 1.8; the realised thermal niche was affected by fish size (smaller fish selected slightly warmer temperatures) but not sex. An electric generating steam plant discharging warm water resumed operation in January 2011, and most (86%) tagged fish occupied the plume where temperatures were ≈10 °C warmer than ambient water temperatures. No mortalities were observed 15 days later when plant operations ceased. Their affinity for the heated plume prompted concerns that muskellunge will be too easily exploited when the plant operates during winter.     

Effect of temperature on the development, growth, survival and settlement of green mussel Perna viridis (Linnaeus, 1758)

The effect of temperature on the development, growth, survival and settlement of Perna viridis was studied under controlled conditions to provide information needed for the development of commercial hatchery technology for green mussel P. viridis. Total mortality of the larvae occurred after 24 h at temperatures of 33°C and 35°C. At 24°C, larvae took longer to settle than at temperatures of 27°C, 29°C and 31°C. For optimum larval development (8–13 h), growth (17.2±0.84 μm day^–1) and survival (55.2±0.84%), a hatchery rearing temperature of 31°C is required. For settlement no significant difference was seen between the percentage settlement at 29°C (49.3±3.34%) and 31°C (45.8±1.76%). However, the process of settlement began and ended earlier at 29°C (from 15 to 18 days) than at 31°C (from 18 to 20 days). Thus for larval settlement a temperature of 29°C is recommended.     

Effect of high water temperature on the survival, moulting and food consumption of Penaeus (Marsupenaeus) japonicus (Bate, 1888)

The kuruma shrimp, Penaeus (Marsupenaeus) japonicus (Bate, 1888), is a valuable aquaculture species in Queensland, Australia. The shrimp is supplied live to the Japanese market and must survive emersed transport for up to 36 h. In-transit mortality after harvest from high water temperatures (> 30 °C) has been reported by the industry, and a knowledge of the effects of high water temperature may provide important information for producers on grow-out management, timing of production and farm location. Experiments were conducted to determine the effect of high water temperature on survival, moulting and food consumption in P. japonicus. Replicated groups of 15.6 ± 0.2 g shrimp were acclimated and exposed to five temperatures, between 28 and 36 °C, for up to 28 days. Mortality was highest at 36 °C and equally lowest between 28 °C and 32 °C. Intermoult period was not significantly different for temperatures between 28 and 32 °C (19.8–15.5 days) but was significantly greater above 32 °C (27.4 days at 34 °C and > 104 days at 36 °C). There was evidence of moulting synchrony at 28 °C. Mean daily food consumption was highest at 32 °C at 2.34% of body weight, but decreased to 1.56% at 28 °C and 1.33% at 36 °C. Over the range of water temperatures examined, survival, moulting rate and food consumption were highest at 32 °C.     

Lunar landings—Relationship between lunar phase and catch rates for an Australian gamefish-tournament fishery

Catch-per-unit-of-effort (CPUE) data were collected from anglers participating in gamefish tournaments off the coast of New South Wales, Australia, over nine consecutive years (1994–2003). Mean catch rates for 381 tournament days were aggregated by “lunar phase day” in order to analyse relationships between CPUE and lunar phase for eight primary gamefish species. Circular–linear correlation analysis identified significant relationships between moon phase and CPUE for black marlin (Makaira indica), blue shark (Prionace glauca), shortfin mako shark (Isurus oxyrinchus), dolphin fish (Coryphaena hippurus), and yellowfin tuna (Thunnus albacares) while no significant relationship was evident for blue marlin (Makaira mazara), striped marlin (Tetrapterus audax) and tiger shark (Galeocerdo cuvier). Periodic regression was used to identify the nature of the relationship between lunar phases and catch rates for these species. A consistent pattern of catch rates peaking over the period from the new moon to the first quarter was observed for blue shark, mako shark, dolphin fish and yellowfin tuna. Results for black marlin differed, with catch rates increasing to a peak between the full moon and the last quarter. We suggest that the observed variability in CPUE maybe a result of the movement of prey species in association with lunar phase. Further, we hypothesise that the observed species-specific differences in CPUE of gamefish are primarily mediated by physiological adaptations and limitations, which directly affect the ability of these predators to maintain access to their prey.     

Factors influencing the at-haulback mortality of striped marlin Tetrapturus audax caught by tuna longline fishery in the western Indian Ocean

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The marine temperature and depth preferences of Arctic charr (Salvelinus alpinus) and sea trout (Salmo trutta), as recorded by data storage tags

Eleven Arctic charr (Salvelinus alpinus) (370–512 mm) and eight sea trout (Salmo trutta) (370–585 mm in length) were tagged externally or internally with depth‐ and temperature‐measuring data‐storage tags (DST) before they were released into the sea in the Alta Fjord in north Norway in June 2002. All sea trout were recaptured after they spent 1–40 days at sea, while all Arctic charr were recaptured after 0.5–33 days at sea. On average, trout preferred water about 0.6 m deeper and 1.3°C warmer than Arctic charr. Arctic charr spent >50% of their time between 0 and 1 m depth, while trout spent >50% of their time between 1 and 2 m depth. Both species spent >90% of their time in water no deeper than 3 m from the water surface. However, sea trout dove more frequently and to greater depths (max. 28 m) than Arctic charr (max. 16 m), and these deep dives were most frequently performed at the end of the sea migration. Arctic charr demonstrated a diel diving pattern, staying on average about 0.5 m deeper between 08:00 hours and about 15:00 hours than during the rest of the 24 h, even though there was continuous daylight during the experiments. When comparing data obtained from the DSTs with temperature measurements within the fjord system, the two species were observed to select different feeding areas during their sea migration, the sea trout choosing the inner and warmer parts of the fjord, in contrast to the Arctic charr that preferred the outer, colder parts of the fjord. The observed differences in migration behaviour between the two species are discussed in relation to species preferences for prey and habitat selection, and their optimal temperatures for growth.     

Migration and behavior of juvenile North Pacific albacore (Thunnus alalunga)

Archival tags were used to study the seasonal movements, migration patterns and vertical distribution of juvenile North Pacific albacore (Thunnus alalunga). Between 2001 and 2006, archival tags were deployed in North Pacific albacore in two regions of the Northeast Pacific: (i) off Northern Baja California, Mexico and Southern California, and (ii) off Washington and Oregon. Twenty archival tagged fish were recovered with times at liberty ranging from 63 to 697 days. Tagged albacore exhibited five distinct, seasonal migratory patterns. Depth and temperature data also showed a broad range of vertical behaviors. In certain regions such as off Baja California, Mexico, juvenile albacore make frequent dives to depths exceeding 200 m during the day and remain in the surface mixed layer at night, whereas off Oregon and Washington they remain near the surface both day and night. Water temperatures encountered ranged from 3.3 to 22.7°C. Peritoneal temperatures were significantly higher by an average of approximately 4°C, as expected in these warm‐bodied fish. This study provides a comprehensive examination of horizontal and vertical movements of juvenile albacore in the Northeast Pacific. The results reveal diverse behavior that varies regionally and seasonally as albacore move among different habitats throughout the entire North Pacific.     

Effects of salinity and temperature during incubation on hatching and development of lingcod Ophiodon elongatus Girard, embryos

The interactive effects of salinity and temperature on development and hatching success of lingcod, Ophiodon elongatus Girard, were studied by incubating eggs at four temperatures (6, 9, 12 and 15°C) and five salinities (15, 20, 25, 30 and 35 g L^?1). Hatch did not occur in any of the 15°C treatments. Degree days (°C days) to first hatch was not influenced by temperature or salinity, however, calendar days to first hatch differed significantly for temperature (P<0.0001, 61±1, 44±1 and 35±1 days for 6, 9 and 12°C respectively). Degree days to 50% (427.1±4.2) hatch was not significantly influenced by temperature but was by salinity (P=0.0324). Viable hatch (live with no deformities, 74.1±4.0%) was greatest at 9°C and 25 g L^?1 but not significantly different in the range of 20–30 g L^?1. Larval length (9.4±0.13 mm) was greatest at 9°C and 20–30 g L^?1. Temperature and salinity significantly influenced all categories of deformities with treatments at the upper (12°C and 35 g L^?1) and lower limits (6°C and 15 g L^?1) producing the greatest deformities. The optimal temperature and salinity for incubating Puget Sound lingcod eggs was found to be 9°C and 20–30 g L^?1.