Pacific Halibut Research Articles

Influence of illumination and temperature upon flatfish reactivity and herding behavior: Potential implications for trawl capture efficiency

For both survey and commercial trawls, selection of flatfish species and sizes is strongly influenced by fish behavioral reactions to the ground-gear. Herding begins with initial disturbance, where flatfish are flushed from the sediment by ground-gear. Yet this initial behavioral reaction is poorly understood, especially relative to effects of environmental parameters such as light and temperature. The goal of this study was to examine disturbance and herding behavior in English sole, northern rock sole and Pacific halibut using a simulated trawl footrope, in both light and darkness at 9 °C, and additionally, for rock sole, at 2 °C. In the light, all species exhibited a disturbance response consistent with the initiation of herding; directed swimming in close proximity to the substrate. This response was diminished in darkness, with fish hopping or slowly rising off the bottom, such that the footrope quickly passed beneath them (precluding herding). Low temperature also influenced rock sole behavior, increasing the likelihood that fish would simply hop off the bottom, rather than initiate herding. These results help lay a behavioral framework for understanding such phenomenon as diel and seasonal variations in flatfish catches and fish size composition, and why diel patterns for survey and commercial trawls often differ. Further, difference in behavior between rock sole and Pacific halibut suggest possible avenues of reducing halibut bycatch at night.

Chemical Characterization of Liver Lipid and Protein from Cold‐Water Fish Species

ABSTRACT: The largest US harvests of marine fish for human consumption are from Alaska waters. Livers from these fish are combined with other fish offal and made into fish meal and oil or discarded. The purpose of this study was to characterize liver lipids and proteins from important commercial species including walleye pollock (WP), pink salmon (PS), Pacific halibut (PH), flat head sole (FS), and spiny head rock fish (RF), and underutilized species including arrow tooth flounder (AF) and big mouth sculpin (BS). Liver lipid content ranged from 50.3% in WP to 3.3% in PS. Protein content ranged from 7.7% in WP to 18.4% in BS. PS livers had the highest content of ω‐3 fatty acids at 336 mg/g of oil and AF had the lowest content at 110 mg/g of oil. There were significant differences in the content of 9 amino acids with methionine and lysine values ranging from 2.66% to 3.43% and 7.19% to 9.45% of the total amino acids, respectively. Protein from the cold water marine fish livers was of high quality and the oils contained substantial quantities of ω‐3 fatty acids. Fish livers had distinct chemical properties and can be used for the development of unique food ingredients.

Fisheries management with stock growth uncertainty and costly capital adjustment

We develop a dynamic model of a fishery which simultaneously incorporates random stock growth and costly capital adjustment. Numerical techniques are used to solve for the resource-rent-maximizing harvest and capital investment policies. Capital rigidities bring diminishing marginal returns to the current period harvest, and introduce an incentive to smooth the catch over time. With density-dependent stock growth, however, catch smoothing increases stock variability resulting in reduced average yields. The optimal management policy balances the catch smoothing benefits against yield loss. We calibrate the model to the Alaskan pacific halibut fishery to demonstrate the main insights.

A General Model for Analyzing Data from Mark-recapture Experiments with an Application to the Pacific Halibut

A general model is developed to examine the patterns of the regional movement of tagged and released fish from mark-recapture experiments. It is a stochastic model that incorporates fishing mortality, natural mortality, fish movement, tag-shedding, and different rates of reporting. A likelihood function is constructed for estimating its parameters. We used this model to analyze data on the Pacific halibut from mark-recapture experiments conducted by the International Pacific Halibut Commission (IPHC), with a total of 36,058 releases from 1982 to 1986 and 5,826 recoveries from 1982 to 2000. We estimated their rates of movement among IPHC management areas, along with their instantaneous rates of natural and fishing mortalities. Our analysis revealed that fish movement was not significant among areas, with a resident probability of > 0.92. This lends support to the IPHC catch-at-age stock assessment model (which has no built-in movement components). The estimated instantaneous rate of natural mortality (0.198 year−1) lies between that assumed in all IPHC stock assessments before 1998 (0.20 year−1) and that from 1999 onwards (0.15 year−1). The estimates of the instantaneous rates of fishing mortality were consistent with those from the IPHC stock assessment model.

Risk sensitivity in three juvenile (Age-0) flatfish species: Does estuarine dependence promote risk-prone behavior?

Pleuronectid flatfish are generally thought to use stereotypical anti-predator behavior to reduce encounters with potential predators, including burial, maintaining a low profile on the bottom, cryptic coloration, and reduced activity. However, a series of laboratory experiments demonstrate significantly different predation rates on juvenile (Age-0) English sole ( Parophrys vetulus), northern rock sole ( Lepidopsetta polyxystra), and Pacific halibut ( Hippoglossus stenolepis) by Age-2 Pacific halibut predators, suggesting differing anti-predator strategies and/or capabilities among species. In this study, behavioral attributes that control how conspicuous juvenile flatfish are to their predators, such as burial, body posture, and activity levels, were examined both in the presence and absence of perceived predation risk. English sole exhibited risk-prone behavior; they tended to bury less, exhibit an arched body posture (with head elevated off the bottom), and were more active in both the absence and presence of predators when compared to the other two species. Conversely, rock sole exhibited risk-averse behavior, being buried, inactive, with a flat body posture regardless of predation risk. Halibut demonstrated risk-sensitive behavior; behaving like English sole in the absence of predation risk, and shifted to behavior similar to that of rock sole in the face of predation risk. As an estuarine dependent species, English sole recruit to an environment that tends to be highly turbid reducing encounters with predators. As a result English sole, may have “relaxed” anti-predator behaviors in comparison to northern rock sole and Pacific halibut which recruit to less turbid coastal nurseries.

Neural network and fuzzy logic models for pacific halibut recruitment analysis

Time series based neural network and fuzzy logic models were developed for fish recruitment analysis using fish stock–recruitment data incorporating environmental information. Data from the Pacific halibut stock with the Pacific Decadal Oscillation (PDO) index as the environmental variable was used for the model development. The neural network model was developed based on the multi-layer feed-forward neural network model with back-propagation learning algorithm. The fuzzy logic model was developed based on the fuzzification of the PDO index into two fuzzy sets denoted as “positive” and “negative” regimes. We compared the performance of these models to the traditional Ricker stock–recruitment model and the Ricker model with PDO as covariate. All four models showed significant residual time series structure in the form of first order autocorrelation. To account for this time series structure, an autoregressive component was added to each model. It was demonstrated that the fuzzy logic model outperformed the traditional Ricker stock–recruitment model, the Ricker model with PDO as covariate and the neural network model as measured by several diagnostic criteria. In addition, the simple Ricker stock–recruitment model corrected with the autoregressive time series residuals outperformed the Ricker model with PDO as covariate, neural network model and fuzzy logic model ignoring the time series residuals. The importance of the PDO to halibut recruitment is discussed in terms of developing a harvest policy.

Evaluation of ageing accuracy of bocaccio ( Sebastes paucispinis) rockfish using bomb radiocarbon

The accuracy of bocaccio rockfish age assignments was evaluated using radiocarbon levels measured in otoliths collected from fish taken off the coast of Washington state (USA). Otoliths from 24 randomly selected fish with estimated birth years from 1950 to 1977, based on paired otolith age estimates, were used in this study. The level of radiocarbon measured in the core of each otolith was compared to a reference radiocarbon chronology based on radiocarbon levels in otoliths from known-age Pacific halibut. The degree of graphical phase correspondence between the two series was sufficient to support the hypothesis that the annuli were formed yearly in bocaccio otoliths but were somewhat difficult to identify. Statistical analysis of the ageing errors could not document a bias in production ageing of bocaccio. Pre-bomb radiocarbon levels measured in otolith cores confirm that bocaccio can live at least 37 years.

Seasonal migration and environmental conditions of Pacific halibut Hippoglossus stenolepis, elucidated from pop-up archival transmitting (PAT) tags

Pop-up archival transmitting (PAT) tags were used to study the fall migration of halibut in the Gulf of Alaska (GOA). We tagged 6 Pacific halibut Hippoglossus stenolepis on summer feeding grounds in the eastern GOA and another 6 in the western GOA from June 13 to August 6, 2002. The tags were programed to be released from the fish on January 15, 2003, at the height of the winter spawning season: 10 tags successfully detached, transmitted archived environmental data (depth and temperature), and generated accurate latitude-longitude coordinates shortly after pop-up; 2 tags deployed off SE Alaska were lost. The tags revealed that 6 fish had moved a considerable distance (>200 km) between tagging and pop-up, and all of these had moved northward to some extent. The longest of the observed migrations was from the southern Alaska Peninsula to Yakutat Bay, a linear displacement of 1153 km; 4 fish showed little evidence of geographic displacement, exhibiting migra- tions that ranged only from 30 to 69 km. Although 2 fish had moved inshore by the end of the tagging period, all other fish had moved offshore regardless of their overall migration distance. The precise timing of offshore movements varied, beginning as early as August and as late as January. These observations generally corroborate conventional tagging, indicating migration of halibut toward winter spawning grounds in the northern GOA, and movement of fish to deep water in fall. However, no single stereotypic migration behavior was apparent, and a variety of vertical movement patterns and temperature profiles were observed. Halibut spent most time in waters of 5 to 7°C, but experi- enced temperatures ranging from 2.6 to 11.6°C. Depth observations ranged from 0 to 736 m, with summertime activity concentrated in depths from 0 to 400 m, and halibut that exhibited offshore movement were typically observed at 300 to 700 m by mid-winter. Vertical movement (short-period changes in depth) varied among fish and over time, with some fish displaying little vertical activity, others displaying short periods of activity, and still others displaying considerable activity throughout their time at liberty.

An Econometric Market Model for the Pacific Halibut Fishery

The Alaska and British Columbia fishery for Pacific halibut has undergone substantial restructuring over the last decade, from a regulated open-access no-holds-barred derby that largely relied on frozen inventories to satisfy market demand, to a slow-paced individual quota-based fishery that has reorganized supply chains to deliver high-quality fresh product throughout a protracted season. We have developed a simultaneous equation model of the markets for Pacific halibut and used simulations based on our model to examine: (i) linkages between harvest and revenue; (ii) ex-vessel price and revenue-induced consequences of the Alaska IFQ program; (iii) likely ex-vessel price and revenue effects of the proposed elongation of the halibut season; and (iv) potential effects of the emergence of competing supplies from halibut aquaculture.

Behavioral responses to food odor in juvenile marine fish: Acuity varies with species and fish length

This study tested the hypothesis that acuity of behavioral responses to food odor in three commercially important species of marine fish would increase as juvenile length increased. Swimming activity among two size groups of fish was measured in the presence of a series of squid extract dilutions. Increased swimming activity in juvenile Pacific halibut Hippoglossus stenolepis Schmidt, walleye pollock Theragra chalcogramma Pallas, and sablefish Anoplopoma fimbria Pallas was stimulated above threshold concentrations of squid extract, expressed as dilution from full strength. Maximum chemosensory acuity was observed in smaller (8–14 cm total length, TL) Pacific halibut and walleye pollock, while larger sablefish (15–23 cm TL) continued to develop acuity. Response thresholds were highest (10 − 3 dilution) in Pacific halibut, at intermediate levels (10 − 4–10 − 6 dilution) in walleye pollock and smaller sablefish and reached the lowest levels (10 − 13 dilution) in larger sablefish. The widely held view that dissolved free amino acids (DFAA) are the primary chemosensory stimulants for fish food searching may not be valid for sablefish, as they detected squid extract at dilutions containing DFAA that appeared to be far below ambient sea water DFAA concentrations.

Use of high-frequency imaging sonar to observe fish behaviour near baited fishing gears

A high-frequency imaging acoustic camera was used to observe the behaviour of sablefish ( Anoplopoma fimbria) and Pacific halibut ( Hippoglossus stenolepis) around baited fish pots and baited hooks in the deep shelf environment (220–366 m depth) off Oregon. The acoustic camera, tested to a distance of 9.7 m (11.5–15.6 m 2 field of view), provided continuous high-resolution imagery of approaches of fish to the gear, entry into pot tunnels, bait attacks, and escapes in conditions of darkness and high turbidity. Fish inside and beyond the fish pot could also be observed. Fishes, including small individuals and “bait thieves” (>20 cm), could be measured and tracked in the digital images. Concurrent observations with a low-light video camera and infrared lighting yielded a field of view of approximately 1 m 2, limited to just one side of the fish pot. A large proportion of the video tape produced was unusable because of turbidity, and the patterns of fish movement around the pots and baited hooks were poorly characterized by the video camera. The large field of view provided by the acoustic camera showed that a very low percentage of sablefish and halibut approaching the gear were captured. Observations on different gear types, including fish pots with and without tunnel triggers, provide insights into how acoustic camera imagery can be used to improve our understanding of fish behaviour in the natural environment, to design increasingly selective and efficient fishing gear, and to improve bait-dependent stock assessments.

Identifying spawning behavior in Pacific halibut, Hippoglossus stenolepis, using electronic tags

Identifying spawning behavior in Pacific halibut, Hippoglossus stenolepis, is particularly challenging because they occupy a deep, remote environment during the spawning season. To identify spawning events, a method is needed in which direct observation by humans is not employed. Spawning behavior of seven other flatfish species has been directly observed in their natural environment by investigators using SCUBA. All of these flatfish species display almost identical spawning behavior that follows a routine. Therefore, it is reasonable to believe that this spawning behavior occurs in other flatfish species, including Pacific halibut. As part of a larger study, we recaptured two Pacific halibut on which Pop-up Archival Transmitting (PAT) tags had been attached during the winter spawning season. Because the tags were physically retrieved, we were able to collect minute-by-minute depth records for 135 and 155 days. We used these depth data to tentatively identify spawning events. On seven separate occasions between 20 January 2001 and 9 February 2001, one fish displayed a conspicuous routine only seen during the spawning season of Pacific halibut and the routine parallels the actions of other spawning flatfish directly observed by humans using SCUBA. Therefore, we propose this routine represents spawning behavior in Pacific halibut. The second tagged fish did not display the conspicuous routine, thus challenging the assumption that Pacific halibut are annual spawners. PAT tags may prove to be a useful tool for identifying spawning events of Pacific halibut, and that knowledge may be used for improved management in the future.

Fishing Rights or Fishing Wrongs?

Increasing attention is being paid to overfishing and the biological, economic, and social implications of persistent mismanagement of aquatic natural resources. In this chorus of concern, little attention is focused on sustainable fisheries, and the lessons to be learned from management systems that produce these successes. Although there is no one prescription for sustainability, a range of quota-based management tools have been used to eliminate the race for fish, increasing the incentives for long-term investment and efficiency. Variously referred to as fishing rights, tenure rights, or dedicated access privileges, quota-based fisheries confer a percentage (or quota) of the total allowable catch to named entities over some predetermined period, from short-term auction systems to intergenerational customary sea tenure. Whether a rights-based system stems from a traditional fishing rights system or has been recently introduced into modern commercial fisheries, achieving sustainability in the fishery is dependent on incentivizing the collective – from local communities to national fleets – to actively participate in self-regulation of the resource. Thus criticism of the approach often stems from the observation of the potential for cheating at the individual level (e.g., high grading, excessive discards), and the necessary exclusivity that accompanies any transition in management from open access to club membership. It is also worth noting that the resource in question – the fish – remain a public good, and as such, the public should be compensated – or at least not taxed – for their use. Thus the cost of fishery management, and the windfall profits of fishery conversion, should be shared. Rights-based management is not a silver bullet, and is probably not appropriate for all fisheries; however, the successes of the longline fisheries for Pacific halibut and sablefish in Alaska, the artisanal fisheries for loco in Chile and for spiny lobster in Mexico, and the Australian fisheries for Northern prawns and rock lobster, all clearly indicate that fishing rights should have a central place in the fisheries management toolbox.

Responses by Pacific Halibut to Air Exposure: Lack of Correspondence among Plasma Constituents and Mortality

AbstractAge‐1 and age‐2 Pacific halibut Hippoglossus stenolepis were exposed to a range of times in air (0–60 min) and air temperatures (10°C or 16°C) that simulated conditions on deck after capture to test for correspondence among responses in plasma constituents and mortality. Pacific halibut mortality generally did not correspond with cortisol, glucose, sodium, and potassium since the maximum observed plasma concentrations were reached after exposure to 30 min in air, while significant mortality occurred only after exposure to 40 min in air for age‐1 fish and 60 min in air for age‐2 fish. Predicting mortality in discarded Pacific halibut using these plasma constituents does not appear to be feasible. Lactate concentrations corresponded with mortality in age‐1 fish exposed to 16°C and may be useful predictors of discard mortality under a limited set of fishing conditions.

Age validation of canary rockfish (Sebastes pinniger) from off the Oregon coast (USA) using the bomb radiocarbon method

The alternating translucent and opaque banding pattern in canary rockfish (Sebastes pinniger) otoliths, aged using a break-and-burn methodology, are annual markings. To validate age assignment, we compared measured radiocarbon levels in canary rockfish otolith cores with a reference chronology developed from known age Pacific halibut (Hippoglossus stenolepis). An average 2- to 3-year phase shift was detected between the canary rockfish and a Pacific halibut reference chronology that was likely the result of differences in the regional oceanography or underageing bias. The assumption of ageing bias consistency was tested with two sampling designs. The first design controled for age-related ageing error, and the second design related birth year to estimated age. No change in the magnitude of ageing bias as a function of age was detected.

Tracking flows of fisheries products: the case of Pacific halibut in the Canadian economy

Patterns of international trade may affect the sustainability of fisheries, and empirical studies of these effects would be facilitated by a better understanding of actual trade flows over time. We present a general conceptual model of flows of fisheries products, and apply it to examine the trade flows of Pacific halibut (Hippoglossus stenolepis) through the Canadian economy, as a pilot study for similar work at national and international levels. We present data on the flows of Pacific halibut into (landings and imports) and out of (exports) the Canadian economy from 1950 to 2001, in terms of quantity and value. We examine how the flows have changed over the study period due to several factors, including changes in biomass, the implementation of Exclusive Economic Zones, and the individual quota systems in BC and Alaska. We use our data to estimate annual Canadian consumption of Pacific halibut. Extending this approach to a broad range of species and countries will contribute to understanding how such flows are affected by fisheries management, how the benefits of fisheries and international trade in fisheries products are distributed within and between countries, and how international trade interacts with fisheries management to produce ecosystem effects and welfare gains or losses.

Compensatory growth, energy storage and behavior of juvenile Pacific halibut Hippoglossus stenolepis following thermally induced growth reduction

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 293:233-240 (2005) - doi:10.3354/meps293233 Compensatory growth, energy storage and behavior of juvenile Pacific halibut Hippoglossus stenolepis following thermally induced growth reduction Thomas P. Hurst1,*, Mara L. Spencer1, Susan M. Sogard1,2, Allan W. Stoner1 1Fisheries Behavioral Ecology Program, Alaska Fisheries Science Center, National Marine Fisheries Service, NOAA, Hatfield Marine Science Center, Newport, Oregon 97365, USA2Present address: Southwest Fisheries Science Center, National Marine Fisheries Service, NOAA, 110 Shaffer Road, Santa Cruz, California 95060, USA *Email: thomas.hurst@noaa.gov ABSTRACT: For fishes settling over wide areas, spatial temperature variation can have a significant impact on growth rates during the early juvenile period. Size variation within cohorts and across years will depend on the thermal sensitivity of growth rate, the ability to move to favorable growth environments, and the potential to compensate for periods of reduced growth. We examined the growth, behavior and energy storage responses of juvenile Pacific halibut Hippoglossus stenolepis exposed to a thermally induced reduction in growth. Halibut reared for 12 wk at 2°C then acclimated to and grown at 10°C (delayed treatment) were compared to fish reared continuously at 10°C (controls). Growth rates at 2°C were 25% of those at 10°C, resulting in a 2.4-fold difference in mass after 12 wk. Following acclimation to 10°C, specific growth rates of delayed fish were 20% higher than controls. Complete compensation would have required 35 wk, assuming maintenance of observed growth rate differences between treatments. Rapid growth during the compensation phase was probably due in part to a reduction in the allocation of energy to lipid storage: length-corrected lipid levels of delayed fish were 14% lower than levels among control fish. Behavioral observations indicated that growth compensating fish were more active than control fish; this is assumed to reflect increased foraging activity. However, when presented with food, growth-compensating halibut did not initiate feeding more rapidly than control fish. The predation and starvation risks associated with increased activity and decreased energy storage appear to represent trade-offs with rapid compensatory growth in juvenile halibut. KEY WORDS: Pacific halibut · Hippoglossus stenolepis · Thermal variation · Compensatory growth · Energy storage · Behavior Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 293. Online publication date: June 02, 2005 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2005 Inter-Research.

Nonparametric estimates of age misclassification from paired readings

With a large enough sample, age misclassification probabilities can be estimated nonparametrically by fitting the observed distribution of differences between paired readings. Application of this procedure to Pacific halibut data reveals that the unsigned deviations of single readings from the mode follow a geometric distribution, leading to a simple specification of misclassification probabilities. The potential for bias in this and other published procedures is discussed.

Temperature and state‐dependence of feeding and gastric evacuation in juvenile Pacific halibut

Relationships between nutritional state, behavioural response to prey and gastric evacuation rates were examined in juvenile Pacific halibut Hippoglossus stenolepis feeding on squid. Pacific halibut reared at 2, 6 and 10° C were fasted for 1 or 7 days to generate variation in energetic state. The 7 day fast resulted in measurable declines in condition indices at 10 and 6° C but not at 2° C. At 10° C, all Pacific halibut consumed the first meal offered, but fish previously fasted for 7 days took significantly longer to locate and consume the meal than fish fasted for only 1 day. At 2° C, Pacific halibut fasted for 7 days did not generally consume the first meal offered, but resumed feeding 2·1 days sooner, on average, than fish fasted for only 1 day. The gastric evacuation rate of the squid meal was best described by a power model with near‐exponential curvature (a = 1·011). The evacuation rate was strongly temperature‐dependent (Q10 = 3·65) but displayed the same degree of variability at each temperature. The evacuation rate in Pacific halibut was not affected by feeding history, body size or energetic state. Furthermore, individual variation in gastric evacuation rate was not correlated with feeding responsiveness at any temperature. These results indicate a general plasticity in the behavioural but not physiological aspects of energy acquisition.

Fish density and size alter Pacific halibut feeding: implications for stock assessment

Laboratory experiments were conducted with Pacific halibut Hippoglossus stenolepis to test the hypothesis that responsiveness to food cues is density‐ and size‐ dependent. Tanks holding one, two and four fish were video‐taped continuously before and after introduction of an olfactory cue and whole baits (squid). Pre‐cue indices of activity did not vary with fish density. After olfactory stimulation, per capita activity was directly related to density, with no significant increase in activity by single fish. Numbers of baits located, attacked and consumed were directly related to fish density, and average times to first attack varied from 12 s in groups of four fish to >15 min in single fish. The latency period between location and attack decreased significantly with fish density. When large (43–55 cm, total length, LT) and small (31–38 cm LT) Pacific halibut were tested together in pairs and groups of four fish, small individuals located baits first in 61% of the trials. Large fish, however, consumed all of the baits (except one) in trials where both large and small fish responded. Social facilitation in Pacific halibut feeding will result in a non‐linear relationship between catch per unit effort and population density, and the size composition of fish captured may be influenced by interference competition.