Sablefish Anoplopoma Fimbria Research Articles

In Search of Optimal Harvest Rates for West Coast Groundfish

In this paper, I explore how patterns of compensatory mortality, as assessed through stock–recruitment relationships, may influence optimal harvest rates and relative yields for several West Coast groundfish stocks. To do this, I revisited Clark's (1991) groundfish life history model and maximin (i.e., maximize the minimum) yield approach to evaluate target harvest rates for five stocks (Dover sole Microstomus pacificus, lingcod Ophiodon elongatus, sablefish Anoplopoma fimbria, Pacific hake Merluccius productus, and widow rockfish Sebastes entomelas) using recent estimates of fishery and life history parameters and stock–recruitment data. I found that a spawning-stock-per-recruit target of roughly 35% of its unfished amount would be reasonable for these stocks if Clark's assumed stock–recruitment parameters are representative and the policy goal is a maximin yield. In contrast, use of estimated stock–recruitment parameters suggested more conservative percentages of the unfished spawning stock per recruit and more conservative harvest rate targets for most stocks. A key implication of this work is that Clark's groundfish life history model is sensitive to the stock–recruitment shape parameters. As a result, these parameters should be estimated where possible or imputed using results from meta-analyses. Overall, a conservation target of roughly 35% of the unfished spawning stock per recruit is very likely too low for lingcod, sablefish, and widow rockfish stocks under current environmental conditions, but it may be adequate for Dover sole and Pacific hake stocks.

Contrasts in the capacity and underlying mechanisms for compensatory growth in two pelagic marine fishes

The widespread capacity for teleost fishes to engage in compensatory growth suggests there are costs or trade-offs that constrain normal growth to sub-maximal rates. Some potential trade- offs include behavioral conflicts between foraging and avoiding predators, and physiological aspects of energy allocation between synthesis of new tissue and functional demands of metabolism and maintenance. We examined the capacity for compensation and some potential underlying mecha- nisms in juveniles of 2 northern Pacific fish species, walleye pollock Theragra chalcogramma and sablefish Anoplopoma fimbria. Fish were deprived of food for 2 to 3 wk, then returned to ad libitum rations. Growth rates were subsequently compared to those for continually fed fish for up to 16 wk, and potential trade-offs in behavior (food consumption, routine swimming speeds, and response to a predator) and physiology (indexed by critical swimming speeds) were examined during 3 time peri- ods: immediately after deprivation, after 4 wk of ad libitum rations, and after 9 wk. We distinguished between routine swimming speeds, which indicate volitional motor activity, and critical swimming speeds, which estimate physiological capacity by forcing fish to swim to exhaustion against an increasing current. Previously deprived walleye pollock exhibited a clear, sustained capacity for accelerated growth, allowing them to quickly catch up in size to continually fed fish. Sablefish, how- ever, exhibited only a minor level of growth compensation. Underlying mechanisms of compensatory growth also differed between the 2 species. Previously deprived walleye pollock increased food con- sumption to levels 3 to 4× greater than those of control fish and reduced energy expenditure by low- ering routine swimming speeds. Compensating sablefish did not differ from control fish in consump- tion rates or routine swimming, but had lower critical swimming speeds than control fish, suggesting a trade-off in energy allocation. Responses to a simulated predator threat did not differ between pre- viously deprived and continually fed fish of either species. The experimental results are suggestive of different mechanisms, behaviorally based for walleye pollock and physiologically based for sablefish, associated with accelerated growth. The differences between the 2 species in integrated processes of growth, behavior, and physiology are likely to be a function of their contrasting life history strategies and different baseline growth rates.

Growth and behavioral responses to elevated temperatures by juvenile sablefish Anoplopoma fimbria and the interactive role of food availability

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 217:121-134 (2001) - doi:10.3354/meps217121 Growth and behavioral responses to elevated temperatures by juvenile sablefish Anoplopoma fimbria and the interactive role of food availability Susan M. Sogard*, Bori L. Olla Alaska Fisheries Science Center, National Marine Fisheries Service, Hatfield Marine Science Center, Newport, Oregon 97365, USA *E-mail: susan.sogard@noaa.gov ABSTRACT: Larval and age-0 sablefish Anoplopoma fimbria reside in neustonic waters of the North Pacific during spring and summer. We estimated the potential impacts of elevated surface temperatures on ecological processes of growth, conversion efficiency, and behavior in early juvenile sablefish. Growth experiments tested a wide range of temperatures from 6 to 24°C, with fish receiving ad libitum or low (3% body weight d-1) rations. With unlimited food, growth increased rapidly as temperature increased to 14°C, then displayed a more gradual rise to 22°C. Growth rates at the warmer temperatures were among the highest recorded for teleosts, attaining a maximum of 3.3 mm d-1 in length and a specific growth in weight of 11.8%. A similar response to temperature was observed at low rations, although at lower overall growth rates. At 24°C, there was a severe decline in growth for both ration levels, and few fish survived the 3 wk experiments. Gross growth efficiency, measured at temperatures of 6 to 22°C, displayed an interactive effect of temperature with ration level consistent with bioenergetic relationship. Conversion peaked at 16 to 20°C for fish receiving ad libitum rations, and at 10°C for fish on restricted rations. Conversion rates of sablefish were comparable to those calculated for a diverse array of fish species, suggesting that the rapid growth rates are driven by high consumption rather than unusually efficient energy transfer. Experiments analyzing sablefish behavior in thermally stratified water columns demonstrated increasing movement into colder water as ration level decreased, in agreement with an energy conserving strategy. Average monthly temperatures within the major nursery areas of neustonic juveniles (north of 40°N) did not exceed 19°C during the last 19 yr. These results suggest that juvenile sablefish are capable of tolerating and thriving at increased temperatures, with the critical caveat that sufficient food resources must be available. Thus, impacts on early life stages exerted by El Niño conditions, oceanographic regime shifts, or climate changes induced by current global warming scenarios are likely to be a consequence of indirect effects on circulation and productivity patterns rather than direct effects of warmer temperatures. However, because the upper thermal limit for growth nearly coincides with the upper limit for survival, exhibiting a sharp demarcation between favorable growth conditions and intolerable temperatures, juvenile sablefish at the southern limit of their distribution may suffer the direct effects of elevated temperature; recruitment of juveniles to southern populations may become more sporadic if the frequency of warming events increases with climate change. KEY WORDS: Growth efficiency · Temperature selection · Ration · Activity Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 217. Online publication date: July 31, 2001 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2001 Inter-Research.

Stress induced by hooking, net towing, elevated sea water temperature and air in sablefish: lack of concordance between mortality and physiological measures of stress

In a series of laboratory studies designed to simulate bycatch processes, sablefish Anoplopoma fimbria were either hooked for up to 24 h or towed in a net for 4 h and then subjected to an abrupt transfer to elevated sea water temperature and air. Mortality did not result from hooking or net towing followed by exposure to air, but increased for both capture methods as fish were exposed to elevated temperatures, reflecting the magnifying effect of elevated temperature on mortality. Hooking and exposure to air resulted in increased plasma cortisol and lactate concentrations, while the combination of hooking and exposure to elevated temperature and air resulted in increased lactate and potassium oncentrations. In fish that were towed in a net and exposed to air, cortisol, lactate, potassium and sodium concentrations increased, but when subjected to elevated temperature and air, no further increases occurred above the concentrations induced by net towing and air, suggesting a possible maximum of the physiological stress response. The results suggest that caution should be exercised when using physiological measures to quantify stress induced by capture and exposure to elevated temperature and air, that ultimately result in mortality, since the connections between physiological stress and mortality in bycatch processes remain to be fully understood.

Effects of Group Membership and Size Distribution within a Group on Growth Rates of Juvenile Sablefish Anoplopoma fimbria

Group membership can confer both advantages and disadvantages to growth in juvenile fishes. The balance between costs and benefits of social interactions can shift depending on such factors as the composition of the group (density and size disparity) and the availability of food. We examined the effect of these factors on absolute growth and growth depensation in juvenile sablefish, Anoplopoma fimbria. Increasing density and increasing size disparity had little influence on absolute growth rates of juvenile sablefish and the effects of these social factors were not modified by ration level. In experiments testing density effects, absolute growth did not differ among groups of 1, 3, or 10 fish held at high rations, but at low rations single fish exhibited a different pattern of size-dependent growth compared to fish in groups. In experiments testing disparity effects, absolute growth did not differ between groups with an even size distribution and groups with a mixed size distribution. The relative size of an individual within a group, i.e., small, medium, or large, also did not modify growth, despite evidence of higher chasing behavior in mixed size distributions. Although the growth of small fish was not diminished in the presence of large fish, negative impacts of size disparity were expressed in high levels of cannibalism, which occurred in 42% of groups with a mixed size distribution. Significant growth depensation over time occurred in the density experiment, but not in the size disparity experiment, possibly due to the shorter duration of the latter experiment. We suggest that growth depensation was generated by individual variability in growth capacity rather than social effects on growth rates. Schooling behavior, measured by group cohesion indices, increased with fish size and was higher in groups with an even vs. a mixed size distribution. These results for sablefish are consistent with other schooling species in which growth variability is determined by exploitative competition and/or genetic variability in growth capacity rather than interference competition.

Temperature magnified postcapture mortality in adult sablefish after simulated trawling

For sablefish Anoplopoma fimbria that had been transferred abruptly from ambient (5·7° C) to temperatures ranging from 15 to 20° C for 30 min followed by 15 min in air (19·5) C), mortality increased with temperature. Mortality occurred at lower temperatures for sablefish that were net‐towed for 4 h at ambient temperature before exposure to a rapid increase in temperature. A clear relationship was apparent between serum lactate and temperature with lactate increasing as temperature increased. For treatments in which mortality did not occur, lactate decreased sharply within 24 h, suggesting recovery. It would appear that the critical postcapture temperature for sablefish that reside and are captured at 4‐6° C, would be between 12 and 15° C. The results of this study suggest that fishery management strategies designed to increase postcapture survival of sablefish bycatch should include a consideration of the impact of exposure to seasonal thermoclines and seasonally elevated air temperatures.

Temperature magnified postcapture mortality in adult sablefish after simulated trawling

For sablefish Anoplopoma fimbria that had been transferred abruptly from ambient (5·7° C) to temperatures ranging from 15 to 20° C for 30 min followed by 15 min in air (19·5) C), mortality increased with temperature. Mortality occurred at lower temperatures for sablefish that were net-towed for 4 h at ambient temperature before exposure to a rapid increase in temperature. A clear relationship was apparent between serum lactate and temperature with lactate increasing as temperature increased. For treatments in which mortality did not occur, lactate decreased sharply within 24 h, suggesting recovery. It would appear that the critical postcapture temperature for sablefish that reside and are captured at 4-6° C, would be between 12 and 15° C. The results of this study suggest that fishery management strategies designed to increase postcapture survival of sablefish bycatch should include a consideration of the impact of exposure to seasonal thermoclines and seasonally elevated air temperatures.

Analysis of Fishing Power Correction Factor Estimates from a Trawl Comparison Experiment

Four published analytical techniques were applied to comparative trawl data to obtain fishing power correction (FPC) factors for 12 major commercial species that were caught by two resource assessment trawls used by the National Marine Fisheries Service (Alaska Fisheries Science Center). Fishing power correction techniques included ratios of catch per unit effort (CPUE), randomized block analysis of variance (ANOVA), standard least-squares regression, and a method developed by Kappenman. All four estimators generally gave similar results for species that were clearly caught in higher proportion by one trawl, but they differed in the magnitude of the adjustment. For Pacific cod Gadus macrocephalus and sablefish Anoplopoma fimbria, which were caught at very similar rates during the experiment, FPC estimates close to 1.0 (no difference between trawls) were obtained from each technique, but they differed regarding which trawl was most efficient. The Kappenman estimator gave FPC estimates of 1.0 for six species. Whenever this estimator did recognize a fishing power difference, it was always in the same direction given by the other techniques. However, the magnitude of the FPC estimate obtained from the Kappenman method was usually less than or equal to those obtained from the other methods. In addition, the Kappenman method does not require a comparative trawling experiment, as do the other methods, which are extremely costly to management agencies in terms of days at sea. Also discussed are sample size requirements and the use of 95% confidence intervals as criteria to decide if a FPC should be applied.

Effects of simulated trawling on sablefish and walleye pollock: the role of light intensity, net velocity and towing duration

Laboratory apparatus which simulated capture of fish in the cod‐end of a towed trawl was used to induce post‐capture stress as measured by alterations in behavioural, physiological and mortality indices in juvenile walleye pollock Theragra chalcogramma and juvenile and adult sablefish Anoplopoma fimbria. Differences in resistance to net entrainment varied between species with the severity of stress and the potential for recovery depending on light intensity, net velocity and towing duration. At a light intensity which simulated daylight at depth in clear ocean water (0.5 μmol photons m−2 s−1), walleye pollock juveniles were able to maintain swimming in nets towed at 0.65 m s−1 for 3h with no discernible effects on behaviour or mortality. However, when net velocity was increased to >0.75m s−1 or light intensity was decreased to <0.002 μmol photons m−2 s−1, fish became entrained in the meshes of the net and exhibited significant alterations in feeding behaviour, predator evasion and increases in plasma cortisol concentrations. Marked increases in stress‐induced mortality also occurred, in some cases after a delay of 6 days and eventually reaching 100%. In comparison with walleye pollock, sablefish juveniles became entrained in the meshes of the net at higher velocities (>0.92m s−1) or lower light intensities (<0.0004 μmol photons m−2 s−1) and were much more resistant to post‐capture stress. Towing of net‐entrained fish for 15 min caused no detectable changes in feeding and cortisol and for 2 h, no changes in feeding although mortality increased from 0% for 15‐min tows to 19% for 2‐h tows. Towing for 4 h caused significant alterations in feeding and cortisol with feeding recovering to control levels by 6 days and cortisol by 3 days; mortality was 25%. When adult sablefish were towed for 4 h followed by 15‐min exposure to air, feeding was inhibited 6 days after towing, but recovered within 30 days with no mortality observed after 30 days. The results demonstrate the value of using laboratory‐based behavioural and biochemical indices to identify factors that may potentially affect post‐capture survival among different species of fish.

Effects of simulated trawling on sablefish and walleye pollock: the role of light intensity, net velocity and towing duration

Laboratory apparatus which simulated capture of fish in the cod-end of a towed trawl was used to induce post-capture stress as measured by alterations in behavioural, physiological and mortality indices in juvenile walleye pollock Theragra chalcogramma and juvenile and adult sablefish Anoplopoma fimbria. Differences in resistance to net entrainment varied between species with the severity of stress and the potential for recovery depending on light intensity, net velocity and towing duration. At a light intensity which simulated daylight at depth in clear ocean water (0.5 μmol photons m−2 s−1), walleye pollock juveniles were able to maintain swimming in nets towed at 0.65 m s−1 for 3h with no discernible effects on behaviour or mortality. However, when net velocity was increased to >0.75m s−1 or light intensity was decreased to <0.002 μmol photons m−2 s−1, fish became entrained in the meshes of the net and exhibited significant alterations in feeding behaviour, predator evasion and increases in plasma cortisol concentrations. Marked increases in stress-induced mortality also occurred, in some cases after a delay of 6 days and eventually reaching 100%. In comparison with walleye pollock, sablefish juveniles became entrained in the meshes of the net at higher velocities (>0.92m s−1) or lower light intensities (<0.0004 μmol photons m−2 s−1) and were much more resistant to post-capture stress. Towing of net-entrained fish for 15 min caused no detectable changes in feeding and cortisol and for 2 h, no changes in feeding although mortality increased from 0% for 15-min tows to 19% for 2-h tows. Towing for 4 h caused significant alterations in feeding and cortisol with feeding recovering to control levels by 6 days and cortisol by 3 days; mortality was 25%. When adult sablefish were towed for 4 h followed by 15-min exposure to air, feeding was inhibited 6 days after towing, but recovered within 30 days with no mortality observed after 30 days. The results demonstrate the value of using laboratory-based behavioural and biochemical indices to identify factors that may potentially affect post-capture survival among different species of fish.

Standardizing sablefish (Anoplopoma fimbria) long-line survey abundance indices by modeling the log-ratio of paired comparative fishing cpues

From 1979 to 1994, the US National Marine Fisheries Service (NMFS) and the Fisheries Agency of Japan (FAJ, 1979‐1988), and later the North Pacific Cooperative Fisheries Company (NPCFC, 1989‐1994), have performed joint long-line surveys on chartered Japanese commercial fishing vessels in the Gulf of Alaska. These surveys were designed primarily to monitor the relative abundance of sablefish (Anoplopoma fimbria). To prepare for the future termination of these joint surveys, between 1988 and 1994 NMFS performed similar long-line surveys aboard US vessels in the Gulf of Alaska. These paired (i.e. duplicated) surveys from 1988 to 1994, provide a basis for comparing future NMFS survey results with the past time series of joint US and Japanese surveys (i.e. the joint 1979‐1994 surveys). This paper describes how modeling the log-ratio of paired cpue results (i.e. the log[(NMFS cpue)/(joint cpue)]), from a standardized survey design, was used to provide a basis for converting the joint survey cpue values to values directly comparable to those from the NMFS surveys. This was necessary because sablefish long-line surveys will be carried out solely by NMFS in the future.

Bathymetric Demography and Management of Dover Sole

Bathymetry is a key element in the demography of Dover sole Microstomus pacificus. Juvenile Dover soles begin life in relatively shallow water on the continental shelf but move gradually down the continental slope into deeper water as they grow and reach sexual maturity. Large and old individuals may eventually reach depths greater than 1,500 m. The ontogenetic migration of Dover soles into deeper water gives rise to a general pattern of increasing fish size with water depth, but there are differences between sexes and locations. To describe these patterns in greater detail, we computed probability distributions for depth, length, and sex using research trawl data for Dover sole taken off central California and Oregon. Our results indicate that females live at greater depths than do males and that abundance of large Dover soles may be lower at depths where lowest oxygen concentrations occur. In addition, major differences in bathymetric demography exist between study sites due, we suggest, to differences in bottom topography. We used one group of probability distributions and logbook data for Oregon and central California in a simple model to demonstrate how depth of fishing and bathymetric demography complicate interpretation of length composition and other data from a commercial fishery. Results from the model indicate that depth-stratified assessment models may be required to interpret fisheries data for Dover sole and other species, like shortspine thornyhead Sebastolobus alascanus and sablefish Anoplopoma fimbria that undergo ontogenetic migration from shallow into deep water.

Planning Models for Individual Transferable Quota Programs

This paper develops an approach to simulating markets for individual transferable quotas prior to their actual implementation. This approach is based on linear programming models for individual vessels that allow estimation of market derived demand for quota to simulate the expected equilibrium market price for quota and maximum quasi-rents for alternative quota allocations. The simulated price is an annual lease or rental price. The approach, applied to a sample of longline vessels targeting sablefish (Anoplopoma fimbria) in the Columbia INPFC area of the United States, indicates substantial potential gain in quasi-rent and economic efficiency from quota trade. The simulated quota exchange also indicates potential for concentration of quota. The quota market risks becoming thin, noisy, and hampered by noncompetitive forces, potentially requiring limits to quota transfer and concentration.

Mortality of Juvenile Sablefish Captured by Hand-Jigging and Traps

Abstract Capturing juvenile sablefish Anoplopoma fimbria with hand-jigs instead of traps and when water temperatures are relatively warm (late spring to autumn in southeastern Alaska) reduces tagging mortality. After 1 week in holding tanks, mortality of hand-jigged sablefish was 19%, whereas mortality of fish caught by traps was 75%. Myxobacteriosis may have contributed to mortality. This disease was initiated by handling stress and mechanical injury; its signs included grey, saddle-shaped lesions, hemorrhaging of the ventral abdomen and fins, and caudal fin erosion. Greater survival of hookcaught juvenile sablefish in summer than in winter may have been due to less favorable conditions for the bacteria during warmer water temperatures.

Short communication: Induced ovulation of sablefish (Anoplopoma fimbria) following oral administration of des Gly10-(D-Ala6)LH-RH ethylamide

Short communication: Induced ovulation of sablefish (Anoplopoma fimbria) following oral administration of des Gly10-(D-Ala6)LH-RH ethylamide

Effect of an External Tag on Growth of Sabiefish (Anoplopoma fimbria), and Consequences to Mortality and Age at Maturity

Tagged juveniles from a strong year-class of sablefish (Anoplopoma fimbria) were sampled for 9 yr Tagged females were approximately 6 cm larger than untagged females at 50% maturity. Males showed little difference because of their slower growth rate. Untagged males and females matured one and 2 yr earlier than tagged males and females. From this same year-class length-at-age of untagged males and females was significantly larger than for tagged and recaptured fish. Untagged males and females were 6.5 and 8 cm larger than tagged fish by age seven. Smaller tagged fish were recaptured at lower rates than larger tagged fish, indicating that slower growth reduced recapture percentage, which we believe indicates a higher mortality rate. Because smaller size was associated with increased mortality and tagged fish grew slower than untagged fish, we concluded that tagged fish had higher rates of mortality than untagged fish. The increased age and size at 50% maturity and the increased juvenile mortality indicated the potential response of a population of sablefish and possibly other species to a reduction in individual fish growth. If our results apply to other species and other types of tags, investigators should be cautious in extrapolating from tagged to untagged populations.

Effects of Extended Jurisdiction on Management and Conservation of Canada's Pacific Coast Fisheries

In 1977, Canada extended its fisheries jurisdiction to 370 km (200 nautical miles), which obligated the Department of Fisheries and Oceans to make annual assessments of the actual and potential productivity of stocks occurring within the zone. This paper examines some of the effects of the management schemes that have been developed for marine fish resources in waters off British Columbia. Management options are briefly discussed. For most species, restrictions in the form of total allowable catches have been recommended. Other management recommendations have included mesh regulations, minimum sizes, closures, and gear controls. Extended jurisdiction also afforded an opportunity to implement alternative management regimes for stocks, particularly integration of management with research on population dynamics. The exercise of making management recommendations implies that characteristics of fish populations on the grounds have been reasonably estimated. We discuss the use of survey data and landing statistics for assessing stocks in the extended fishing zone. Models used to evaluate the effects of different management options are also discussed. We note the results of alternative management programs, such as assemblage management and managing fishing mortality. Case studies providing insights into how stock management has been improved in British Columbia are described for two broad production systems, one for long-lived, low-production stocks such as rockfish Sebastes spp. and sablefish Anoplopoma fimbria and a second one for short-lived, high-production stocks such as Pacific hake Merluccius productus and Pacific herring Clupea harengus pallasi.

Analyzing Relative Abundance Indices with Log-Linear Models

Abstract Log-linear models are proposed for the problem of simultaneously analyzing relative abundance indices available from different survey techniques over different areas and years. I show why analysis on the untransformed (original) scale is inappropriate, and why analysis on the logarithmic scale allows for a generally consistent theory. Models for estimating both annual abundance indices (two-way analysis of variance), and trends in annual abundance (analysis of covariance) are considered. The methods are illustrated by analyzing data from the Japanese commercial longline fishery for sablefish Anoplopoma fimbria in the gulf of Alaska.

Effectiveness of Experimental Escape Mechanisms in Sablefish Traps

Abstract Experiments comparing the efficiency of escape mechanisms were conducted with conical traps for sablefish Anoplopoma fimbria. A 20-cm slash in the trap wall, a square 30.5-cmdiagonal panel, and an 18-cm-high triangular panel fastened with a corrodible “time-release” device (magnesium alloy cylinder) were tested. The effectiveness of the escapement mechanisms in the traps was 56% with the 20-cm slash, 99% with the square panel, 90% with the triangular panel equipped with the “time-release” device, and 99% with the triangular panel left in the open position. Cotton butcher's twine is recommended as a binding material for escape panels because, among six bindings tested, butcher's twine disintegrated fastest. Cotton butcher's twine reached a 0-kg breaking strength in 31 d and disintegrated in 46 d. Estimates of annual sablefish loss in traps lost on the grounds during 1977–1983 ranged from 73 to 1,331 tonnes and annual harvests ranged from 1,085 to 4,409 tonnes.

Aging discrepancy related to asymmetrical otolith growth for sablefish Anoplopoma fimbria in northern California.

Otoliths (sagittae) were removed from a sample of 801 sablefish collected at sea from commercial otter trawl vessels in northern California from April through August 1984. This study presents a detailed examination of aging discrepancies between a) surface and b) broken and burnt (section) otolith aging methods, and considers possible mechanisms responsible for discrepancies. Sablefish age assignments based on the broken and burnt (section) aging method were higher than those based on surface aging for fish exceeding about 5-7 years section age. Beyond these ages, discrepancies increased with increasing section ages. The surface aging method assumes that there will be continual radial growth with increasing fish age, but otolith radius measurements showed that rate of radial growth dramatically decreased with increasing age and made surface aging unreliable for all but young fish. In contrast, otolith thickness measurements increased linearly with increasing section age and were highly correlated with section ages. When growth in length becomes slow, then surface ages are probably not accurate and discrepancies between surface and section ages dramatically increase with increasing section age.