Fish Size and Exposure to Air: Potential Effects on Behavioral Impairment and Mortality Rates in Discarded Sablefish Michael W

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North American Journal of Fisheries Management Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/ujfm20 Fish Size and Exposure to Air: Potential Effects on Behavioral Impairment and Mortality Rates in Discarded Sablefish Michael W. Davis a & Steven J. Parker b a Alaska Fisheries Science Center, National Oceanic and Atmospheric Administration, Fisheries Service, Hatfield Marine Science Center, Newport, Oregon, 97365, USA b Oregon Department of Fish and Wildlife, Hatfield Marine Science Center, Newport, Oregon, 97365, USA Available online: 09 Jan 2011

To cite this article: Michael W. Davis & Steven J. Parker (2004): Fish Size and Exposure to Air: Potential Effects on Behavioral Impairment and Mortality Rates in Discarded Sablefish, North American Journal of Fisheries Management, 24:2, 518-524 To link to this article: http://dx.doi.org/10.1577/M03-030.1

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Fish Size and Exposure to Air: Potential Effects on Behavioral Impairment and Mortality Rates in Discarded Sable®sh

MICHAEL W. D AVIS* Alaska Fisheries Science Center, National Oceanic and Atmospheric Administration, Fisheries Service, Hat®eld Marine Science Center, Newport, Oregon 97365, USA

STEVEN J. PARKER Oregon Department of Fish and Wildlife, Hat®eld Marine Science Center, Newport, Oregon 97365, USA

Abstract.ÐFisheries models often assume that discarded undersized ®sh and target species will survive and contribute to future recruitment and yield. If smaller ®sh are more susceptible to capture stressors than larger ®sh, then the assumption that smaller discards would contribute to recruitment may not be true. We tested the hypothesis that small sable®sh Anoplopoma ®mbria show more behavioral impairment and mortality than large ®sh when exposed to air (10±60 min) at various temperatures (10±18ЊC). Sable®sh captured by trawl, longline, or trap are commonly exposed to these conditions during warmer seasons when brought up on deck and sorted. Two size-classes of ®sh (small: 32±49 cm total length [TL]; large: 50±67 cm TL) were used in the experiments. Behavior was measured as upright orientation and startle responses to visual and mechanical stimuli 1, 2, 3, and 24 h after air exposure; mortality was measured through 7 d after air exposure. Small ®sh mortality increased as air time increased and was at higher levels than in large ®sh. Only 10 min of air exposure caused behavioral impairment in small and large ®sh, which could lead to increased predation on discarded ®sh. At 24 h after air exposure, normal behavior had not generally resumed and small ®sh had more behavioral impairment than large ®sh.

Size-related mortality and its causes in discard- predation becoming a signi®cant source of delayed ed ®sh, with smaller ®sh showing greater mortality mortality. than larger ®sh, is an important factor to consider Sable®sh is a highly valued species that is sub- in models of ®sheries recruitment and yield. Fish- jected to an intense commercial ®shery off Alaska, eries management often relies on minimum size British Columbia, Washington, Oregon, and Cal- rules for harvest, with the assumption that dis- ifornia, with landings of 26,240 metric tons (mt) carding of undersized ®sh will contribute to future in 2000, worth an estimated US$82 million ex- recruitment and yield (Halliday and Pinhorn vessel (FAO 2002). The current discard rate of 2002). Target species may also be subjected to sable®sh in trawl ®sheries off the U.S. West Coast ``highgrading'' in which smaller ®sh are discarded is estimated to be 21% of total sable®sh catch by for economic reasons. If mortality rates of dis- weight and 85% by number (Schirripa and Methot carded smaller ®sh are high, the bene®ts in future 2001). Mortality of sable®sh discards from trawl growth or reproductive potential are thwarted (Pin- Downloaded by [Oregon State University] at 17:07 22 August 2011 ®sheries is assumed to be 100%, while no mortality horn and Halliday 2001). While size-related mor- is assumed for discard from longline and trap ®sh- tality has not been investigated in sable®sh Ano- eries (Schirripa and Methot 2001). Studies of cap- plopoma ®mbria, smaller ®sh of other species have ture-related stressor effects have indicated that been observed to have higher discard mortality these mortality assumptions are not realistic. In rates than larger ®sh under ®eld conditions (Neil- warmer months of the year, there is a high prob- son et al. 1989; Richards et al. 1995; Milliken et ability that during ®xed-gear retrieval and landing al. 1999; Parker et al. 2003) and laboratory con- on deck, sable®sh discards would be subjected to ditions (Davis and Olla 2002). Size-related behav- abrupt increases in water and air temperature ioral impairment in discards, in which normal be- which would be expected to produce a range of havior is decreased or completely inhibited, has discard sable®sh behavioral impairment and mor- not been studied in any detail and may result in tality rates in ®xed-gear ®sheries (Davis et al. 2001; Davis 2002). The assumption of 100% mor- * Corresponding author: [email protected] tality in trawl ®sheries may not be realistic given Received February 12, 2003; accepted July 28, 2003 the relative hardiness of sable®sh to capture in nets

518 SIZE-RELATED DISCARD MORTALITY 519

during cooler seasons (Davis et al. 2001; Davis 2002). Sable®sh move to deeper waters as they age (Methot 1992), so the size composition of sable®sh catch is related to the depth of the ®shery. In ad- dition, sable®sh are discarded in trap, longline, and bottom trawl ®sheries for other species because of size or catch limits, or minimum market size (Ack- ley and Heifetz 2001; PFMC 2002). In 2002, the size limit for sable®sh captured in trawl ®sheries off California was 56 cm (PFMC 2002). The estimated size at 50% selection is approximately 40 cm for trawl gear and 50 cm for trap and longline gears (Schirripa and Methot 2001). In Washington,

Oregon, and California trawl ®sheries, all esti- FIGURE 1.ÐLength frequency of sable®sh in two size- mated discards were less than 48 cm, with an av- classes (small [Ͻ50 cm]: N ϭ 108; and large [Ն50 cm]: erage total weight of 566 and 547 metric tons in N ϭ 108) used in air time and temperature experiments. 2000 and 2001, respectively. For landed catch, prices paid for sable®sh depend on the size of the ®sh. This price structure creates an incentive to 13ЊC, 30±32 g/L salinity, O Ͼ 90% saturation) retain larger ®sh and discard smaller ®sh (Schirripa 2 and fed 6% body weight on chopped dead market and Methot 2001) and to capture even more ®sh squid Loligo opalescens three times per week. For and discards than necessary in the process. The the remaining time, ®sh were reared in circular seasonality of ®sheries (occurring mainly in sum- tanks (4.5 m diameter, 1.0 m depth, 15,904 L vol- mer months), minimum size limits, and economic ume) supplied with seawater (20 L/min, 7.5±8.5ЊC, incentives to select for larger ®sh can result in 30±32 g/L salinity, O Ͼ 90% saturation) and fed smaller ®sh being discarded at high rates in most 2 6% body weight on whole dead squid twice per ®sheries and, consequently, in high discard mor- week. A total of 108 (32±49 cm TL) age-1 juvenile tality rates. ®sh and 108 (50±67 cm TL) age-2 juvenile ®sh The aim of this laboratory study was to test the were used once in experiments (Figure 1). Fish hypothesis that small sable®sh have more behavioral impairment and mortality than large ®sh as age was determined by holding age-0 ®sh for a a result of exposure to air for various times and known period of time. All ®sh lengths were mea- temperatures which are often present in trawl, sured after conducting air exposure experiments. longline, and pot ®sheries when ®sh are brought Air exposure.ÐSable®sh were exposed to air at on deck and sorted. Stress responses to air con- three temperatures for various periods of time, ditions are a conservative estimate of stress in dis- similar to the exposure that would occur on the carded ®sh because stressors associated with other deck of a ®shing vessel. For sable®sh, air exposure factorsÐincluding physical injury from capture, is a function of handling time on deck and can Downloaded by [Oregon State University] at 17:07 22 August 2011 pressure changes, and hypoxia in piles of ®sh on range from a few minutes when catches are small boardÐare not included (Davis et al. 2001; Davis (hook and line, trap, and trawl) to greater than 60 2002). Such additional capture stressors would be min when catches are large (trawl), while air tem- expected to increase stress responses and mortal- perature on deck in the summer can range up to ity, but not to alter the basic principles of stress 25ЊC. The ®sh were transferred by dip net from a response related to size. holding tank into empty rectangular tanks (90 ϫ 60 ϫ 30 cm) in temperature-controlled rooms. Two Methods age-classes (size-classes) were exposed to air at Juvenile age-0 sable®sh (20±40 mm total length 10, 14 and 18ЊC for 10, 20, 30, 40, 50, and 60 [TL]) were captured in the spring from the neuston min. A total of 18 treatments (3 air temperatures offshore from Newport, Oregon, and reared in the ϫ 6 air times) were administered using six ®sh per laboratory for up to 2 years prior to experiments. treatment, held together in a rectangular tank. Af- For the ®rst year of rearing, ®sh were held in cir- ter a stressor treatment, the six treatment ®sh were cular tanks (2.0 m diameter, 0.8 m depth, 3,140 L transferred to a 3,140-L circular tank (2.0 m di- volume) supplied with seawater (10 L/min, 10± ameter, 0.8 m depth) supplied with seawater (10 520 DAVIS AND PARKER

TABLE 1.ÐMortality in age-1 (small ®sh) and age-2 (large ®sh) sable®sh through 7 d after air exposure (air time) for 10±60 min at 10, 14, and 18ЊC (air temperature). The value for each treatment is the proportion of ®sh that died in a group of six ®sh.

Air temperature (ЊC) Air Small ®sh Large ®sh time (min) 10ЊC14ЊC18ЊC 10ЊC14ЊC18ЊC 10 0 0 0 0 0 0 20 0 0 0 0 0 0 30 0 0 0 0 0 0 40 0.17 0.33 0.67 0.17 0 0 50 0 1 1 0.17 0.33 0.17 60 0.50 1 1 0 0.33 0.67

FIGURE 2.ÐSmall sable®sh had higher mortality com- pared with that of large ®sh after air exposure. Propor- L/min, 7.5±8.5ЊC, 30±32 g/L salinity, O2 Ͼ 90% tion of mortality (1.0 ϭ 100% mortality) was expressed saturation) and held for 7 d. for small and large ®sh exposed to air (10±60 min). Bars Behavior was noted at 1, 2, 3, and 24 h after air are mean Ϯ 1SE(N ϭ 3; calculated from exposure to treatment. Visual observations were made from air at 10, 14 and 18ЊC) for mortality observed after each above the tank for (1) the presence or absence of air exposure time. No mortality was observed at 10, 20, upright orientation in individual ®sh and (2) startle and 30 min in air. responses to a uniform visual stimulus (lifting the tank cover), followed by a uniform mechanical stimulus (striking the side of the tank three times each treatment as described above and used as in- in succession). These behaviors are innate orien- dividual nonreplicated data points in statistical tation and startle responses that are critical for testing. Nonparametric tests were used throughout, swimming and evasion of predators. De®ciencies as data and transformed data did not ®t a standard in these behaviors increase predation on stressed distribution and variances were not homogeneous. ®sh (Olla and Davis 1989; Schreck et al. 1997; Tests were calculated with Statistix 7 software. Ryer et al. 2004). An index for behavior at each Statistical signi®cance was assumed at P equal to observation time in each treatment was calculated 0.050. Effects of ®sh size on mortality and be- by adding the number of ®sh observed to be up- havior index were tested with Wilcoxon's signed right and showing a startle response to visual and rank test by matching measures in corresponding mechanical stimuli. Fish not exposed to stressors treatments among two size-classes. Effects of air always showed full responsiveness (with a total exposure time and air temperature on mortality and score of 6 ϩ 6 ϩ 6 ϭ 18). Scores for individual behavior index were tested with Friedman two- treatments were divided by 18 to calculate the be- way analysis of variance (ANOVA) in two size- havior index as the proportion of full responsive- classes of ®sh separately. Changes in behavior in- ness. Behavioral impairment was de®ned as a de- dex (recovery) between 1, 2, 3, and 24 h after air Downloaded by [Oregon State University] at 17:07 22 August 2011 crease or complete inhibition of normal behavior. exposure were tested with ANOVA in two size- Dead ®sh had no behavior, were removed from the classes of ®sh separately. tank and were not included in the behavior index. If there was mortality in a treatment, then the be- Results havior index was calculated by totaling observed Mortality.ÐMortality was higher in small sa- scores and dividing by the maximum score pos- ble®sh than in large sable®sh (Wilcoxon, P ϭ sible for the number of living ®sh. Mortality as 0.021; Table 1; Figure 2). Mortality was not ob- evidenced by lack of movement and sustained ¯ar- served in small or large ®sh until after 30 min of ing of opercula was noted through 7 d after stressor air exposure. In small ®sh, there was a signi®cant treatment. The proportion of mortality in each rise in mortality between 30 and 50 min (ANOVA; treatment was calculated by dividing the observed Tables 1, 2; Figure 2). In large ®sh, a more gradual mortality by six. increase in mortality was apparent but not signif- Statistical analysis.ÐThe proportion of mortal- icant because of high variability (ANOVA; Tables ity through 7 d and behavior index at 1, 2, 3, and 1, 2; Figure 2). Higher air temperature may have 24 h after stressor treatment was calculated for increased small ®sh mortality (P ϭ 0.061), but SIZE-RELATED DISCARD MORTALITY 521

TABLE 2.ÐEffects of air exposure time (air time) and air temperature on mortality and behavior index in age-1 (small ®sh) and age-2 (large ®sh) sable®sh. Friedman analysis of variance (ANOVA) F-scores with degrees of freedom (Fdf) and probabilities (P) are reported for mortality at 7 d after air exposure and the behavior index 1, 2, 3, and 24 h after air exposure.

Small ®sh Large ®sh Air temperature Air temperature Air time (min) (ЊC) Air time (min) (ЊC)

Item F5 P F2 P F5 P F2 P Mortality 12.4 0.030 5.60 0.061 9.52 0.090 0.20 0.905 Behavior 1h 7.93a 0.048 0.80 0.670 10.9 0.054 1.53 0.466 2h 8.79a 0.032 0.20 0.905 10.0 0.074 2.82 0.244 3h 8.79a 0.032 2.00 0.368 9.78 0.082 2.57 0.277 24 h 3.00a 0.392 2.00 0.368 12.3 0.030 2.92 0.232 a F3.

there was no apparent temperature effect on large Discussion ®sh mortality (ANOVA; Tables 1, 2). Sable®sh orientation and startle behavior was Behavior index.ÐOnly 10 min of air exposure impaired by exposure to air for only 10 min and caused behavioral impairment in sable®sh. Behav- this impairment continued for at least 24 h. Be- ior index for small ®sh decreased as air exposure time increased at 1, 2, and 3 h after exposure havioral impairment was not dependant on ®sh size (ANOVA; Tables 2, 3), while behavior index for for the ®rst 3 h after air exposure, suggesting that large ®sh was related to air time only at 24 h after the effect was produced by a basic change in phys- exposure. Behavior index was lower in small ®sh iology not linked to body size. However, small ®sh than in large ®sh at 24 h after air exposure (Wil- behavior did recover at a slower rate, indicating a coxon, P ϭ 0.002; Figure 3; Table 3). No difference body size effect on recovery. Although the effects was detected among small and large ®sh at1h(P of many environmental factors on behavior have ϭ 0.969),2h(P ϭ 0.929), and 3 h (P ϭ 0.081) been studied, little is known about how air ex- after air exposure. Partial recovery of sable®sh be- posure alters ®sh behavior and its recovery havior (increased behavior index) occurred by 24 (Schreck et al. 1997). In light of the dynamics of

h after air exposure in small (ANOVA; F3 ϭ 25.44, sable®sh behavior recovery, discard mortality P Ͻ 0.001; Figure 3; Table 3) and large ®sh from predation would be expected to be higher in

(ANOVA; F3 ϭ 44.94, P Ͻ 0.001; Figure 3; Table smaller ®sh than in larger ®sh exposed to 10 min 3). Behavior index was not related to increased air of air or more and adds further concern for the temperature in small and large sable®sh (ANOVA; accurate measurement of discard mortality. For Table 2). discarded ®sh in the ocean that are able to sink Downloaded by [Oregon State University] at 17:07 22 August 2011

TABLE 3.ÐBehavior index in age-1 (small ®sh) and age-2 (large ®sh) sable®sh measured 1, 2, 3, and 24 h after exposure to air (air time) for 10±60 min. Data are means ϮSEs (N ϭ 3; calculated from exposure to air at 10, 14, and 18ЊC). When small ®sh were exposed to air for 50 and 60 min, only ®sh at 10ЊC survived and their behavior index was measured. Since behavior could not be measured for small ®sh that died when exposed to air for 50 and 60 min at 14ЊC and 18ЊC, no standard error was calculated (nd).

Air Small ®sh Large ®sh time (min) 1h 2h 3h 24h 1h 2h 3h 24h 10 0.74 (0.13) 0.76 (0.12) 0.78 (0.11) 0.78 (0.11) 0.58 (0.05) 0.63 (0.05) 0.58 (0.02) 1.00 (0.00) 20 0.66 (0.07) 0.58 (0.02) 0.67 (0.07) 0.67 (0.00) 0.39 (0.00) 0.46 (0.02) 0.52 (0.02) 1.00 (0.00) 30 0.33 (0.00) 0.42 (0.02) 0.56 (0.00) 0.67 (0.00) 0.40 (0.04) 0.48 (0.08) 0.50 (0.10) 0.89 (0.11) 40 0.22 (0.11) 0.33 (0.00) 0.41 (0.05) 0.67 (0.00) 0.35 (0.02) 0.45 (0.06) 0.43 (0.07) 0.89 (0.11) 50 0.00 (nd) 0.33 (nd) 0.39 (nd) 0.67 (nd) 0.39 (0.06) 0.41 (0.05) 0.39 (0.06) 0.73 (0.10) 60 0.00 (nd) 0.33 (nd) 0.33 (nd) 0.67 (nd) 0.25 (0.05) 0.36 (0.03) 0.38 (0.03) 0.61 (0.06) 522 DAVIS AND PARKER

(known in Europe as saithe) Pollachius virens (Hoag 1975; Richards et al. 1995; Ross and Hok- enson 1997). Our results con®rm the widely held idea that smaller ®sh are more sensitive to capture stressors than larger ®sh. Small sable®sh mortality appeared and increased abruptly between 30 and 50 min, indicating a threshold-type response. In large ®sh an apparent increase in mortality after 30 min was gradual and variable. Large sable®sh were able to absorb the effects of stress to a greater extent and this ability was also observed in lingcod that were towed in a net and exposed to air (Davis and Olla 2002). Small ®sh were more susceptible to trawl capture and exposure to air than large ®sh for lingcod, Atlantic halibut Hippoglossus hippoglossus, FIGURE 3.ÐPartial recovery of sable®sh behavior oc- and Paci®c halibut, while size effects were also curred in small and large ®sh 24 h after exposure to air. evident in longline discards of Atlantic halibut and Small ®sh had lower behavior index than large ®sh at Atlantic cod Gadus morhua (Neilson et al. 1989; 24 h after air exposure, but no differences were apparent at 1, 2, and 3 h. Bars are mean Ϯ 1 SE for behavior Richards et al. 1995; Milliken et al. 1999; Parker index (small ®sh N ϭ 14, large ®sh N ϭ 18 at all four et al. 2003). Size effects have also been obtained times); data were pooled for small and large ®sh from in ®eld studies of escapees from trawls in haddock all air times and temperatures tested. Melanogrammus aegle®nus, European whiting Merlangius merlangus, vendance Coregonus al- bula, and Atlantic herring Clupea harengus (Su- (no in¯ated gas bladders) but have impaired ori- uronen et al. 1995, 1996a,b; Sangster et al. 1996). entation and startle responses, swimming is often The lack of air temperature effects on sable®sh not possible and they drop rapidly in a catatonic behavior and mortality in this study was not ex- state to the bottom, showing few responses to pred- pected. Previous sable®sh studies showed a ators in the water column and on the bottom. Fish marked increase in mortality when ®sh were ex- with behavioral impairments often have a reduced posed to increased seawater temperature for 30 ability to evade predators (Olla et al. 1995; Ryer min, followed by 15 min in air (Olla et al. 1998; 2002, Ryer et al. 2004). Davis et al. 2001). An explanation of this differ- In contrast to behavioral measures, sable®sh ence may be that the warming of sable®sh is not could be considered relatively resistant to air on as ef®cient in air as it is in seawater and that body the basis of mortality, which did not occur until core temperatures were lower during air exposure after 30 min of air exposure. Other studies in the in the present study. This warming ef®ciency could laboratory have shown that mortality was caused be tested in the laboratory and emphasizes the im- by air exposure ranging from 7 min in walleye portance of measuring body core temperature and Downloaded by [Oregon State University] at 17:07 22 August 2011 pollock Theragra chalcogramma to 45 min in ling- knowing the relationship between body tempera- cod Ophiodon elongatus (Olla et al. 1997; Davis ture, behavioral impairment, and mortality when and Olla 2002). Comparison with past ®eld studies predicting potential discard mortality (Davis and of air exposure in other species is dif®cult because Olla 2001; Davis et al. 2001; Davis 2002). they did not control for ®sh size, temperature, or Studies of discarded ®sh in the laboratory may capture injury. Relative resistance to air exposure be considered arti®cial because all possible stress- after trawl capture was noted in winter ¯ounder ors are not included (e.g., crushing in a net, pres- Pleuronectes americanus and lingcod, which did sure changes, damage from other ®sh and inver- not show measurable mortality until after 45 min tebrates, and hypoxic piles of ®sh). At the same on deck (Ross and Hokenson 1997; Parker et al. time, ®eld studies suffer from a lack of controls 2003). Other discard species were more sensitive and hypothesis testing and are generally conducted to air, with mortality occurring after 15 min in air under a limited set of conditions making gener- for Paci®c halibut Hippoglossus stenolepis, witch alization dif®cult. In this context, the role of lab- ¯ounder Glyptocephalus cynoglossus, American oratory hypothesis testing is to identify the key plaice Hippoglossoides platessoides, and pollock factors that control discard behavior and mortality. SIZE-RELATED DISCARD MORTALITY 523

With this knowledge, we can sample and predict i®cations of ®shing practices could include avoid- discard mortality in the ®eld using a rational model ing areas in which smaller ®sh are abundant and based on the established relationships between reducing trawling times to produce smaller catch ®shing practices, environmental conditions, ®sh per set and shorter handling times. As these meth- biology, and mortality. Measures of discard mor- ods are developed and implemented, the potential tality are key for the management of speci®c ®sh- delayed mortality of discards and escapees from eries. A rational approach to obtaining mortality predation and disease should be estimated. Utiliz- data would include a measurement of (1) discard ing smaller ®sh that are more likely to die from quantity, (2) the proportion of discards that im- capture is a more dif®cult issue and requires the mediately die, and (3) the proportion of discards development of a market and a price structure that showing delayed mortality. Delayed mortality may provides the appropriate incentives for ®shers. A be measured using a condition index based on management and market system that encouraged physical injury, behavior, or physiology. The con- the retention of all sable®sh until the quota was dition index must have a de®ned response curve met would minimize total mortality and ®shing to sublethal stress and mortality and must include effort. However, full retention requirements with- the appropriate range of key factors that are im- out changes in price structure are not enforceable. portant in speci®c ®sheries. While the role of capture injury is obvious, studies have shown that Acknowledgments other key factors which are often ignored in the We thank Michele Ottmar, Mara Spencer, Scott assessment of discard mortality include environ- Haines, Paul Iseri, and Rich Titgen who provided mental variables, ®sh size, behavioral impairment excellent technical assistance during rearing and leading to predation, immune suppression leading the experiment. The protocols used in this research to disease, and factor combinations (Davis 2002). conform to the guidelines for the ethical treatment Mark±recapture studies are useful for developing of experimental animals prescribed by Oregon condition indices if they include an appropriate State University. range of ®shing, environmental, and biological conditions. References The effects of air exposure and ®sh size ob- Ackley, D. R., and J. Heifetz. 2001. Fishing practices served in this study are not expected to impact under maximum retainable bycatch rates in Alaska's ®xed-gear ®sheries which discard ®sh in less than ground®sh ®sheries. Alaska Fishery Research Bul- 10 min, while trawl ®sheries would certainly be letin 8:22±44. Davis, M. W. 2002. Key principles for understanding impacted. It is clear from previous studies that ®sh bycatch discard mortality. Canadian Journal of combinations of stressors during warmer seasons Fisheries and Aquatic Sciences 59:1834±1843. in ®xed-gear ®sheries would increase discard mor- Davis, M. W., and B. L. Olla. 2001. Stress and delayed tality and behavioral impairment (i.e., hooking or mortality induced in Paci®c halibut Hippoglossus trapping followed by increased seawater temper- stenolepis by exposure to hooking, net towing, el- ature and air exposure experienced during ®sh pas- evated sea water temperature and air: implications sage from the bottom to the surface and back to for management of bycatch. North American Jour- nal of Fisheries Management 21:725±732. the bottom; Davis 2002). While sable®sh are ro- Davis, M. W., and B. L. Olla. 2002. Mortality of lingcod Downloaded by [Oregon State University] at 17:07 22 August 2011 bust by some ®sh standards, discard mortality can towed in a net as related to ®sh length, seawater be minimized through changes in ®shing gear and temperature and air exposure: a laboratory bycatch practices and the development of appropriate eco- study. North American Journal of Fisheries Man- nomic incentives. For example, although manda- agement 22:1095±1104. tory in Canada, a growing use of traps equipped Davis, M. W., B. L. Olla, and C. B. Schreck. 2001. Stress induced by hooking, net towing, elevated sea water with escape rings off Alaska and the U.S. West temperature and air in sable®sh: lack of concor- Coast will help to reduce the capture and handling dance between mortality and physiological mea- of smaller sable®sh in the trap ®shery (Department sures of stress. Journal of Fish Biology 58:1±15. of Fisheries and Oceans Canada Paci®c Region Department of Fisheries and Oceans Canada Paci®c Re- 1999; K. Matteson, Oregon Department of Fish gion. 1999. Paci®c region management plan, August and Wildlife, personal communication). Similar 1, 2002±July 31, 2003, Sable®sh. Vancouver. Avail- able: http://www.pac.dfo-mpo.gc.ca/ops/fm/mplans/ escape devices in trawls have not been tested for mplans.htm#Ground®sh (January 2003). sable®sh, where increased mesh size, grates, and FAO (Food and Agriculture Organization of the United other discard reduction devices may help to reduce Nations). 2002. FAO yearbook, ®shery statistics, the quantities landed of smaller ®sh. Other mod- capture production. Volume 90/1, 2000. Rome. 524 DAVIS AND PARKER

Halliday, R. G., and A. T. Pinhorn. 2002. A review of for 2002: stock assessment and ®shery evaluation. the scienti®c and technical bases for policies on the Paci®c Fishery Management Council, Portland, capture of small ®sh in North Atlantic ground®sh Oregon. ®sheries. Fisheries Research 57:211±222. Richards, L. J., J. Fargo, and J. T. Schnute. 1995. Factors Hoag, S. H. 1975. Survival of halibut released after in¯uencing bycatch mortality of trawl-caught Pa- capture by trawls. International Paci®c Halibut ci®c halibut. North American Journal of Fisheries Commission Scienti®c Report 57:1±18. Management 15:266±276. Methot, R. D. 1992. Assessment of the west coast sa- Ross, M. R., and S. R. Hokenson. 1997. Short-term ble®sh stock in 1992. Appendix D in Paci®c Fishery mortality of discarded ®n®sh bycatch in the Gulf of Management Council. Appendices to the status of Maine ®shery for northern shrimp Pandalus bo- the Paci®c coast ground®sh ®shery through 1992 realis. North American Journal of Fisheries Man- and recommended acceptable biological catches for agement 17:902±909. 1993: stock assessment and ®shery evaluation. Pa- Ryer, C. H. 2002. Trawl stress and escapee vulnerability ci®c Fishery Management Council, Portland, to predation in juvenile walleye pollock: Is there an Oregon. unobserved bycatch of behaviorally impaired es- Milliken, H. O., M. Farrington, H. A. Carr, and E. Lent. capees? Marine Ecology Progress Series 232:269± 1999. Survival of Atlantic cod (Gadus morhua)in 279. the Northwest Atlantic longline ®shery. Journal Ma- Ryer, C. H., M. L. Ottmar, and E. A. Sturm. 2004. Be- rine Technology Society 33:19±24. havioral impairment after escape from trawl cod- Neilson, J. D., K. G. Waiwood, and S. J. Smith. 1989. ends may not be limited to fragile ®sh species. Fish- Survival of Atlantic halibut (Hippoglossus hippo- eries Research 66:261±269. glossus) caught by longline and otter trawl gear. Sangster, G. I., K. Lehmann, and M. Breen. 1996. Com- Canadian Journal of Fisheries and Aquatic Sciences mercial ®shing experiments to assess the survival 46:887±897. of haddock and whiting after escape from four sizes Olla, B. L., and M. W. Davis. 1989. The role of learning of diamond mesh cod-ends. Fisheries Research 25: 323±345. and stress in predator avoidance of hatchery-reared Schirripa, M. J., and R. D. Methot. 2001. Status of the coho salmon (Oncorhynchus kisutch) juveniles. sable®sh resource off the U. S. Paci®c coast in 2001. Aquaculture 76:209±214. Appendix in Paci®c Fishery Management Council. Olla, B. L., M. W. Davis, and C. B. Schreck. 1995. Status of the Paci®c coast ground®sh ®shery Stress-induced impairment of predator evasion and through 2001 and recommended biological catches non-predator mortality in Paci®c salmon. Aquacul- for 2002: stock assessment and ®shery evaluation. ture Research 26:393±398. Paci®c Fishery Management Council, Portland, Olla, B. L., M. W. Davis, and C. B. Schreck. 1997. Oregon. Effects of simulated trawling on sable®sh and wall- Schreck, C. B., B. L. Olla, and M. W. Davis. 1997. eye pollock: the role of light intensity, net velocity Behavioral responses to stress. Pages 145±170 in and towing duration. Journal of Fish Biology 50: G. K. Iwama, A. D. Pickering, J. P. Sumpter and C. 1181±1194. B. Schreck, editors. Fish stress and health in aqua- Olla, B. L., M. W. Davis, and C. B. Schreck. 1998. culture. Cambridge University Press, Cambridge, Temperature magni®ed postcapture mortality in U. K. adult sable®sh after simulated trawling. Journal of Suuronen, P., D. L. Erickson, and A. Orrensalo. 1996a. Fish Biology 53:743±751. Mortality of herring escaping from pelagic trawl Parker, S. J., P. S. Rankin, R. W. Hannah, and C. B. codends. Fisheries Research 25:305±321. Schreck. 2003. Discard mortality of trawl-caught Suuronen, P., J. A. Perez-Comas, E. Lehtonen, and V. lingcod in relation to tow duration and time on deck. Tschernij. 1996b. Size-related mortality of herring North American Journal of Fisheries Management (Clupea harengus L.) escaping through a rigid sort- Downloaded by [Oregon State University] at 17:07 22 August 2011 23:530±542. ing grid and trawl codend meshes. ICES Journal of Pinhorn, A. T., and R. G. Halliday. 2001. The regulation Marine Science 53:691±700. of exploitation pattern in North Atlantic ground®sh Suuronen, P., T. Turunen, M. Kiviniemi, and J. Karja- stocks. Fisheries Research 53:25±37. lainen. 1995. Survival of vendace (Coregonus al- PFMC (Paci®c Fishery Management Council). 2002. bula) escaping from a trawl cod end. Canadian Jour- Status of the Paci®c coast ground®sh ®shery nal of Fisheries and Aquatic Sciences 52:2527± through 2001 and recommended biological catches 2533.