Small-mesh Gillnets Research Articles

Some warning signs detected in coastal pelagic fisheries of the west coast of Sri Lanka: Declining trend of <em>Amblygaster sirm</em> suggesting the need for immediate management initiatives

Coastal fisheries, mainly characterized by small pelagic species, are significant on the west coast of Sri Lanka in terms of livelihood and food security. However, currently, the fishery has faced numerous challenges, particularly with the stock depletion allied with poor management practices. The present study was carried out using the time series data of 2001–2020 on the west coast of Sri Lanka representing four fisheries districts - Kalutara, Colombo, Negombo, and Chilaw - to explore the present status and the tendency of the fishery towards management considerations. The analysis was based on the outboard engine fiber-reinforced plastic boats (OFRP) with small meshed gillnets, which are the main boat gear combination that exists in the fishery. The recent five-year landings within the study period indicated that the highest average catch rates resulted in the onset of the southwest monsoon and extended until the end of the northeast monsoon. The catch rates of fishery exhibited greater inter-annual fluctuations during a two-decade period, with an average of 66.7 ± 17.3 kg per trip from 2011 to 2020. Over the past two decades, the Mean Trophic Level (MTL) of the coastal fish landings ranged from 3.13 to 3.62 and showed a declining trend with the forecast of 3.38 for 2022-2026. Moreover, the catch rates and the relative contribution of Amblygaster sirm, one of the main target species in the country, showed a declining trend over the past two decades while indicating the need for immediate management initiatives.

Simulating Mesh-size and Selection Pattern Impacts on the Lake Turkana Fisheries Sustainability in Kenya

The study compared impacts of different gear mesh sizes and landing sizes (Lcap) through gillnet and knife-edge selection patterns on Tilapia and Nile perch of Lake Turkana. The results will help contribute to the debate on whether to capture large and protect small fish or vice versa. R simulation employing the 1934 Thompson and Bell's model for data-deficient stocks was used to simulate fish cohorts using secondary input data for the two species. Gillnet selection pattern with recommended mesh size (127 mm) produced an 80% increase in Tilapia YPR while ESS and SPR ratios reduced by 12.5%. and 14.3% respectively when fishing mortality (F) was tripled to 3.0. Nile perch's YPR increased by 90% while ESS and SPR dropped by 70 and 75% each when F increased to 0.8. Tilapia YPR maximized by reducing mesh size to 101.6 mm at F=2, and maintained ESS and SPR at 20% each, while the Nile perch YPR dropped by 20% and 66.7% respectively at F=1.0. Small mesh-sized (<40 mm) gears had no effect on Tilapia’s ESS and SPR but produced the lowest YPR ratios. The 152.4 mm mesh for Nile perch produced a 25% YPR increase and maintained optimal ESS and SPR at F=0.5. Knife-edge selection pattern utilizing 127 mm, 20 cm Lcap and F=1.5, produced 50% YPR, ESS, and SPR for Tilapia, and maintained at F=3.0. Large-sized Nile perch using 152.4 mm gear resulted in about 40% YPR of the stock. Reduction of Lcap using 127 mm gear, produced a 75% increase in YPR. ESS and SPR depicted Nile perch collapse at F>0.65. Mesh size and selection pattern impacts are dependent on F. Small mesh gillnets are not damaging if F is controlled and caution should be taken with them in a knife-edge selection. This study recommends 101.6 mm and 152.4 mm mesh sizes for Tilapia and Nile perch respectively in Lake Turkana

Gillnetting for small indigenous cyprinids in a Sri Lankan reservoir where culture-based fisheries are practiced

In Sri Lankan reservoirs, small, indigenous fish species (SIS) are abundant and can be differentially exploited using small mesh (15-38 mm stretched mesh sizes) gillnets without any detrimental effects on the cichlid fisheries. However, in the recent past a paradigm shift in the reservoir fisheries of Sri Lanka is observed from total dependence on exotic cichlids to exploitation of exotic carps, stocked in reservoirs for the development of culture-based fisheries (CBF). As fingerlings of Chinese and Indian major carps and common carp are regularly stocked in reservoirs for the development of CBF, it is essential to investigate the potential impact of the use of small mesh gillnets to catch SIS on stocked fish fingerlings on CBF. In the present study, small mesh gillnets were used to exploit SIS during September 2011 to March 2013 when carp fingerlings were stocked in Chandrika wewa, Sri Lanka. The results revealed that no carp fingerlings (except 2 specimens of Indian carp species) were caught in any of the fishing trials with small mesh gillnets. As juvenile fish and stocked fish fingerlings occur in shallow littoral areas of reservoir, and as small mesh gillnets are laid at the depths ≥ 1.5 m, there is a habitat segregation of these two categories of fish. It is therefore possible to introduce a subsidiary fishery with small mesh gillnets to exploit SIS, which can co-exist with CBF in reservoirs of Sri Lanka.

Ecological change alters the evolutionary response to harvest in a freshwater fish.

Harvesting can induce rapid evolution in animal populations, yet the role of ecological change in buffering or enhancing that response is poorly understood. Here, we developed an eco-genetic model to examine how ecological changes brought about by two notorious invasive species, zebra and quagga mussels, influence harvest-induced evolution and resilience in a freshwater fish. Our study focused on lake whitefish (Coregonus clupeaformis) in the Laurentian Great Lakes, where the species supports valuable commercial and subsistence fisheries, and where the invasion of dreissenid (zebra and quagga) mussels caused drastic shifts in ecosystem productivity. Using our model system, we predicted faster rates of evolution of maturation reaction norms in lake whitefish under pre-invasion ecosystem conditions when growth and recruitment of young to the population were high. Slower growth rates that occurred under post-invasion conditions delayed when fish became vulnerable to the fishery, thus decreasing selection pressure and lessening the evolutionary response to harvest. Fishing with gill nets and traps nets generally selected for early maturation at small sizes, except when fishing at low levels with small mesh gill nets under pre-invasion conditions; in this latter case, evolution of delayed maturation was predicted. Overall, the invasion of dreissenid mussels lessened the evolutionary response to harvest, while also reducing the productivity and commercial yield potential of the stock. These results demonstrate how ecological conditions shape evolutionary outcomes and how invasive species can have a direct effect on evolutionary responses to harvest and sustainability.

Size-selective fishing and the potential for fisheries-induced evolution in lake whitefish.

The long‐term evolutionary effects of fishing on maturation schedules can depend on gear type, the shape of the gear type's size‐selectivity function, and the size and age structure of a population. Our goal was to better understand how environmentally induced differences in somatic growth influence the evolutionary effects of size‐selective fisheries, using lake whitefish (Coregonus clupeaformis) in Lake Huron as a case study. Using a state‐dependent optimization model of energy allocation parameterized for lake whitefish, we show that fishing with gill nets (bell‐shaped selectivity) and trap nets (sigmoid‐shaped selectivity) can be potent agents of selection on size thresholds for maturity. Compared to trap nets and large mesh (114 mm) gill nets, small mesh (89 mm) gill nets are better able to buffer populations from fishing‐induced evolution by safeguarding large, fecund fish, but only when overall fishing mortality is low and growth rates sufficiently fast such that fish can outgrow vulnerable size classes. Regardless of gear type, and all else being equal, high fishing mortality in combination with low growth rates is expected to intensify the long‐term evolutionary effects of fishing.

A 10-year comparison of the Pohnpei, Micronesia, commercial inshore fishery reveals an increasingly unsustainable fishery

In Pohnpei, Micronesia, a 10-year (2006–2015) follow-up market survey was conducted to provide the basis for a comparative assessment of the status of the commercial inshore fishery, to inform management and to identify the most relevant management options. Within this timeframe, marketed coral reef fish volumes declined by 50 mt (ca. 20%), the use of unsustainable fishing methods (nighttime spearfishing and small-mesh gillnets) increased from 75.5% to 81.9%, and catch-per-unit-effort decreased from 3.4 ± 0.1 to 3.2 ± 0.4 kg h−1 fisher1. Simultaneously, the economic return as price per unit effort was nearly halved for all gear types. Trip volumes increased, however, this was paralleled by a rise in the average number of fishers per trip, particularly for nighttime spearfishing. Effort shifted from inner to outer reef areas and further away from high fisher density communities. At the family level, increases in the percentage of lower tropic level catch were observed, with herbivores and planktivores increasing in frequency in catch more than other trophic level fishes. The only weight increase among top carnivores was for epinephelids, however this was accompanied by a greater contribution by juveniles for the most commonly targeted grouper, Camouflage grouper, Epinephelus polyphekadion. Among fish families, eight epinephelids were absent in catch in 2015 compared to 2006, with additional species observed in speared catch in 2015 that were absent in 2006. To reverse continuing declines and prevent the potential for fisheries collapse, government needs to institute rights-based management, ban the use of nighttime spearfishing and small-mesh gillnets, and improve existing enforcement within marine protected areas and markets.

Assessing sea turtle bycatch in Northeast Brazil through an ethnozoological approach

Bycatch in artisanal fisheries poses a significant threat to sea turtles populations globally, evidencing need for studies aimed at analyzing the impact of bycatch of sea turtles and their conservation. Considering the decentralized nature of artisanal fisheries, limited infrastructure for research and monitoring, collecting data on bycatch through interviews is recognized as an alternative method for estimating the magnitude of bycatch in artisanal fisheries. Using an ethnozoological approach, this work aimed to obtain data on the bycatch of sea turtles along the coast of the state of Paraíba (Northeast Brazil). The study focused on the following hypotheses: 1) the bycatch of sea turtles on the Paraíba coast is associated with different fishing techniques, and gillnets have the most impact on the animals; and 2) large-mesh gillnets that have higher bycatch than small-mesh gillnets. The results revealed that bycatch caused by gillnets was significantly greater in comparison with other fishing gear. Gillnets with a mesh size of more than 50 mm caused more bycatch of sea turtles than one with a smaller mesh size. Recommendations to reduce bycatch and mortality of sea turtles are proposed.

Assessment of efficiency and impacts of gillnets on fish conservation in a tropical freshwater fishery

Abstract Gillnets are commonly used in tropical multi‐species fisheries and there is a need to investigate the comparative efficiency and impacts of this gear on fish populations and diversity. The efficiency and the impact of gillnets of distinct mesh sizes were compared in the Lower Tocantins River (Brazilian Amazon). Fish sampling was conducted in 12 floodplain lakes using gillnets of distinct mesh sizes and 345 fish landings were recorded. Indicators of gillnet efficiency were: (1) catch per unit of effort (CPUE) of total fish sampled; (2) CPUE of fish caught by fishers; (3) CPUE of commercial fish sampled; and (4) proportion of biomass of commercial fish sampled. Indicators of impact were: (1) the number of non‐commercial fish (by‐catch); (2) the proportion of fish above the length at first maturity; (3) mean fish size (length); (4) total number of fish species and of rare fish species caught. Gillnets of 8 cm mesh size showed a higher CPUE in fish samples and fish landings. This mesh size also showed reduced impacts (lower numbers of non‐commercial fish caught and higher proportion of adult fish). Gillnets of 6 cm mesh size caught a smaller proportion of adult fish, smaller fish, more species and more rare species. Therefore, intensive use of these gillnets could increase the risk of regional species extinctions and impair the provision of ecosystem services by target fish. Gillnets of 8 cm mesh size could improve fish catches while minimizing adverse effects of gillnet fishing. The practical management recommendation would be to replace the more damaging small mesh gillnets by gillnets with intermediate mesh size. This recommendation could simultaneously protect small‐sized rare species and larger fish, being broadly applicable to other small‐scale and multi‐species fisheries that use gillnets intensively in tropical countries with high fish diversity. Copyright © 2016 John Wiley & Sons, Ltd.

Implications of using small meshed gillnets for the sustainability of fish populations: a theoretical exploration based on three case studies

AbstractThe study explores the impacts of varying gillnet mesh size and fishing level on yield per recruit (Y/R), escapement spawning stock (ESS) and mega‐spawners (MS) of three widely distributed freshwater fishery target species. Y/R is maximised when the optimal length of capture (Lcap) is above the size of maturity (L50). However, the unimodal shape of gillnet selectivity results in lower impacts to ESS and MS with both smaller and larger mesh sizes. Under conditions of moderate exploitation, the fraction of MS was significantly larger if small meshed gillnets were used. This is due to the relatively smaller cumulative vulnerability from small mesh sizes through time, as they target a smaller size range of fish, which also grow more quickly through the vulnerable window due to higher growth rates. Therefore, unlike trawls and beach seines, which select all size classes beyond the minimum length of capture (Lc), small meshed gillnets are not necessarily destructive and may rather promote sustained production by allowing a higher proportion of the spawning biomass to remain in the stock. The work also helps to explain the observation of sustained fish production in many developing countries despite the persistent use of gillnets of small mesh size that target small, under‐sized individuals.

Impact of women involvement in fisheries on socio-economics of fisher households in Negombo, Sri Lanka

The socio-economics of the households in Wellaweediya fishing village in Negombo, Sri Lanka were studied in relation to women involvement in fisheries. No women in the village were engaged in pre-harvest activities and catching fish. Of the women involved in fisheries, about 50% were involved in fish processing activities such as gutting, salting and sun-drying. Those who were involved in gutting of fish earned about Rs. 300.00 for working for 6 hours per day while those who were engaged in salting and sun-drying were paid only Rs. 200.00 for working for about 12 hours per day. About 31% were involved in marketing the catch. By working for about 3½ hours per day, they earned Rs. 200.00 - 700.00. About 13% were involved in removing fish from small meshed gill nets and they were paid about Rs. 100.00 for working for 2 hours per day. The balance 6% were involved in collecting fish in to transportation baskets and for working for about 2 hours they were paid Rs. 100.00 if the catch was good and Rs. 50.00 if the catch was poor. The women labour of those involved in salting and drying and collecting fish into transportation baskets were found to be exploited with gender discrimination. The mean monthly income of the households where women were involved in fisheries was about Rs. 9350.00, which was about twice of the income of the households where women were not involved in fisheries. Most of the women involved in fisheries could not write and/or read and spent a more traditional way of life. Husbands of most of them were regular consumers of liquor. These women have not changed their gender based household division of labour and carried out activities such as cooking, washing, taking care of children etc. DOI: 10.4038/sljas.v14i0.2199 Sri Lanka J. Aquat. Sci. 14 (2009): 45-57

Gillnet Selectivity of Small Cyprinids in Three Sri Lankan Reservoirs

As it has been reported that there is a harvestable potential of presently unexploited small cyprinid species in Sri Lankan reservoirs, attempts were made to investigate the gillnet selectivity for small cyprinids in three reservoirs with a view to defining regulatory measures for the subsidiary gillnet fishery. As exotic cichlids support profitable fisheries in reservoirs of Sri Lanka, any strategy to exploit small cyprinids should not adversely affect the cichlid stocks. Possibly due to the depth preference, exotic cichlids are not caught in small mesh (12.5 to 37 mm) gillnets which are set in the areas with water depths of over 2 m. The effective mesh sizes (stretched) of gillnet which were set in these areas were 16 and 20 mm for Amblypharyngodon melettinus and 33 and 37 mm for Puntius chola and P. filamentosus. Although P. dorsalis is caught in significant numbers in 50 and 60 mm mesh gillnets, this species is unlikely to be exploited without harming exotic cichlids because sub-adults of exotic cichlids are also caught in these mesh sizes. The importance of gillnet selectivity studies of small indigenous cyprinids in Sri Lankan reservoirs is discussed. * Corresponding author. Tel.: +94 11 2903 397, Fax. +94 11 2914 479 E-mail address: zoousa@kln.ac.lk Asian Fisheries Science 22(2009):885-900 886

Habitat utilization of juvenile lake sturgeon,Acipenser fulvescens, in a large Canadian river

An increased understanding of the juvenile life history stage of the lake sturgeon, Acipenser fulvescens, has been recognized as a key requirement for improving conservation efforts for this once abundant species. The objectives of the current study were to develop an effective methodology for capturing juvenile lake sturgeon in a large riverine environment; to describe the physical habitat characteristics (depth, water velocity and substrate) associated with the areas where juvenile lake sturgeon were captured; and to determine basic population parameters (length, body mass and condition factor) for juvenile lake sturgeon captured in those areas. Gillnets (mesh sizes 25–108 mm) were used to sample the Winnipeg River, a large river in the northern extent of the species range, from 12 June to 6 November 2006. A total of 2154 juvenile (<530 mm FL) lake sturgeon were captured, which represented over 74% of the total fish catch. Moderate (51–108 mm) and small (25 mm) mesh gill nets were found to be efficient for sampling juvenile lake sturgeon, with the former capturing a wider range of sizes and the latter capturing fewer fish but resulting in decreased mortality. Juvenile lake sturgeon were captured at high densities in discrete areas characterized by water depths >13.7 m, detectable water velocities >0.20 m s−1, and various substrate types.

Observations on the age and growth of Varicorhinus damascinus (Val.) in Tigris river at Salahuldin province – Iraq

Age and growth of Varicorhinus damascinus (Val.) in Tigris river at Salahuldin province have been investigated. Monthly samples were taken during the period from September 1999 to August 2000, using small-meshed gill nets. The age data showed that there were six age groups and the dominant age groups were (III – IV) for both sexes. The results of the present study revealed that the increment in length of V. damascinus at the sites of study showed a tendency to decrease with the increase in age, after the third year of life in both sexes. The length-weight relationship of males and females were calculated and demonstrated in a straight line logarithmic formula, as follows: Log W = 1.5404 + 2.6885 log L for males r = 0.95 (P &gt; 0.05) Log W = 1.6723 + 2.7877 log L for females r = 0.77 (P &gt; 0.05) The values of the regression coefficient (b) indicated that the growth of both sexes of V. damascinus was allometric..

Observations on the age and growth of Varicorhinus damascinus (Val.) in Tigris river at Salahuldin province – Iraq

Age and growth of Varicorhinus damascinus (Val.) in Tigris river at Salahuldin province have been investigated. Monthly samples were taken during the period from September 1999 to August 2000, using small-meshed gill nets. The age data showed that there were six age groups and the dominant age groups were (III – IV) for both sexes. The results of the present study revealed that the increment in length of V. damascinus at the sites of study showed a tendency to decrease with the increase in age, after the third year of life in both sexes. The length-weight relationship of males and females were calculated and demonstrated in a straight line logarithmic formula, as follows: Log W = 1.5404 + 2.6885 log L for males r = 0.95 (P &gt; 0.05) Log W = 1.6723 + 2.7877 log L for females r = 0.77 (P &gt; 0.05) The values of the regression coefficient (b) indicated that the growth of both sexes of V. damascinus was allometric..

Trophic interactions in the coastal ecosystem of Sri Lanka: An ECOPATH preliminary approach

This study attempts to assemble and summarize existing information in order to build a general representation of the trophic interactions within the shallow coastal ecosystem of Sri Lanka. A multispecific ecosystem-based approach on trophic relationships and their possible variations was performed using ECOPATH. Thirty-nine functional groups were considered representing all trophic levels in the food web. Time-dynamic simulation was carried out using the ECOSIM routine to evaluate the impact of the 1998 El Niño event on key functional groups. Results show that the time needed for any impacted functional group to recover to its initial abundance increased with the trophic level. Two time-series data sets derived from commercial catch and effort statistics were used for validation of ECOSIM results. The El Niño simulation results validated by the time-series data confirmed the ability of the proposed multispecies model to describe the sudden environmental changes. Possible impacts due to increase of fishing effort were also simulated by separately considering frequently used fishing gears. The analysis revealed that small-mesh gillnet fishery operates independently from the other existing developing fisheries in the same area and can be managed accordingly. Fishing-effort simulations suggest that the increase of fishing intensity by small-mesh gillnets would contribute to the decline of small pelagic catch. This was also found to influence the overall catch. The present level of exploitation of small pelagic fishery resources does not seem sustainable.

Development of an assessment approach for remnant lake salmonin populations: The Crean Lake example

This research investigates a status assessment approach for remnant lake salmonin populations, using the lake charr (Salvelinus namaycush Walbaum) of Crean Lake (105 km 2 ) as an example. A mark-recapture program was implemented employing small-mesh gill nets to ensnare charr by the teeth at spawning. Prior to sampling, potential spawning sites were designated primary or secondary based on habitat. Most charr were caught on three primary reefs, with some spawners moving between reefs. The spawning period peaked at day 2, enhancing spawning synchrony, and lasted up to 10 days. Results produced very low sampling mortality (5.7%), consistent estimates of the number of spawning charr (∼60 y −1 )a nd av ery low (<2000) estimate of the total number of mature charr in Crean Lake. The approach offers an effective means of assessing remnant salmonins with minimal impact on their populations.

Survival of spring chinook salmon captured and released in a selective commercial fishery using gill nets and tangle nets

We tested the potential for using live capture, selective harvest as an alternative to a conventional gill net fishery to protect depressed wild stocks of spring chinook salmon (Oncorhynchus tschawytscha) while still allowing harvest of fish from abundant stocks. We conclude that using modified fish handling techniques and replacing conventional 8 or 5.5 in. gill nets with smaller meshed tangle nets significantly improves the survival of spring chinook salmon released from the gear. Tangle nets are similar to small meshed gill nets and capture fish by the snout rather than by the gills or body, reducing injury and allowing them to continue respiring while they are in the net, theoretically allowing live capture and improving the likelihood of survival after release. Experienced gill netters used modified fishing techniques to fish nets constructed of tangle nets joined to conventional gill nets. Captured fish from each net type were tagged and released for recovery in subsequent recreational and commercial fisheries, at hatchery racks, and during spawning ground surveys. Control fish that had not been captured in the fishing gears were tagged and released from a trap near the fishing area. More than 95% of the adult chinook salmon survived the initial capture in any net type. Spring chinook released from the 4.5 in. tangle net were recovered at 1.9 times the rate of fish released from the 8 in. gill net, and 1.2 times the rate of fish released from the 5.5 in. gill net. The 4.5 in. tangle net was as effective at capturing spring chinook as the 8 in. gill net, but less effective than the 5.5 in. gill net.

Survival of spring chinook salmon captured and released in a selective commercial fishery using gill nets and tangle nets

We tested the potential for using live capture, selective harvest as an alternative to a conventional gill net fishery to protect depressed wild stocks of spring chinook salmon ( Oncorhynchus tschawytscha ) while still allowing harvest of fish from abundant stocks. We conclude that using modified fish handling techniques and replacing conventional 8 or 5.5 in. gill nets with smaller meshed tangle nets significantly improves the survival of spring chinook salmon released from the gear. Tangle nets are similar to small meshed gill nets and capture fish by the snout rather than by the gills or body, reducing injury and allowing them to continue respiring while they are in the net, theoretically allowing live capture and improving the likelihood of survival after release. Experienced gill netters used modified fishing techniques to fish nets constructed of tangle nets joined to conventional gill nets. Captured fish from each net type were tagged and released for recovery in subsequent recreational and commercial fisheries, at hatchery racks, and during spawning ground surveys. Control fish that had not been captured in the fishing gears were tagged and released from a trap near the fishing area. More than 95% of the adult chinook salmon survived the initial capture in any net type. Spring chinook released from the 4.5 in. tangle net were recovered at 1.9 times the rate of fish released from the 8 in. gill net, and 1.2 times the rate of fish released from the 5.5 in. gill net. The 4.5 in. tangle net was as effective at capturing spring chinook as the 8 in. gill net, but less effective than the 5.5 in. gill net.

Growth of Atlantic Salmon parr in fluvial and lacustrine habits

The growth of naturally recruited Atlantic salmonSalmo salarparr in fluvial and lacustrine habitats was investigated in three northern Norwegian watercourses. Salmon parr were sampled in autumn with small mesh gillnets in lakes, and by electrofishing in streams. In three northern Norwegian watercourses, lacustrine Atlantic salmonSalmo salarparr were larger in length and weight at age than fluvial parr. Back‐calculated lengths indicated that lacustrine salmon parr were recruited from the fastest growing part of the populations and they had larger growth (length) increments between age intervals than fluvial parr. There was no consistent pattern in growth comparisons between parr from the inlet and outlet streams. Temperature regime alone could not explain the growth difference observed between parr from the different habitats.

Relative Abundance of Lake Trout and Burbot in the Main Basin of Lake Michigan in the Early 1930s

We used general linear models to compare and to assess the sources of variation in CPUEs (catches per unit effort) of lake trout Salvelinus namaycush and burbot Lota lota netted in small-mesh gill nets from the main basin of Lake Michigan in the early 1930s, before populations of both species collapsed. Spring, summer, and fall CPUEs were modeled separately. In all seasons combined, CPUEs were over 2.5 times greater for lake trout than for burbot, and lake trout CPUEs were greater than burbot CPUEs in five of six regions of the lake. The hypothesized sources of variability in loge(CPUE) included lake region, depth (either as a linear [depth only] or a quadratic [depth and depth2 included] relationship), number of nights out that the nets fished (also as either a linear or quadratic relationship), and the possibility that the effects of depth could vary among regions. The models predicted 57–68% of the variation in lake trout CPUE and 29–37% of the variation in burbot CPUE (log scales). Lake region was highly significant for both species in all seasons. In all seasons, the relationship between lake trout loge(CPUE) and depth was quadratic and varied among regions. For lake trout we did not find any effects of number of nights out. Burbot loge(CPUE) varied linearly with depth and with nights out in the spring. In the summer, loge(CPUE) for burbot varied linearly with nights out, and its relationship with depth was quadratic and varied among regions. In the fall, quadratic relationships between burbot loge(CPUE) and depth again differed among regions, but there was no relationship with nights out.