Catch Per Effort Research Articles

Effects of Vegetation Removal on Bluegill and Largemouth Bass in Two Minnesota Lakes

Abstract Abundance and growth of bluegill Lepomis macrochirus, diet and growth of largemouth bass Micropterus salmoides, and abundance of age-0 largemouth bass were evaluated in two treatment and three reference lakes in Minnesota to assess the effects of whole-lake herbicide treatments. Lakes were evaluated 1 year prior (1993), during (1994), and after (1995) treatment. In reference lakes, vegetation, fish growth, abundance, and diet remained relatively unchanged throughout the study. Herbicide applications in May 1994 decreased the percentage of sampling stations with vascular vegetation from 100% to 33% in Parkers Lake and 63% in Zumbra Lake between Aug 1993 and 1994. Vegetation returned to some areas of Parkers Lake in 1995 (77%) but continued to decline in Zumbra Lake (43%). Purse-seine catch per effort (CPE) of small bluegill (60–100 mm) decreased following treatment but returned to pretreatment levels the following year, whereas CPE of large bluegill (>100 mm) increased in 1994 in trap nets and rem...

Gill-Net Saturation by Lake Trout in Michigan Waters of Lake Superior

Abstract We conducted experimental fishing for lake trout Salvelinus namaycush in Michigan waters of Lake Superior to determine the importance of soak time on catch per effort (CPE) in numbers per kilometer of standard gill net. We modeled CPE as a nonlinear function of the number of nights between setting and lifting (soak time), in which the nets fill at a certain rate toward some maximum after which the nets cannot hold more fish. We found that lake trout CPE increased with soak time at a rate that varied with lake trout density toward a saturation level that was independent of lake trout density. The CPE values of nets soaked 2–5 nights divided by the CPE of nets soaked 1 night were significantly lower than would be expected had CPE increased as a linear function of the number of nights soaked. We derived a means for correcting gill-net CPE values for differing soak times to a common base of 1 night soaked. We concluded that it is inappropriate to assume lake trout catches in gill nets will increase i...

Estimation of Population Density of Largemouth Bass in Ponds by Using Mark–Recapture and Electrofishing Catch per Effort

Populations of largemouth bass Micropterus salmoides longer than 199 mm total length (TL) in hatchery ponds were estimated by using both mark–recapture and an electrofishing catch-per-effort (CPE) model. and these estimates were compared to actual densities of largemouth bass obtained after draining the pond. Mark–recapture underestimated populations of largemouth bass in 11of 13 ponds. Error in mark–recapture estimation of numbers of largemouth bass decreased as the percentage of the population that was marked increased. Population estimates that used a previously published electrofishing CPE model underestimated population densities of largemouth bass obtained by pond draining, with errors ranging from 62.9 to 89.4%. Electrofishing CPE was significantly (P < 0.05) correlated with population density of largemouth bass but was not correlated with conductivity, turbidity, or plant biomass (P > 0.05 for all). A model to predict density of largemouth bass longer than 199 mm TL in ponds was developed by regressing actual population density against electrofishing CPE.

Comparison of data from voluntary logbook and research catch-sampling programmes in the New Zealand lobster fishery

Since 1993, the New Zealand Fishing Industry Board has run an extensive voluntary programme to collect biological information from rock lobster (Jasus edwardsii) pot fisheries using logbooks maintained by commercial fishers. The New Zealand Ministry of Fisheries has run since 1989 an intensive research sampling programme of the rock lobster commercial fishery which measures nearly every lobster caught in a selected trip. A comparison of these two programmes was made for the southern South Island fishery over a period from August 1993 to January 1996. Length frequency distributions stratified by month and statistical area showed similar distributions from both sampling programmes in most strata, with a tendency for higher frequency modes to be estimated by the voluntary logbook data and larger frequency modes estimated by the research sampling data. These differences were slight except for five instances (of 40 strata compared) where the research sampling programme estimated flat frequency distributions which were not typical of the distributions estimated in other strata. Catch per potlift from the voluntary logbook programme and the compulsory catch per effort landing returns were similar for the same fishers. This indicated that the voluntary fishers were successful in designating ‘representative’ sampling units for their programme.

Causes of Declining Survival of Lake Trout Stocked in U.S. Waters of Lake Superior in 1963–1986

Survival of the 1963–1982 year-classes of stocked yearling lake trout Salvelinus namaycush declined significantly over time in Lake Superior. To investigate possible causes of this decline, a Ricker model of stock–recruitment was used to describe the catch per effort (CPE) of age-7 stocked lake trout in the Michigan, Minnesota, and Wisconsin waters of Lake Superior as functions of the numbers of yearlings stocked 6 years earlier (an index of density dependence), the density (CPE) of wild adult lake trout (an index of predation), and large-mesh (≥114-mm stretch-measure) gill-net fishing effort (an index of fishing mortality). Declining CPE of stocked lake trout in Michigan and Wisconsin was significantly associated with increasing large-mesh gill-net fishing effort. Declining CPE of stocked lake trout in Minnesota was significantly associated with increasing density of wild lake trout. Declining survival of stocked lake trout may therefore have been caused by increased mortality in large-mesh gill-net fisheries in Michigan and Wisconsin, and by predation by wild lake trout that recently recolonized the Minnesota area. We recommend that experimental management be pursued to determine the relative importance of large-mesh gill-net fishing effort and of predation by wild lake trout on the survival of stocked lake trout in U.S. waters of Lake Superior.

Seasonal Variation in Gill-Net Sample Indexes for Northern Pike Collected from a Glacial Prairie Lake

We captured 702 northern pike Esox lucius in 416 gill-net sets on 17 monthly occasions from July 1991 to June 1993 to examine seasonal variation in sampling data in Lake Thompson, South Dakota. Mean catch per effort (CPE) of northern pike 35 cm or longer differed significantly among months during both years. Mean CPE was lowest in winter and peaked in spring of both years. Size structure estimates were lowest during early spring and summer when males dominated samples and were highest during winter when females dominated samples. Northern pike 86 cm or longer were caught primarily in winter during ice cover. Relative weight (Wr) of male and female northern pike increased during fall, peaked in late winter, and declined during the spawning period. A similar pattern was found for the gonadosomatic index of female northern pike but not for males. Increases in the gonadosomatic index for males occurred entirely during fall. Gonadosomatic index and Wr were positively correlated for female northern pike, but the correlation was lower for males. We suspect our findings will be most applicable for interpreting northern pike population surveys made during narrow time periods near the southern portion of the speciesˈ range and for populations found in shallow, warmer water bodies.

Comparison of Catch per Effort and Removal Procedures for Sampling Stream Fish Assemblages

Abstract Methods used to estimate fish abundance in streams should be chosen based on the precision required by the study, the available time, and the number and kinds of species targeted. When entire assemblages of predominantly small, nongame fishes are to be sampled, most existing procedures have limitations. We compared estimates of species richness, abundance, and assemblage structure based on catch per effort (CPE) during a single tow-barge electrofishing sample versus intensive tow-bare electrofishing removal sampling procedures with block nets in paired, contiguous stations on nine streams in southern Wisconsin. Use of block nets had little effect on CPE during single upstream electrofishing passes; for stations approximately 35 times the mean stream width in length, the overall influence of fish entering and leaving the station appeared to be negligible. Estimates of abundance, based on total catch and based on the removal model, were higher in removal stations than in CPE stations. However, esti...

Declining Survival of Lake Trout Stocked during 1963–1986 in U.S. Waters of Lake Superior

Abstract The average catch per effort (CPE) values for the 1963–1982 year-classes of stocked lake trout Salvelinus namaycush caught at age 7 in gill nets and for the 1976–1986 year-classes caught at ages 2–4 in trawls declined significantly in U.S. waters of Lake Superior. The declines in CPE were not explained by reduced stocking, but rather by significant declines in survival indices of the year-classes of stocked lake trout. Increases in mortality occurred in year-classes before the fish reached ages 2–4, before they were recruited into the sport and commercial fisheries, and before they reached sizes vulnerable to sea lamprey predation. We conclude that declining abundance of stocked lake trout resulted from increased mortality, which may have been caused by competition, predation, or by a combination of these and other factors. Restoration of lake trout in Lake Superior may now depend on prudent management of naturally reproducing stocks rather than on stocking of hatchery-reared fish.

Management Briefs: Predicting Population Density of Largemouth Bass from Electrofishing Catch per Effort

Population density (D, number/hectare) of largemouth bass Micropterus salmoides was related to electrofishing catch per effort (CPE) for a Wisconsin lake. A similar relation that was previously described for 12 Ohio lakes was verified with the Wisconsin data, and the data were combined to yield the following regression equation (r = 0.89): log10 D = 1.1641 log10CPE − 0.45161.

Effects of Winter Temperature and Predation on the Abundance of Alewife ( Alosa pseudoharengus) in the Bay of Quinte, Lake Ontario

Alewife ( Alosa pseudoharengus) abundance in the Bay of Quinte, Lake Ontario, was monitored with a bottom trawl survey from 1972 to 1987. Prior to 1977, alewife catch-per-effort (CPE) was high in all areas of the bay but declined drastically following unusually cold winters in 1976–77 and 1977–78. Beginning in 1980, alewife CPE recovered in the lower bay, adjacent to Lake Ontario. This recovery was not observed in the upper bay where predation by a resurgent walleye ( Stizostedion vitreum) population maintained the reduced numbers of alewife. We conclude that walleye predation has played an important role in generating differences in alewife abundance between the upper and lower bays since 1980. There is a negative correlation between adult alewife CPE and young-of-year (YOY) alewife CPE suggesting that intraspecific predation is an important factor in the production of YOY alewife in the Bay of Quinte. Recruitment mechanisms for alewife in the Bay of Quinte may depend more on intraspecific predation, in contrast to Lake Ontario where intraspecific competition for zooplankton has been hypothesized as a limiting factor.