Maximum Catch Research Articles

Use of generalized linear models in analyzing the catch and effort data on the western king prawn Penaeus latisulcatus Kishinouye in the Gulf St. Vincent, Australia

Abstract The western king prawn Penaeus latisulcatus occurs in coastal waters off Western Australia, the Northern Territory, Queensland, New South Wales, and South Australia. In South Australia, it supports a commercial trawl fishery with an annual landed value of about AU$ 35 million. In this paper, I derive generalized linear models from an observational model of a sex-, age- and time-dependent model for a single prawn population, provide them with a firm theoretical basis, and make explicit some of their assumptions. Following an exploratory analysis by use of a generalized additive model, I use generalized linear models to analyze the commercial catch and effort data for the changes in its stock size with time, in fishing efficiency among vessels, in catch with time of day, fishing effort and area, and the effects of searching on catch. The results obtained by assuming that the catch follows independent log-gamma, log-normal, log-negative binomial, or log-Poisson distribution were similar. The relative exploitable biomass in the population immediately before the fishery was closed in 1991 was 31% of that when it was resumed in December 1993, remained at about the same level of December 1993 until 30 June 1995, slightly declined from 1 July 1995 to 30 June 1997, and was 81% of the level of December 1993 from 1 January 1998 onward. The relative instantaneous rate of fishing mortality of prawns of a particular sex and age was largely unchanged, but became less variable with time. Fishing efficiency was similar among all vessels. Normal fishing shots (using three nets) produced about three times the catch of searching shots (using only one net). Fishers learned during a sequence of shots, for prawn catch initially increased with shot number and then leveled off. A significant variation in catch with the time of day was detected, with the maximum catch occurring at 22 h. Finally, catch did not change proportionally with fishing effort; a 1% of change in effort led only to a nearly 0.9% of change in catch, so that raw catch per unit of effort decreased with fishing effort and is a biased index of the size of a prawn population. This work suggests that the current level of fishing effort cannot sustain the exploitable biomass of the population at the level of December 1993.

Use of generalized linear models in analyzing the catch and effort data on the western king prawn Penaeus latisulcatus Kishinouye in the Gulf St. Vincent, Australia

The western king prawn Penaeus latisulcatus occurs in coastal waters off Western Australia, the Northern Territory, Queensland, New South Wales, and South Australia. In South Australia, it supports a commercial trawl fishery with an annual landed value of about AU$ 35 million. In this paper, I derive generalized linear models from an observational model of a sex-, age- and time-dependent model for a single prawn population, provide them with a firm theoretical basis, and make explicit some of their assumptions. Following an exploratory analysis by use of a generalized additive model, I use generalized linear models to analyze the commercial catch and effort data for the changes in its stock size with time, in fishing efficiency among vessels, in catch with time of day, fishing effort and area, and the effects of searching on catch. The results obtained by assuming that the catch follows independent log-gamma, log-normal, log-negative binomial, or log-Poisson distribution were similar. The relative exploitable biomass in the population immediately before the fishery was closed in 1991 was 31% of that when it was resumed in December 1993, remained at about the same level of December 1993 until 30 June 1995, slightly declined from 1 July 1995 to 30 June 1997, and was 81% of the level of December 1993 from 1 January 1998 onward. The relative instantaneous rate of fishing mortality of prawns of a particular sex and age was largely unchanged, but became less variable with time. Fishing efficiency was similar among all vessels. Normal fishing shots (using three nets) produced about three times the catch of searching shots (using only one net). Fishers learned during a sequence of shots, for prawn catch initially increased with shot number and then leveled off. A significant variation in catch with the time of day was detected, with the maximum catch occurring at 22 h. Finally, catch did not change proportionally with fishing effort; a 1% of change in effort led only to a nearly 0.9% of change in catch, so that raw catch per unit of effort decreased with fishing effort and is a biased index of the size of a prawn population. This work suggests that the current level of fishing effort cannot sustain the exploitable biomass of the population at the level of December 1993.

Model Comparisons for Estimating the Relationship between Catch and Soak Time for the American Lobster Trap Fishery

Abstract The relationship between catch and soak time in the fishery for American lobster Homarus americanus in the northwest Atlantic region was examined by comparing two three-parameter models. The fit of the two models to nine data sets was fairly similar, but a clearer interpretation of model parameters related to rates of entry and escape and an opportunity to test for the appropriateness of asymptotic responses favored a time-dependent variant of the Munro model over one first described by Zhou and Shirley. A simple example of profit maximization is provided to show that maximum profit may not coincide with maximum catch under the assumption of a dome-shaped model.

Geographic variation in the abundance and morphology of the bryozoan Alcyonidium diaphanum (Ctenostomata: Alcyonidiidae) in UK coastal waters

The ctenostome bryozoan Alcyonidium diaphanum is widespread and abundant in the coastal waters of England and Wales. It was recorded in 77–90% of beam trawl catches in the eastern English Channel and southern North Sea, and in 53–73% of catches in the Bristol Channel and Irish Sea. The maximum catch rates in these two study areas were 1410 and 751 kg h−1 respectively. Alcyonidium diaphanum was most abundant in the greater Thames Estuary. Additional data from the North Sea indicated that A. diaphanum is widely distributed throughout the southern North Sea. Alcyonidium diaphanum was found intertidally in only seven of 99 locations sampled. Several different morphotypes were observed, ranging from cylindrical to lobate forms. The distribution patterns of various morphotypes are discussed.

Overview of cephalopod fisheries in Chilean waters

This paper describes the history of cephalopod fisheries in Chile over the past 40 years. Continuous monitoring of three species was undertaken between 1978 and 1999: Loligo gahi, Dosidicus gigas and Octopus mimus. Total cephalopod catches increased from 69 tonnes in 1978 (0.13% total mollusc catch) to 3503 tonnes in 1996 (3.64%). A maximum haul of 15,169 tonnes was taken in 1992 (11.27% total mollusc catch). Small-scale fisheries accounted for the majority of cephalopod captures and industrial catches were rare. L. gahi is caught year-round mainly in the south of Chile, with maximum catches in summer and autumn. Catches of D. gigas are also year-round, mainly concentrated in central Chile. O. mimus has been fished since 1978, although recorded as Octopus vulgaris until the 1990s. The O. mimus fishery is located on the north coast of Chile, and catches are made for the most of the year. Octopus has been landed in the south of Chile since 1991, and is considered as O. mimus in capture statistics despite the fact that several species are represented, including Enteroctopus megalocyathus.

Population densities and diversity of Calliphoridae (Diptera) around a nickel-copper smelter at Monchegorsk, Northwestern Russia

In the summer of 2000, we collected blowflies (Calliphoridae) in ten sites around the Severonikel smelter on the Kola Peninsula. Meat-baited funnel traps (three per site), operated from June 10 to August 30, yielding 973 specimens of ten blowfly species; eight species are reported from the Kola Peninsula for the first time. The maximum catch (495 individuals), obtained at the site located 1 km from the smelter, was due to the synanthropic preferences of the two most common species, Protophormia terraenovae and Cynomya mortuorum. Neither total abundance nor diversity of blowflies attracted by meat baits changed along the pollution gradient.

Seasonal distribution and spawning of small tunas (<i>Auxis rochei</i> and <i>Sarda sarda</i>) in the Northwestern Mediterranean

SUMMARY: Bullet tuna, Auxis rochei and Atlantic bonito, Sarda sarda are the most abundant small tuna species in the Mediterranean Sea. Both species are commercially exploited by a small-scale inshore fishery off the Catalan coast. Catches of A. rochei are highly seasonal, with maximum values in the warmest months (June to September), which is also the spawning period. Larvae of A. rochei were collected between July and September and were particularly abundant in July, when the mean sea surface temperature was 25.4oC. In summer, adults of this species migrate from the Atlantic to the Western Mediterranean, including the Catalan Sea, to spawn, but they are not found in this last region during the colder months. S. sarda is taken all year round in the Catalan Sea, with maximum catches from September to March, and minimum levels during the spawning period (May to July). Larvae of this species were only observed in July and larval abundance was considerably lower than that of larval A. rochei. Unlike A. rochei, S. sarda is resident over the continental shelf in the Western Mediterranean all year long, but at the beginning of summer, coinciding with the arrival of the other species, it moves to other areas in order to spawn.

Biology and fishery of the arched box crab Calappa convexa de Saussure (Crustacea, Brachyura, Calappidae) In the Southeastern Gulf of California, Mexico

The arched box crab (Calappa convexa) is commonly caught in gillnets as by-catch of the spiny lobster (Panulirus spp.) fishery in southern Sinaloa, Mexico, a locally exploited fishing resource. Crabs were sampled monthly from May 1998 to April 1999 and a total of 274 specimens (132 males and 142 females) were captured. The distribution of the resource was homogeneous (present in 72% of the samples) throughout the sampling area. The overall sex ratio (female:male) was 1:0.92 (χ2 > 0.05). The capture per unit effort (CPUE) varied from 0.81 g/100m2/h to 9.10 g/100m2/h. Maximum catch was obtained in June while minimum catches occurred in December and March. The CPUE values differed significantly (ANOVA P < 0.05) among the months of sampling. Crabs were caught on sand, rock and boulders, with 43% of the CPUE corresponding to rocky substrate. Mean size, based on carapace length (CL), was 72.5 ± 5.8 mm for males and 74.5 ± 7.2 mm for females. Individual size frequency distribution was unimodal and normal in males and unimodal and not normal in females, with the largest number occurring in spring (107) and winter (73). Reproduction occurred throughout the year, with peaks from April to August. Females reached sexual maturity at an estimated size of 75 mm (CL–50) and carried an average of 638,885 eggs. The mean size differed significantly between females (75.7 mm CL, SD = 7.3 mm) and males (72.8 mm CL, SD = 5.8 mm) (P < 0.05). The modal classes displayed a slight seasonal displacement (spring to winter) towards larger sizes. Analysis of the carapace width:length relationship shows variation during male and female development, specifically, in larger sizes (> 75 mm CL), females were narrower while the opposite occurred in males. Left and right chelae reached a combined fresh weight of 100 g, in males of about 75.0 mm CL, while in females this weight was reached at 79.0 mm CL.

Sex pheromone of Acrolepiopsis nagaimo Yasuda (Lepidoptera: Acrolepiidae), a predominant leafminer on Chinese yam in Tottori Prefecture: field evaluation and activity of the third component.

In field tests conducted in Chinese yam fields in Tottori Prefecture of Japan in 1998, maximum catches of Acrolepiopsis nagaimo males were obtained at ratios between 50 : 50 and 75 : 25 (=natural ratio) when 100 μg of a binary blend of (Z)-11-hexadecenyl acetate (Z11-16:Ac) and (Z)-11-hexadecenal (Z11-16:Ald) was baited in the traps. This attractiveness was apparently enhanced when 1% to 5% of (Z)-11-hexadecen-1-ol (Z11-16:OH) was added. When 2% Z11-16:OH was blended, the synergistic effect was apparent at high doses (≥100 μg/septum). The third compound, Z11-16:OH, was therefore confirmed as a sex pheromone component. The optimum blend for male attraction was determined to be 200–1000 μg/septum of a 50 : 50 : 2 blend of Z11-16:Ac, Z11-16:Ald and Z11-16:OH, respectively. More than ten times as many males were captured with this blend than with two 2- to 3-d-old virgin females.

Prevalence of fungal infections in adult Delia radicum and Delia floralis captured on the edge of a cabbage field

AbstractBrassiceye® traps baited with ethylisothiocyanate were modified and used to collect live adults of Delia radicum (L.) and Delia floralis (Fallén) (Diptera: Anthomyiidae) from the field to observe the prevalence of Entomophthora muscae (Cohn) Fresenius and Strongwellsea castrans Batko & Weiser. The traps were highly effective and selective for D. radicum and D. floralis. Of the flies identified, 98.4% in 1996 and 93.7% in 1997 were either D. radicum or D. floralis. In 1997 the maximum mean catch was as high as 82 flies per trap per day, and more than 80% of these were females.During both seasons E. muscae caused relatively high levels of mortality in adult populations of D. radicum and D. floralis. The fungus caused a total infection level of 17.9% in 1996 and 47.7% in 1997 with infection peaks of 82.4% in 1996 and 87.5% in 1997. Both years, a significant positive correlation was found between E. muscae prevalence and temperature. One infection peak was observed for S. castrans in 1996, and during that season the total S. castrans infection level was 18.0%. In 1997, the total S. castrans infection level was as low as 8.1%. There is no strong indication that the prevalence of E. muscae or S. castrans differs between either the fly species or sexes within species.

Circadian Activity of <I>Lygus lineolaris</I> (Hemiptera: Miridae) and Effectiveness of Sampling Techniques in Strawberry Fields

Mobility and distribution of adult tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), was studied on a day-neutral strawberry cultivar ('Selva') in 1991 and 1992 at L'Acadie, Quebec, Canada. On cage-covered plants, individuals were located mainly on reproductive parts. Study of the flight activity with sticky posts revealed that most captures were obtained < 1 m from ground level and that the time of the day at which the maximum counts occur varied among seasons. Three pest-sampling methods (white sticky trap, tapping of flower clusters, and D-Vac) were evaluated over continuous 24-h periods. Maximum captures of adults with white sticky traps were made at midday (1000-1400 hours), whereas the two other methods proved more effective at the beginning (0600-0800 hours) or the end of the day (2000-2200 hours) or during night time. For nymphs, maximum catches were obtained during the day with tapping and D-Vac; white sticky traps were ineffective. Because the D-Vac captures individuals present on all parts of the plant, these counts were used to monitor the effectiveness of the two other sampling techniques. The data suggest that tapping flower clusters throughout the day is a very effective sampling method to estimate nymphal tarnished plant bug populations in strawberries. However, sampling of populations with a high proportion of adults should take into account the bias caused by their flight activity, and sampling should be conducted early in the morning or at the end of the day.

Threatened Fishes of the World: Carcharias taurus (Rafinesque, 1810) (Odontaspididae)

Threatened Fishes of the World: Carcharias taurus (Rafinesque, 1810) (Odontaspididae)

Uncertainty and risk associated with optimised fishing patterns in a tropical penaeid fishery

Simulation was used to improve the management of prawn fisheries by indicating patterns of fishing effort which favour the harvest of more highly valued, larger animals. Attempts to use conventional local optimisation methods to find the optimum pattern of weekly fishing efforts were ineffective. Simulating annealing, a global optimisation method, was used effectively to find fishing effort patterns which maximised catch values. Sensitivity of the maximum catch value to the parameters used to model fishing and biological behaviour was also investigated. The optimum catch value was not sensitive to variations in trawl net selectivity or catchability parameters, although the optimum fishing season to obtain these maxima altered. In contrast, changes to biological parameters had a notable effect on the maximum catch value, despite compensatory changes to the optimum weekly pattern of fishing effort. The risk associated with achieving management goals using a range of fishing strategies was also assessed when recruitment timing and growth rates were modelled as partly stochastic. With uncertainty in recruitment timing, it was found that the optimum fishing pattern did not change. Uncertainty in growth rates made fishing earlier the best strategy, and increased harvest values in 43% of simulations

Analytical models for fishery reference points

Fishery reference points are widely applied in formulating harvest management policies. We supply precise mathematical definitions for several reference points in common use. We then derive analytical expressions for these quantities from age-structured population models. In particular, we explain how the maximum sustainable harvest rate and catch (h*, C*), two quantities of management importance, can replace the classical recruitment parameters ( alpha , beta ) in the Beverton-Holt and Ricker recruitment curves. We also demonstrate dependencies of various reference points on subsets of model parameters. Although our analysis is restricted to special cases, our models still have general utility. For example, simple calculations from analytical formulas enable checks on the output from more complex models and guide the choice of reference points for fishery management.

Population dynamics and fishery policy for migratory resources with two migration paths

The population dynamics and fishery policy for a migratory resource with two migration paths are analyzed, based on the supposition that the resource separates into two groups, each migrating along and caught on a different path, after reproduction in a limited area. Two possible mechanisms determining individual migration paths are considered: (i) ``nongenetically controlled'' migration and (ii) ``genetically controlled'' migration. Initially, the relationships between the resource population dynamics and the fishery are analyzed for both these cases. Based on these results, the optimal fishery policy for each migration path is analyzed. Two criteria to be maximized were considered: (i) the ``game situation,'' which aims to maximize catches on each fishery path, and (ii) the ``cooperative situation,'' which aims to maximize the total, overall catch on both paths. In the case of genetically controlled migration, a fishery based on one path negatively affects recruitment on that path but positively affects recruitment on the alternative path. In both the nongenetically controlled and genetically controlled migration cases, the cooperative policy resulted in higher overall maximum catch, especially in the latter case. In the genetically controlled migration case, convergence to equilibrium is often slow, the rate being affected by density dependence of mortalities.

Relationship between temperature and fluctuations in sandfish catch (Arctoscopus japonicus) in the coastal waters off Akita Prefecture

The sandfish (Arctoscopus japonicus) catch in the coastal water off Akita Prefecture have fluctuated greatly over the period 1962–1990. The difference between the maximum and minimum catches over those years is more than 200 times. The aim of this paper was to investigate the relationships between water temperature and the fluctuations of the catch. Using the fuzzy logic approach, the water temperatures measured in the different points off the Prefecture were summarized as an index which would indicate the variation of water temperatures. In this study, the sensitivity tests showed that the index inferred using the water temperatures observed in 100–150 and 200–300 m depth at 9 and 65 km off the coast with time lags 1, 2, 3 and 4 years could explain the fluctuation of sandfish catch. That is, large changes in catch can be simply explained by the fluctuation of water temperatures.

Flight Activity of Insects within a Jamaican Cave: In Search of the Zeitgeber

Flies of several families (Scatopsidae, Phoridae, Milichiidae) exhibit clear diurnal flight activity patterns in constant total darkness in Dromilly Cave, Jamaica. Most scatopsids were caught on adhesive traps during daytime (>95% between 0630 and 1830) with maximum catches about midday; phorids showed little evidence of cyclic activity although slightly more flew during the last half of the night and early morning (59% between 0000 and 1030); and most milichiids were caught during the day (>70% between 0630 and 1630) with slightly larger catches before midday. Apparently, those insects in the lightless region of the cave that display activity rhythms synchronize their flight activity to the diurnal cycle even though they are unable to see daily light intensity changes outside. Bats flew within the cave throughout the night with activity maxima at dusk and dawn, but they never flew during the middle of the day. We suggest that the flies used bat activity as a secondary zeitgeber. Additional key words: cave insects, Diptera, Scatopsidae, Phoridae, Milichiidae, bats, rhythm Small flying dipterans, most no longer than 2 mm, are abundant in many Jamaican caves with large bat populations (Peck 1975, 1992; Meyer-Rochow & Stringer 1997). Little is known about these insects except some aspects of their behavioral ecology (Stringer & Meyer-Rochow 1994) and their distribution in Dromilly Cave (Stringer & Meyer-Rochow 1996). Specimens representing the families Scatopsidae, Phoridae, and Milichiidae (in this text collectively referred to as cave flies) were taken to the Institute of Jamaica for comparisons with fly specimens held in the national insect collection, but identifications failed as the collections present were based on flies caught in the open. This suggested to us that the cave flies were absent, or at least very rare, outside caves. How little is known about Jamaican cave flies is highlighted by the fact that Matile (1994), in a recent review on cavernicolous dipterans of the world, does not list a single from Jamaica. One is inclined to think that the statement by Farr (1984) that nearly every recorded from Jamaica belongs to a separate phyletic line or group ... and only four groups are represented by more than one species (referring to Culicidae) could apply to cave flies as well. Most of the cave flies are saprophages, feeding on bat guano, carrion, and plant debris; a small number, most a Author for correspondence. Present address: Institute of Arctic Medicine, University of Oulu, SF-90220 Oulu, Aapistie 1., Finland. E-mail: vmr@sun3.oulu.fi notably streblids and culicids lead parasitic lives. Worldwide, 30 genera of scatopsids are recognized, but larvae are known for only 8 of them (Werner 1995). We found that the numbers of scatopsids caught in adhesive traps left in a permanently dark chamber of Dromilly Cave varied markedly on different dates and seemed to depend on the time of day. The results suggested to us that the scatopsid flies-and possibly others-might have a daily flight activity peak in the middle of the day, in spite of their permanently dark surroundings. Since extremely evolved cavernicolous animals ... lack circadian periodicities of locomotion (Lamprecht & Weber 1985) and are essentially non-rhythmic (Ford & Cullingford 1976), we investigated whether the Jamaican cave flies showed activity rhythms and, if so, what factor(s) might govern them. One possibility was that the insects' activity was related to the activity (or presence) of the bats within the cave, so the latter were also monitored.

Studies on the Sex pheromone of the diamondback moth Plutella xylostella (Lepidoptera: Yponomeutidae) in India

AbstractMarked male moths of Plutella xylostella (Linnaeus) released at up to 12 m from a sticky delta trap baited with synthetic pheromone, were caught in significantly higher numbers than moths released at greater distances, both in downwind and upwind directions, from the traps. Maximum catches were obtained when the traps were set at 30 cm above the crop level. Continued exposure of septa in the field led to a progressive reduction in catches, and catches were significantly reduced after 28 days. Newly emerged virgin female moths attracted significantly more male moths than one day old or older virgin female moths. Five day old virgin females attracted no male moths. When virgin females were used as a bait in the field, the peak catch of males was between 1600 and 1800 h. Tests at two field locations revealed that, at the concentration tested, synthetic sex pheromone attracted a similar number of moths to the number attracted by 10 virgin females in delta traps, and significantly more than 8, or fewer virgin females.

Sampling larval fishes with a nightlight lift-net in tropical inshore waters

The applicability of a nightlight lift-net for sampling ichthyoplankton assemblages was evaluated in inshore habitats off southwestern Puerto Rico. The effects of lunar periodicity, habitat, light duration, and gear type (nightlight vs. plankton tow) were investigated. Overall, 36 piscine taxa were collected with the nightlight lift-net from inshore habitats (i.e. coral reef, mangroves, seagrass bed, sand flat). Larval fishes (80.6%), particularly clupeids ( Jenkinsia spp. and Harengula spp.), were the predominant developmental stage collected. Juvenile and adult fishes accounted for 14.7% and 4.7% of the catch, respectively. Nightlight collections showed marked patterns in larval fish abundance during different lunar phases with peak catchability occurring during the new moon phase. New moon samples accounted for 65.7% of all larvae collected during the complete lunar cycle. Significant lunar effects were observed in coral reef, seagrass bed, and sand flat habitats. No lunar related trends were observed in mangrove cay or nearshore mangrove habitats. Spatial patterns in nightlight catches were present with many taxa showing significant differences in abundance among habitats sampled. During lunar periodicity trials, catches were highest in the seagrass bed and coral reef habitats. Taxonomic diversity was greatest in seagrass bed and coral reef habitats with 16 and 11 taxa, respectively. Low abundance and taxonomic diversity characterized mangrove cay and nearshore mangrove habitats; however, increases in taxonomic diversity were observed during a fall survey of nearshore mangrove habitats. Light duration experiments indicated that larval abundance increased with increasing sampling duration and maximum catch per unit time was obtained at 10 min. Longer and shorter durations resulted in lower catch per unit effort and greater coefficients of variation. Trends in species composition and development stage were detected among nightlight lift-net and plankton net-tow methods.

The Puerulus Settlement of Red Spiny Lobster (Panulirus Interruptus) in Bahía Tortugas, Baja California, Mexico

AbstractThe settlement of the puerulus stage of the Red Spiny Lobster (Panulirus interruptus) was measured in Bahía Tortugas, Baja California, using artificial collectors of the GuSi type. In the period 1993-1995 monthly sampling during the new moon phase was carried out. Catch rates per collector ranged from 1 to 10 pueruli. Mean catch per site ranged from 0 to 2.52 puerulus/collector/new moon phase. The general settlement pattern showed a conspicuous seasonal cycle where autumn was the dominant season, during spring there was a second minor peak. In both years September and October showed the highest catches, but September 1994 to February 1995 was a longer settlement period with maximum catches. The carapace length varied from 6.5 to 33.5 mm, 7.5 mm being the most frequent size. The season of maximum settlement seems to be related with a maximum sea temperature (20 to 21°C) which in Baja California occurs during the autumn.