Validation of the accuracy of household reporting of subsistence fishing catch and effort: a Fijian case study

Abstract  The accuracy of household reporting of subsistence fishing catch and effort and seafood consumption on the Fijian island of Ono-i-Lau was studied. A creel survey was carried out concurrently to validate the household survey data. Reported estimates of fishing participation, effort, and fish consumption were not significantly different to the creel survey estimates. Householder's appeared to overestimate the number of fish from the most abundant family Lethrinidae, and underestimate rarer fish. However, there was no significant difference between the reported and observed contribution of the majority of finfish families and invertebrate taxa. The reported and observed catch rate estimates were not significantly different, indicating that Ono-i-Lau villagers are relatively accurate in their estimation of the number and size of fish from recalled catches.     

Density and temperature dependence of gill net catch per unit effort for perch, Perca fluviatilis, and roach, Rutilus rutilus

Abstract  The densities of perch, Perca fluviatilis L., and roach, Rutilus rutilus (L.), were estimated in six and three lakes, respectively, using mark–recapture and ranged from 25–1064 perch ha⁻¹ and 865–2749 roach ha⁻¹. Effects of fish density, net type and water temperature on catch-per-unit-effort (CPUE) were analysed by generalised linear models (GLM) and generalised additive models (GAM). GAMs were fitted to estimate the simultaneous linear and nonlinear effects of temperature and density on CPUE. These models showed significant nonlinear effects of density on CPUE – mostly for perch, and also for both species at high densities. The models also revealed that both species had distinct density–temperature criteria of expected maximum CPUE and zero CPUE values. Because of the nonlinear relationship between CPUE and density, it was concluded that CPUE should be used with caution as a proxy of density.     

Fish stock assessment of the northern New Caledonian lagoons:3 – Fishing pressure,potential yields and impact on management options

The potential yields of demersal reefal and lagoonal finfish, which are valuable for trade or consumption in the Northern Province of New Caledonia, are unknown. Fishing pressure was estimated from tally-sheets of professional fishermen to assess trade fishing and a household consumption survey to assess subsistence fishing. Total yield was estimated to be 1 326 tonnes in 1995, 94 % of which correspond to subsistence fishing. Most of the catches were taken from the east and west coasts; in the north zone (Bélep Archipelago) catches were very low. From this fishing pressure and the total stock values, the maximum sustainable yield (MSY) was estimated to be 12 600 t, which was about 10 % of the total stocks assessed in the Northern Province (138 300 t). This MSY was dominated by five families, namely Lethrinidae, Acanthuridae, Scaridae, Serranidae and Lutjanidae. The results suggest that fishing effort in the Northern Province of New Caledonia could increase without endangering the stock. However, on a smaller geographical scale, some locations (Koné and Népoui on the west coast), reef habitats (near-reef areas) or species groups (fish caught by line) were already being intensively fished. Fishing techniques should be diversified so that part of the fishing effort be redirected toward the least heavily exploited groups of species and biotopes.     

The reef fisheries surrounding the south-west coastal cities of Madagascar

The artisanal fishery in south-west Madagascar, around the coastal cities of Morondava, Morombe and Tuléar, is particularly active. In the Morombe and Tuléar regions, fishing pressure focuses on coral formations close to landing sites and reef fish constitute the main part of the catch (Lethrinidae, Haemulidae, Siganidae). In Morondava, fishing is practised very close to the shore on sandy substrates, but also on offshore reef shallows. The catches are more diverse and made up of reef fish (Serranidae, Lutjanidae) and non-reef species. Fishing from Morondava targets the highest trophic level of the coral reefs (piscivores/macroinvertebrate feeders: 87% of the catch) whereas in Tuléar and Morombe the higher fishing effort means that lower trophic levels are targeted to maintain catches. Despite the high fishing effort, especially around Morombe and Tuléar (standardizing fishing effort of 5200 hook h km^–2 year^–1 and of 12 300 hook h km^–2 year^–1, respectively), the catch per unit effort (CPUE) is still relatively high; it varies from 0.6 to 2 kg h^-1 per person over the whole zone and seems to be more linked to the fishing method used and to the degree of professionalism than to variations in the abundance of the resources surrounding the three cities. The relatively high CPUE can probably be explained by a continual immigration and/or recruitment on these fishing grounds. The fish originate from sectors that are far from towns and weakly exploited. A sociological study was carried out concurrently with the fishing survey and focused on present-day transformations within the fishing community.     

An assessment of catches and harvest of recreational shore angling in the north of Portugal

Abstract  Recreational shore angling in the Atlantic Ocean between Moledo and Aveiro (Portugal) was examined using roving creel surveys (March/September 2001). Cooperation was high (90% of 2310 anglers approached). At least 39 species of fish were caught at a rate of approximately 0.5 fish angler h⁻¹. An estimated 7319 kg of Dicentrarchus labrax (L.), with 45.6% below the minimum legal size, and 2040 kg of sea breams (genus Diplodus ), correspond to 5.75% and 1.19% of the commercial landings in the same geographical area, respectively. The results shed light on a number of issues relevant to integrated coastal management, including temporal and spatial distribution of fishing effort, species caught, sizes of fish, catch rates, and factors influencing catches and angler satisfaction. Whilst the results suggest that the catches of sea breams and sea bass by day-time recreational shore angling in northern Portugal are small compared with commercial fishing, other recreational activities, such as boat fishing and spear-fishing, must be assessed.     

Temporal changes in fishing motivation among fishing club anglers in the United States

Responses from freshwater anglers (n = 4287) to a nationwide survey of the US fishing club members were used to assess differences in the importance of 16 fishing motivation items between 1987 and 1997, dates that preceded and followed a period of substantial decline in recreational fishing participation in the US. Comparison of respondents’ motivations for fishing in 1997 and 10 years earlier indicated consistency in the paramount importance of being outdoors, relaxation and the experience of the catch. However, the importance of family recreation and being with friends in 1987 were replaced by escape items in 1997. Anglers with fewer dependents and living in areas with higher population density were more likely to decrease the importance of family recreation. Younger anglers were more likely to decrease the importance of being with friends. Anglers who had higher household income, fished more and had higher fishing expenditures were more likely to decrease the importance of obtaining fish to eat. The results of this study suggest that managers should be less concerned about angler opposition to liberal regulations that allow anglers to harvest fish, and that heightened efforts to recruit and retain recreational anglers, which presently focus on family recreation, should be broadened to include outdoor experience, relaxation and escape aspects of fishing.     

Potential yield estimates of unexploited pelagic fish stocks in Lake Malawi

The biomass of the offshore pelagic fish of Lake Malawi was estimated at 168 400 t and is currently unexploited by a fishery. This biomass comprises, by weight, 81% Cichlidae, 15% catfish and 4% Cyprinidae. A Beverton and Holt dynamic pool model was used to estimate potential sustainable yields and to forecast likely changes to the size and age structure of the fish populations under various levels of fishing effort. The total sustainable yield from the offshore fish population was estimated at 34 000 t yr^–1 and, if harvested, would almost double the yield of fish from the lake. Potential yields on an areal basis are low (14.2 kg ha^–1 yr^–1), but are consistent with expectations from studies of pelagic ecosystem productivity.     

Angling pressure, yield and catch per effort of grayling, Thymallus thymallus (L)., and brown trout, Salmo trutta L., on the rivers Glomma and Rena, southeastern Norway

Abstract Postal questionnaires, interviews and accurate reports from anglers were used to study angling activity, yield and catch per effort of grayling, Thymallus thymallus (L.), and brown trout, Salmo trutta L., on three stretches of the regulated river Glomma and two stretches of its tributary, the river Rena in southeastern Norway. Angling activity was expressed as hours angling per kilometre of river and varied from 364 (CL 245–598) to 1337 (CL 912–1991) h km^-1. Grayling and brown trout dominated the catches. The catches were estimated between 476 (CL 334–659) and 753 (CL 517–1155) grayling and brown trout per kilometre river stretch. The mean weights were estimated between 216 and 353 g for grayling, and 260 and 395 g for brown trout. The yield of grayling and brown trout was estimated between 8.7 (CL 6.1–12.4) and 46.4 (CL 34.9–62.3) kg ha^-1 yr^-1. The quotient grayling/brown trout in the catches varied between 0.41 and 5.1, and was found to be significantly negatively correlated with angling effort ( r = - 0.838, P <0.05). Catch per effort was estimated between 132 (CL 82–218) and 382 (CL 287–513) g h^-1, and was also negatively correlated to angling effort, according to: Catch per effort (g h^-1) = - 0.210 × effort (h km^-1) + 405 ( r = and 0.899, P <0.02).
Angling activity in earlier years was determined from number of permits sold where data were available. On stretches where angling activity was moderate, there was a tendency towards increase, whereas on stretches where activity had been high for several years, the activity seemed to have stagnated, indicating that a saturation had been reached.     

Relationships between catch and effort in Fijian multispecies reef fisheries subject to different levels of exploitation

Abstract The catch-per-unit-effort (CPUE) and value-of-catch-per-unit-effort (VPUE) of reef-associated fish species from six Fijian native fishing grounds ( qoliqoli ) subject to different fishing intensities were determined using records of fishing activity from a voluntary logbook scheme. Line and spear fishing techniques were used for more than half the total fishing time (h person^-1 d^-1) in all qoliqoli , and yet the favoured technique in a given qoliqoli was frequently less efficient (lower CPUE) than other techniques. The popularity of relatively ineffective fishing methods implies that fishermen did not always attempt to maximize their catch rates. To compare fishing effort in different qoliqoli , all effort was rescaled on the basis of its recorded efficiency (measured as multispecies CPUE) and expressed as hours equivalent to boat-based spear fishing over coral by day to catch fish for sale. Total fishing intensity in the six qoliqoli ranged from 72 to 4310 h km^-2 reef year^-1. The relationship between catch and effort was linear at all fishing intensities, suggesting that the qoliqoli were all fished on a sustainable basis. Furthermore, whilst there was a significant difference in CPUE and VPUE between the one or two qoliqoli with lowest fishing intensity and all the others, there were no significant differences between these other qoliqoli in terms of the VPUE of the saleable multispecies boat catch or the CPUE of species from piscivorous and carnivorous genera ( Epinephelus, Lethrinus and Plectropomus ) which the fishermen prefer to catch.     

Estimation of northern pike population sizes via mark–recapture monitoring

Abstract Estimates of population size are needed in populations targeted by recreational fisheries, to determine their conservational status and to formulate fishing regulations. Mark–recapture monitoring is a promising tool for this because of the increased popularity of catch‐and‐release angling. Northern pike, Esox lucius L., population sizes were estimated in four lakes based on experimental mark–recapture fishing using a hierarchical Bayesian model that also estimated natural mortality. The approach was compared with output from traditional Petersen’s population size estimates. Despite intensive fishing with multiple gears, the population size estimates suggested that a substantial proportion of individuals remained unobserved by fishing. Petersen’s estimates depended on the assumed rate of natural mortality, and no mortality rate scenario matched with the Bayesian estimates. Consequently, the number of individuals caught by recreational anglers is a poor proxy of population size for which estimations should be carried out using a modelling approach that also estimates natural mortality.     

Population ecology of cave armoured catfish, Ancistrus cryptophthalmus Reis 1987, from central Brazil (Siluriformes: Loricariidae)

Abstract –  The population ecology of Ancistrus cryptophthalmus (Reis 1987) was studied by mark–recapture technique in caves from the São Domingos karst area, State of Goiás, northeastern Brazil. Total population sizes estimated for Angélica and Passa Três Caves were 20,000 and 1000 individuals, respectively. Densities around 1.0 individuals per m² in Angélica, Bezerra and São Vicente I Streams, and 0.6 individuals per m² in the smaller Passa Três Stream may be considered high for cavefish standards, as well as for epigean loricariids. As expected for benthic grazers, cave catfish are highly sedentary. The distribution of size classes did not differ among caves and within the same cave throughout the studied dry seasons; on the contrary, the condition factor decreased throughout this period probably because of the progressive depletion of organic matter available as food. Low proportions of mature individuals, low growth rates (average = 0.5 mm month⁻¹) with cases of negative growth and high longevities (8–10 years) point to a precocial lifestyle, typical of troglobitic species.     

Estimate of reproductive value of the big eye Priacanthus macracanthus in the north-eastern waters off Taiwan

ABSTRACT: The reproductive value and population status of the big eye in the north-eastern Taiwan waters was estimated by demographic analysis using available life-history parameters. Life-history tables were constructed using estimates of natural mortality ( M ) of 10.4920/year for age 0 and 0.3256/year for ages 1–9, with a maximum age of 9. Age-specific batch fecundity ( F_e ) was from F_e  = 1391.34e^{0.1782 FL} . The age-specific proportion of maturity was estimated from the relationship between the proportion of female maturity ( Pr ) and fork length ( FL ): Pr  = 1/(1 + e^{15.081−0.796 FL} ). Females mature at age 3 and mature females reproduce every year. The population increase rate (λ) was estimated to be 20.5% per year and the generation time ( G ) was 6.25 years without exploitation. The net reproductive value ( R₀ ), generation time and intrinsic rate of natural increase ( r ) decreased with increased fishing mortality. For fixed fishing mortality, when F  = 1.2/year and fishing started at age 3, R₀ was estimated to be 1.0 and the population was considered to be in equilibrium. For age-specific fishing mortality, when fishing started at age 3, R₀ was estimated to be 0.96/year, G being 6.18 years, and the population decreased 0.7% per year. The big eye population had a strong resilience as long as F  < = 1.3/year started at an age that was older than the age at maturity (i.e. 3 years old) but would decline when intensive fishing ( F  > = 1.2/year) started at age 2 or younger. Sensitivity analysis indicated that the mortality of age 0 is the most sensitive parameter in demographic analysis.     

Pike predation on hatchery-reared Atlantic salmon smolts in a northern Baltic river

Abstract –  The effect of pike Esox lucius predation on the mortality of newly stocked Atlantic salmon Salmo salar smolts was investigated in the Pyhäjoki River, Finland. The number of smolts eaten by pike was assessed by estimating the size of the pike population (mark–recapture experiment) and studying the stomach contents of pike. Before recapturing the pike, approximately 39,700 smolts were stocked upstream of the 2.5-km-long (89-ha) research area. The estimated size of the >40-cm pike population was 1507 (95% CL 1012–4731) individuals (17 pike and 29.8 kg·ha⁻¹). Pike were estimated to eat 29% of the released smolts during 1 week. The diet of the pike in the research area consisted almost entirely of smolts, whereas in the reference area with no stocked smolts, the meal sizes were significantly smaller and the importance of smolts as prey was substantially lower. Pike <40 cm had not eaten any smolts, probably indicating a size refuge for the smolts, or alternatively fear of intraspecific interactions or cannibalism of pike.     

Benefits of repeated stocking with adult,hatchery‐reared brown trout,Salmo trutta,to recreational fisheries?

Abstract  Recaptures of adult, hatchery-reared, brown trout, Salmo trutta L., and fishing time from anglers were used to evaluate the benefits of stocking programmes with repeated releases of adult brown trout. The recapture rate varied between 17% and 29%. The time between stocking and capture (referred to as residence time) varied between 1 and 160 days (median 3–49 days). Between 67% and 84% of trout caught in the river were recently released fish. Fishing effort increased after stocking, thereby increasing the impact of angling on wild stocks. Stocking with adult brown trout decreases the impact of angling on wild trout only if the time spent fishing by all anglers is kept stable. Furthermore, because of the short residence time of stocked trout, long-term impacts through competition for space and food, or genetic impact through introgression, are limited.     

The relationship between stock and catch and the effect of bait on catch as determined for a UK recreational catch and release fishery

Abstract Twelve anglers fishing in a UK navigation canal for a total of 42 h caught 567 fish, mainly gudgeon, Gobio gobio (L.) ( n =306) and roach, Rutilus rutilus (L.) ( n =253) at an average catch rate of 13.4 fish angler-h⁻¹ or 128.5 g angler-h⁻¹. The species and size of fish caught were compared with the numbers determined by depletion estimates at six sections of canal using micromesh seine netting. Fifty four percent of fish caught in the net were < 60 mm FL. Gudgeon (60–99 mm) were over-represented in the anglers' catches whilst roach (60–99 mm) were under-represented. The size distribution of roach and gudgeon caught by anglers using two types of bait (small maggots and chironomid larvae) was examined and smaller fish were found to be caught using the latter.     

Population dynamics of tambaqui, Colossoma macropomum Cuvier, in the Lower Amazon, Brazil

Fishery statistics and length data series for Colossoma macropomum Cuvier obtained during 1992 and 1993 in the Lower Amazon, Brazil were used to describe the fishery and to estimate growth and mortality rates. Mean population parameters were L _∞ = 119.85 cm (total length), W _∞ = 33.4 kg, K = 0.228 year^–1, C = 0.505, Winter Point = July, M = 0.445 year^–1, F = 0.94 year^–1 and L_c = 28.29 cm. Yield-per-recruit analysis showed that an excessive fishing effort and principally a very low length at first capture lead to an increase in overfishing in the region. Corrective measures are recommended.     

Microhabitat use, movements and abundance of gilt darters (Percina evides) in southern Appalachian (USA) streams

Abstract –  We examined microhabitat use by gilt darters ( Percina evides ) in two streams in the south-eastern USA. Darters were over-represented in erosional microhabitats with higher average velocities and more cobble. Male darters tended to show stronger selection than females. Size-based analyses showed that larger (≥60 mm) gilt darters tended to use microhabitats with more heterogeneous substrata and more boulder than smaller (≤59 mm) darters. We also conducted a short-term movement study and calculated population estimates based on mark–recapture data in autumn 2005. Darters moved both long and short distances with 40% of all recaptures occurring within 5 m of the initial capture point. Using Program mark and model-averaged parameter estimates gilt darter density was 0.31 darters·m⁻² (225 darters/730 m²). Conservation of this species will require the preservation of erosional habitats in streams.     

Characteristics and economic contribution of a developing recreational fishery in southern Angola

Abstract  The characteristics and contribution of a developing recreational fishery to the local, regional and national economy of Angola were evaluated in 2006. Annual angling effort was 13 435 h, while the estimated total catch of the three target species [leerfish, Lichia amia (L.), west coast dusky kob, Argyrosomus coronus (Griffiths & Heemstra) and shad, Pomatomus saltatrix (L.)], was 5913 fish with a mass of 27 975 kg. Catch per unit effort (CPUE) for all teleost species combined was 0.44 fish per angler h⁻¹ and 2.08 kg per angler h⁻¹. Total harvest of the three species was 576 fish with a total mass of 2221.6 kg. The total contribution of this recreational fishery (mostly anglers from South Africa) to the local economy was US$ 1007 per harvested fish and US$ 243 per harvested kg. This equated to a contribution to the local, regional and national economies of US$ 151 685, US$ 44 767 and US$ 344 364 respectively. Although the regional contribution was less than half of the national contribution, it was regionally significant when the low population density and the general absence of other formal sector employment opportunities are considered. As a result of the largely undisturbed nature of the southern Angolan coastline, the catch, effort and CPUE information was considered suitable as a baseline for a cost-effective method of future fisheries monitoring in the region.     

Tracing possible drivers of synchronously fluctuating species catches in individual logbook data

Abstract Recreational fisheries statistics can provide valuable information on the dynamics of fish stocks and their exploitation. For some reservoirs in the Czech Republic, there are conspicuous synchronous fluctuations in catches of different species that might be caused by fishing skills and strategies. This study describes a method that could detect signatures of such phenomena in individual logbooks. It classifies anglers by species reported during 1 year and compares the resulting angler groups by group size, fishing effort, catch per unit effort (CPUE) and annual catch. The method is illustrated by data from one reservoir, showing that the number of generalist anglers who caught several species was higher than expected. Generalists also had higher catches and effort but lower CPUE than specialists who caught only one of the species. The results indicate that generalist anglers with a low degree of specialisation and high effort could contribute to long‐term correlations in species catches.     

When is a fisher (not) a fisher? Factors that influence the decision to report fishing as an occupation in rural Cambodia

In the developing world, the majority of people who fish in inland areas do so primarily for subsistence needs. This suggests that survey or census questionnaires which collect information concerning the occupations of respondents will underreport the number of people who fish, and corollary to this, misrepresent dependence on fishing as a support service for food and supplemental income. This study uses the results of a household survey conducted in 37 villages across Cambodia to quantify the amount of fishing that is done by inland fishers who do not report fishing as a primary or secondary occupation. The study also identifies the household characteristics which influence the decision of an individual who fishes to report fishing as an occupation. Fifty‐eight percent of households whose members engaged in fishing activities did not report fishing as an occupation. Individuals whose household owned farmland, earned off‐farm income and fished primarily for subsistence needs were significantly less likely to report fishing as an occupation. When assessing the importance of fishing to inland rural communities for the purposes of rural planning and policy development, relying solely on census‐style occupation or employment data will misrepresent the contributions of subsistence fishing to household welfare.