Average CPUE Research Articles

Population structure and reproduction of a migratory fish Leporinus piau (Characiformes: Anostomidae) in a semiarid tropical reservoir, Brazil.

Migratory fishes have been seriously impacted by the building of reservoirs and because of the negative effects of these projects such as the interruption of migratory routes, reduction or elimination of spawning/feeding areas, and initial development can influence the population structure the migratory fishes, resulting in reduction in abundance. Leporinus piau is migratory fish widely distributed in the watersheds of the Brazilian semiarid and it is of importance for artisanal and sport fishing. The goal of the study was to evaluate the population structure and reproductive dynamics of the migratory species Leporinus piau in the Pau dos Ferros Reservoir, which is located in the semiarid region of Brazil. The CPUE, length structure, length-weight relationship, length at first maturity, sex ratio, gonad development and IGS were analyzed. Collections were performed quarterly between February 2011 and November 2012 using gillnets. The captured fish were counted; the standard length (cm) and total weight (g) were measured, and dissected to determine the sex and gonad maturity stage. The rainfall and reservoir water levels were recorded, and their correlations with the reproductive period and CPUE were analyzed. A total 549 individuals were captured. The average CPUE varied between 0.0259 individuals/m2*h (May/2011) and 0.0008 individuals/m2*h (August/2012), and significant differences were observed; however, significant correlations were not observed between rainfall and reservoir levels. The standard length varied between 5.9 cm and 20.7 cm, and the weight varied between 4.16 g and 271.5 g. A histogram analysis revealed that the 5-10 cm standard length class was the most abundant for juveniles and that the 10-15 cm class was the most abundant for adult females and males. The weight-length relationship was best fit by the equation log10Wt = -1.57711 + 3.00707 Log10 Ls, and the species presented isometric growth. The estimated length at first maturity was 12.76 cm. A total of 148 males and 82 females were collected (1.81:1, M:F), and these values were significantly different. The highest GSI was observed in February 2011 for both females (10.69) and males (5.72), and the GSI was significantly and positively correlated with rainfall. We concluded that the L. piau population is established in the reservoir and found that its reproduction period occurred during the rainy season between February and May.

Study of Season with Fishing Pole and Line Skipjack Fishing Base in PT. Radios Apirja, Sorong-West Papua

This study aimed to analyze the index skipjack fishing season which fishing base in PT Radios Apirja, Sorong-Papua Barat. Analysis of the data used is to use Presentation Methods average based on time series analysis that Determine the total catch per effort for each month for cascading data researched, created the series order CPUE per month for five years from 1 to 60, adding up the five CPUE each of the 12 months in five years, summing 60th CPUE, then a total of 60 CPUE divided by 12 to get an average per month in these five years. Total each CPUE respectively 12 months reduced by an average CPUE to get the index of catching season, and by using a chart or graph. The index value indicates that more than one fishing season, while the value of the index is less than 1 indicates no fishing season. The results showed that the business of catching skipjack by pole and line in the waters of Papua bird's head is done throughout the year, and catches fluctuate on a monthly basis, while the fishing season occurs from February to April and July to August.

RAPA WHELK (Rapana venosa Valenciennes, 1846) FISHERY ALONG THE TURKISH COAST OF THE BLACK SEA

In this study, the current situation of an invasive gastropod rapa whelk fishery with dredges and hookah systems were comparatively evaluated. On the other hand, a socio-economic analysis was conducted to evaluate the hookah (diving) system via face to face interviews. There were 207 vessels legally operating in the research area for whelk fisheries 108 of which were using the hookah system. Mean length and engine power of the hookah vessels were 8.8 m and 65 HP, respectively. It was also found that the average CPUE was 1050 kg/day and income rate was 79%, suggesting that whelk fishing had a high economic gain. Each of the hookah vessels provided an employment to average 3 individuals. According to the results, mean lengths of whelks harvested with dredges and hookah vessels were 5.61 cm and 5.83 cm, respectively. Length-weight relationship of the total production was determined as W=0.0223L 2.965 (R 2 =0.85). It was concluded that the hookah system is more environmentally friendly method for the ecosystem than dredges.

Effects of hydro-climatic fluctuations on catchability of fish in Vavuniya reservoir, Sri Lanka

Catch assessment and frame survey were performed to estimate the species wise and total catch in the Vavuniya reservoir along with hydro-climatic factors. Relationship between the hydro-climatic factors and species wise catch statistics were determined from calendar year, rainfall (RF) and water level (WL) based quarters of the annum. Irregularity in the rainfall pattern shifted the heavy rainfall based quarter from October-December to February-April in 2013. Significant variation (P 0.05, r=-0.327) However, there was a strong negative correlation between monthly average WL and CPUE in terms of kg/fisher/day. There were 5 exotic, 13 indigenous and 1 endemic (Esomus thermoicos) species identified. Oreochromis niloticus contributed 79%, Cirrhinus mrigala (8.6%) and Channa striata (7.6%) of the catch. Data obtained from this study may be used as a baseline for the sustainable management and to achieve optimal catch.

The Moray Eel Fishery in the Seagrass Beds of Siquijor Island, Central Philippines, with Remarks on Two New Philippine Records of the Genus Gymnothorax

In this paper, the researchers document for the very first time in detail the moray eel capture fishery in the seagrass beds of Siquijor Island, Central Philippines. The process of deploying the bamboo traps, gathering of baits, andcatch-per-unit effort (CPUE), income-per-unit effort (IPUE), and the possible impact of an increasing number of moray eel fishers are also discussed. The researchers noted a very low average CPUE of 1.32±0.19 S.E. kg/person/hr and a corresponding Income-per-unit effort (IPUE) of 59.75±9.9 S.E.. Philippine Pesos/person/hour. Sustainable fishing practices of catching moray eels are also highlighted. Apparently, two new records of muraenid eels of the Genus Gymnothorax for the Philippines are also briefly annotated. Keywords - Fishery, Moray eel, Catch Assessment, Siquijor Island, Philippines, Southeast Asia

Spatial and temporal variation in recovery of hatchery-released red drum (Sciaenops ocellatus) in stock-enhancement of Texas bays and estuaries

Spatial and temporal variation in recovery of hatchery-released red drum (Sciaenops ocellatus) was assessed in nine bays and estuaries along the Texas coast. Sixteen nuclear-encoded microsatellites were used to identify a total of 167 hatchery-released fish among 4325 red drum sampled between the fall of 2006 and the spring of 2009; these were added to 41 recovered hatchery-released fish identified in a prior study of 1332 red drum sampled from Galveston and Aransas bays in the fall of 2005 and spring of 2006. Recovery of hatchery releases across bays and years ranged from 0.28% to 17.65%. Of the 208 recovered hatchery-released fish, 158 were age 0–1, 46 were age 1–2, and four fish were age 2–3. The distribution of recovered hatchery-released fish and wild fish differed significantly across sampling periods within and among bays or estuaries. Allelic richness in recovered hatchery-released fish was significantly lower than in both hatchery brood fish and wild fish. In addition, recovered hatchery-released fish were produced by fewer dams, sires, and dam×sire combinations in 2005 and 2006 and by fewer dams and sires in 2007 than would be expected if reproductive success was distributed randomly among brood fish. The spatial distributions of recovered hatchery-released and wild fish deviated from random expectations for samples from the Upper Laguna Madre in the fall of 2006 and spring of 2007 and from West Matagorda Bay in the spring and fall of 2008. Correlation and principal components analysis identified a significant, positive relationship between annual average CPUE and relative annual mortality. No relationship was observed between the number of fish released per hectare and the percentage of recovered hatchery-released fish. Comparisons to other studies of red drum stock enhancement are discussed.

荣成俚岛人工鱼礁区游泳动物群落特征及其与主要环境因子的关系

Based on the environment and nekton data obtained from seasonal surveys in Lidao artificial reef(AR) and control zones of Shandong province between May 2009 and February 2010,this paper analyzed the species composition of nekton community in the two zones.Variations on temporal-spatial distribution patterns and community structure of nekton community were determined by using Margalef′s species richness index,Shannon-Wiener diversity index,Pielou′s evenness index.The relationships between abiotic environmental variables and nekton community pattern were investigated with gradient analysis,combining Monte Carlo test to determine limiting factors affecting nekton community structure of artificial reef zones.A total number of 18 fish species belonging to 15 families and 8 orders were collected during the surveys.Sebastes schlegeli,Hexagrammos otakii and Hexagrammos agrammus were the most abundant species.S.schlegeli was the absolutely dominant species in weight composition of catch(41%).The species number and catch of nekton at AR were higher than that at the control site,but the difference was not significant(P0.05).The highest average CPUE by season of investigation zones appeared in the reef zone near shore(NA) and reached 830.24 g/(net·d) during the surveys.It was noted that the parameters of community structure were highest in spring or autumn.However,no significant differences were found in community structure parameters between artificial reef zones and the control zones(P 0.05).Cluster analysis showed that similarities among quadrats of different zones were relatively high in spring,summer and winter,while similarities among quadrats between the reef and control zones off shore in autumn and all zones in spring were higher than those NA and control zones.37.1% of the variation in composition of nekton community was explained by water temperature in the RDA analysis,which suggested water temperature was main explanatory factor(Monte Carlo test P=0.002).The water temperature and depth were key environmental variables for temporal-spatial variation of nekton community structure in Lidao artificial reef zones.

A preliminary study on fish and macroinvertebrate enhancement in artificial reef area around Sanheng Isle, Shengsi, China

Fishes and macroinvertebrates(FM) were sampled respectively in ShangSanheng artificial reef area (marked by B) in May,Sept. of 2007 and Mar. ,May,Jul. of 2009 by trawl-net,and XiaSanheng artificial reef area(marked by A) from Jan. to Aug. of 2009 by multi-mesh gill-nets around Sanheng artificial reef waters,in order to assess resource enhancement effects of the deployed artificial reefs(ARs). Several control sites were chosen for better explanation on habitat restoration function by ARs. CPUE,Margalef species richness index,commercial species variation and Whilm species diversity index were used to discuss the change of FM resource. Result shows that:(1) A area: average CPUE’s significant differences were found neither between ARs and soft bottom habitat nor between ARs and rocky reef habitat(P 0. 05). However, the same index value from Feb. to Aug. between ARs and soft bottom habitat,was quite different(P 0. 05). Species richness level of ARs was obviously higher than that of the soft bottom habitat by 60. 2% (P 0. 05),no differences existed between ARs habitat and Rocky reef habitat(P 0. 05). Both ARs habitat and Rocky reef habitat share more commercial species than soft bottom habitat(P 0. 05),and they seemed to be equal by chance to attract commercial species(P 0. 05). As to species diversity,it was exactly the same as commercial species differences explained above,namely,which is equal between ARs habitat and Rocky reef habitat,and better than soft bottom habitat. (2) B area: CPUE in AR area was obviously improved by 2. 05 times after deployment(P 0. 05) and 2 times higher than that of control site(P 0. 05). Species richness level has been improved by 25. 3% after reef deployment,though no significant differences were found between them. However,it did have a better level than control site by 31. 3% higher(P 0. 05). 5 more commercial species were sampled in AR area after reef deployment compared to its original number(P 0. 05),and about 4 more species were sampled in AR area than control site after reefs were set. The diversity index in AR area has improved to a certain level,better than before and control site,though they appeared to be not so quite different(0. 05 P 0. 1). It is concluded that resource level and community structure have been improved a lot in both AR areas by comparison to its original level and control site level. The Sanheng artificial reefs have become a new habitat for more species and more individuals.

Seabird bycatch in Spanish Mediterranean large pelagic longline fisheries, 2000-2008

Incidental catch or bycatch represents a significant threat for the conservation of seabird populations. The western Mediterranean is an important fishing area where the Spanish pelagic and semi-pelagic longline fleet targeting swordfish (Xiphias gladius ), bluefin tuna (Thunnus thynnus ) and albacore (Thunnus alalunga ) operates. Bycatch of these fisheries includes several seabird species. Given the importance of conservation of the bycatch species (marine mammals, turtles, sharks and seabirds), an on-board observer program was implemented by the Spanish Oceanographic Institute (IEO); this included collecting data on effort and catch, as well as weight and number of individuals of the main bycatch species. The aim of the present study is to report data on seabird bycatch collected by the on-board observer program of the IEO in the Western Mediterranean. Data on seabird bycatch were collected for the period 2000-2008, throughout the year. Six longline gears targeting large pelagic fish were identified operating in the area of study, but only three had an effect on seabird species. Differences in catch per unit effort (CPUE, birds per 1000 hooks) for each gear, as well as their effect on particular seabird species, are reported in this study. A total of 4 786 466 hooks were monitored, which yielded 182 seabirds belonging to 7 different species. The average CPUE for the studied period was 0.038 birds per 1000 hooks. Cory’s shearwater (Calonectris diomedea ) and yellow-legged gull (Larus michahellis ) were the species the most highly represented in the catch. In contrast, Balearic shearwater (Puffinus mauretanicus ) was only present in the longline fishery targeting albacore (CPUE = 0.005 birds per 1000 hooks). Our results suggest that Cory’s shearwater is the species the most affected by the longline fishery in the Western Mediterranean, probably due to its biological characteristics, and corroborate the well-established downward trend in its population.

Mangrove oyster (Crassostrea spp.) (Sacco, 1897) extractivism in Cananéia estuary (São Paulo, Brazil) from 1999 to 2006: capture and management evaluation

The oyster Crassostrea spp. is one of the main fisheries resources in the southern portion of São Paulo State. This paper aims to evaluate the extractivism of that resource, supplying subsidies to the implementation of management regulations. This study was developed in Cananéia, from February 1999 to December 2006. The oyster production data in dozens was obtained through weekly or monthly interviews. The annual and average CPUE in dozens per day was analysis to verify significant differences along years. There are no regulations that limit the fishing effort or organize the admission in the fishermen. The admission is controlled by the condition of the market and there is a risk of increasing the fishing effort above the sustainable yield, which demands measures that control the number of fishermen engaged in the activity. Those measures, to be effective, must be created in discussion with the fisheries sector, based on technical information.

Assessing the potential of an artisanal fishing co-management in the Marine Protected Area of Torre Guaceto (southern Adriatic Sea, SE Italy)

In this study we investigated the potential of a fishing protocol adopted within the buffer zone of the Marine Protected Area of Torre Guaceto (SE Italy, Adriatic Sea) on fishing yields. The protocol, agreed with local fishermen and the MPA authority, aimed at regulating the fishing pressure within the MPA in the perspective to balance conservation and socio-economic needs. Fishing was completely banned in the entire MPA from 2001 to 2005. In 2005 fishing resumed within the buffer zone surrounding no-take zones. From 2005 to 2008 we monitored artisanal professional fishing (strictly exerted by trammel nets) within the buffer MPA, and compared CPUE (kg km −1 of net) with those obtained outside the MPA (where fishing grounds are fully open to professional and recreational fishing). Catches were higher inside than outside the MPA. Overall assemblage structures (evaluated on wet weight data) were significantly different from inside to outside the MPA, with the two most important commercial species, i.e. Mullus surmuletus and Scorpaena scrofa, accounting for ∼40% of the catch inside the MPA and ∼20% outside. In 2005, average CPUE within the MPA was about five-fold (∼50 kg km −1 of net) the mean value obtained outside. Such value then declined and tended to stabilize around 25 kg km −1 of net in 2007 and 2008. Average CPUE outside the MPA, instead, was ∼10 kg km −1 of net and remained quite stable across years. This study shows that the use of fishing co-management protocols within MPAs that properly involve local fishermen in the decision process is a promising approach to balance fishermen's and conservation needs.

Effect of bottom type on catch rates of North Sea cod ( Gadus morhua) in surveys with commercial fishing vessels

Seven surveys with commercial fishing vessels were conducted during a collaborative fishermen–scientist project on the distribution of cod in the north-eastern North Sea between June 2006 and June 2008. A flyshooter, a trawler and a gillnetter participated in this study. In general, catch rates were substantially higher on gravel or stone bottom and at ship wrecks than on sand bottom. The difference in the catch rates between the two bottom categories at paired stations within a short distance was highly significant for all the three fishing methods. Similarly, average CPUE for most surveys was several times higher on rough than on smooth bottom. These differences were highly significant for early autumn surveys conducted with the flyshooter and trawler and all gillnet surveys, the summer surveys for the flyshooter and the gillnetter, but not for the winter surveys with the trawler and the flyshooter. The latter suggest that bottom type preference may change with season, e.g. with respect to spawning migrations in winter and in relation with changes in the availability of food during spring and summer.

Mesoscale exploitation of a major tuna concentration in the Indian Ocean

The paper analyzes the daily catch, fishing effort and fish size data of the purse seine fleet fishing in the western Indian Ocean in February 2005, when a major concentration of tuna occurred and was heavily exploited by this surface fishery. This tuna concentration event occurred over a period of just 12 days, in an area of about 3500 square nautical miles located to the west of the Seychelles. This small stratum produced a total catch of 22 000 t, corresponding to 6.5% of the total fishing mortality of all adult yellowfin (Thunnus albacares) in the entire Indian Ocean in 2005. Sets were made mainly on free schools and the catch mainly composed of large yellowfin tuna. The average CPUE and the average catch per set were very large, 65 t and 85 t per fishing day, respectively. This “event” took place in a precise area where a high concentration of chlorophyll had been localized 18 days before. The subsequent concentration of tuna schools probably arose due to the high densities of their prey feeding on this large phytoplankton biomass. This phytoplankton bloom was observed at the edge of an anticyclonic eddy, but its origin and its high density cannot be fully explained by available environmental data. The adult yellowfin were probably at a reproductive stage and actively feeding on the local food chain generated by the phytoplankton bloom. Such an event is extreme, but typical of tuna purse seine fisheries where fleets often search for such tuna patches. These events play an important role in tuna fisheries due to the increase in fishing effort and fishing efficiency of purses seiners, both of which increase their impact on the resource. The fine scale study of such events and their improved integration into tuna stock assessments is recommended.

Contribution of Caridina nilotica (Roux) in the Dagaa Fishery in Lake Victoria, Tanzania

The contribution of Caridina nilotica in the Rastrineobola argentea (dagaa) fishery was assessed at nine beaches in the Tanzanian part of Lake Victoria from May, 2001 to April, 2002. Additional data on dagaa and Caridina catches from Sweya beach between October, 2000 and April, 2001 were also included. Two main methods are used to catch R. argentea and Caridina in the Tanzanian waters of Lake Victoria: mosquito seine nets (5 mm and 10 mm mesh sizes) and catamaran lift nets (8 mm mesh sizes). The majority of the beaches used mosquito seine nets as the main gear; lift net fishing was dominant at Igombe and Busekera beaches. Between May, 2001 and April, 2002, 157,390 t of dagaa were harvested in the Tanzanian waters of Lake Victoria; mosquito seine nets harvested 139,674 t (89%) compared with 17,716 t by lift nets (11%). CPUE was 244 and 337 kg boat− 1 day− 1 respectively for lift nets and mosquito seine nets. A total of 17,326 t of Caridina was harvested in the Tanzanian waters of Lake Victoria during the same period. More Caridina was harvested by mosquito seine nets (95%) than by lift nets (5%). Catch-per-unit-effort (CPUE; kg boat−1 day−1) for Caridina ranged between 1.87 and 45 kg boat−1 day−1, and varied with respect to location, time and fishing method. Sweya beach exhibited the highest CPUE and the lowest was at Nyangómbe beach. High CPUEs for Caridina were found during the rainy season at Sweya, Igombe, Kome and Busekera beaches. The rest of the beaches exhibited high CPUE during the dry season. CPUE of Caridina in lift nets was greater than in mosquito seines at Igombe and Busekera beaches. However, CPUE for dagaa at Igombe was higher for mosquito seines than lift nets. Reasons for these differences are unknown but probably relate to the location of fishing, particularly between inshore and offshore locations. Haplochromine cichlids were also abundant in the R. argentea catches at Igombe beach. The highest CPUE for haplochromines was at Igombe in January, 2002 and the lowest in June, 2001 (average CPUE for haplochromine cichlids at Igombe was 736 ± 746 kg boat−1 day−1 for lift nets). The total haplochromine catch for the region was estimated at 53,446 t. The carapace length (mm CL) distribution of Caridina in R. argentea commercial catches ranged between 1.5 mm CL and 8 mm CL depending on the gear used.

An observing system for the collection of fishery and oceanographic data

Abstract. Fishery Observing System (FOS) was developed as a first and basic step towards fish stock abundance nowcasting/forecasting within the framework of the EU research program Mediterranean Forecasting System: Toward an Environmental Prediction (MFSTEP). The study of the relationship between abundance and environmental parameters also represents a crucial point towards forecasting. Eight fishing vessels were progressively equipped with FOS instrumentation to collect fishery and oceanographic data. The vessels belonged to different harbours of the Central and Northern Adriatic Sea. For this pilot application, anchovy (Engraulis encrasicolus, L.) was chosen as the target species. Geo-referenced catch data, associated with in-situ temperature and depth, were the FOS products but other parameters were associated with catch data as well. MFSTEP numerical circulation models provide many of these data. In particular, salinity was extracted from re-analysis data of numerical circulation models. Satellite-derived sea surface temperature (SST) and chlorophyll were also used as independent variables. Catch and effort data were used to estimate an abundance index (CPUE – Catch per Unit of Effort). Considering that catch records were gathered by different fishing vessels with different technical characteristics and operating on different fish densities, a standardized value of CPUE was calculated. A spatial and temporal average CPUE map was obtained together with a monthly mean time series in order to characterise the variability of anchovy abundance during the period of observation (October 2003–August 2005). In order to study the relationship between abundance and oceanographic parameters, Generalized Additive Models (GAM) were used. Preliminary results revealed a complex scenario: the southern sector of the domain is characterised by a stronger relationship than the central and northern sector where the interactions between the environment and the anchovy distribution are hidden by a higher percentage of variability within the system which is still unexplained. GAM analysis showed that increasing the number of explanatory variables also increased the portion of variance explained by the model. Data exchange and interdisciplinary efforts will therefore be crucial for the success of this research activity.

Fisheries enhancement and biodiversity assessment of fish, prawn and mud crab in Chilika lagoon through hydrological intervention

The degraded state of the fragile ecosystem of Chilika lagoon on the east coast of India caused by natural changes and anthropogenic pressure was in the process of restoration through an effective hydrological intervention during 2000 after thorough scientific investigation including EIA study. The rich fisheries of Chilika lagoon that support livelihood of 0.2 million local fisherfolk was in dwindling state during the eco-degradation phase. Studies on fisheries and fish biodiversity of the lagoon for 4 years before and 4 years after the intervention showed the stark and rapid recovery of fishery immediately after opening of the new mouth with sixfold increase in average annual landing. The average productivity (11.3 t km−2) and CPUE (6.2 kg boat-day−1) during post intervention phase registered 528 and 464% increase, as compared to Pre-intervention years. In total, 277 species of fish and shell fish were documented as occurring in Chilika lagoon before the hydrological intervention. Inventory survey for fish and shell fish species diversity during and after hydrological intervention documented 68 and 97 species, respectively. New records of 56 species of fish and shell fish (7 freshwater, 20 brackishwater and 29 marine) were documented from Chilika lagoon after the hydrological intervention. Analysis of commercial catches showed that the migratory species contributed to the bulk of catches (75% by species and 68% by catch weight). Fish yield and biodiversity seemed to be very sensitive to salinity and hydrologic dynamics of the lagoon. Correlation analysis indicated inverse relationship between water transparency and fish catch (R 2 = 0.715; d.f. = 25; P < 0.01). Positive correlation between salinity and prawn landing (R 2 = 0.542; d.f. = 25; P < 0.01) and salinity and mud crab landing (R 2 = 0.628; d.f. = 25; P < 0.001). Average salinity for the whole lagoon was significantly increased by 42.7% (P < 0.007) as compared to pre-intervention situation. Maintenance of estuarine character of Chilika’s ecosystem particularly the salinity gradient, un-hindered auto-recruitment of fish and shell fish and prevention of destructive fishing are the key factors for fisheries enhancement. Unless carefully planned conservation and regulation measures are ensured with the active participation of local communities during the early phase of restoration, the present scenario of fisheries enhancement may not sustain for longer time.

Effects of fish density distribution and effort distribution on catchability

Abstract Ellis, N., and Wang, Y-G. 2007. Effects of fish density distribution and effort distribution on catchability – ICES Journal of Marine Science, 64, 178–191. The effects of fish density distribution and effort distribution on the overall catchability coefficient are examined. Emphasis is also on how aggregation and effort distribution interact to affect overall catch rate [catch per unit effort (cpue)]. In particular, it is proposed to evaluate three indices, the catchability index, the knowledge parameter, and the aggregation index, to describe the effectiveness of targeting and the effects on overall catchability in the stock area. Analytical expressions are provided so that these indices can easily be calculated. The average of the cpue calculated from small units where fishing is random is a better index for measuring the stock abundance. The overall cpue, the ratio of lumped catch and effort, together with the average cpue, can be used to assess the effectiveness of targeting. The proposed methods are applied to the commercial catch and effort data from the Australian northern prawn fishery. The indices are obtained assuming a power law for the effort distribution as an approximation of targeting during the fishing operation. Targeting increased catchability in some areas by 10%, which may have important implications on management advice.

Effort distribution and catch patterns adjacent to temperate MPAs

Abstract We evaluated the spatial distribution of otter trawl fishing effort and catches resulting from the imposition in 1994 of year-round and seasonal groundfish closed areas off the NE USA. Vessel locations were available from logbooks, vessel monitoring system (VMS) data from many of the largest vessels, and from observer records. There was high spatial coherence between VMS- and observer-derived trawling locations. Prior to establishment, 31% of trawl effort (1991–1993) occurred within the 22 000 km2 of area that would eventually be closed year-round. In 2001–2003 about 10% of effort targeting groundfish was deployed within 1 km of the marine protected area (MPA) boundaries, and about 25% within 5 km. Density gradients, consistent with spill-over from MPAs, were apparent for some species. Average revenue per hour trawled was about twice as high within 4 km of the boundary, than for more distant catches, but the catch variability was greater nearer closed area boundaries. Seasonal closed areas attracted more fishing effort after opening than prior to closure even while average cpue was the same or lower. Spatial resolution of traditional data sources (e.g., logbooks) was too crude to discern detailed MPA-related effects, as revealed by high-resolution vessel positions from VMS and catch data obtained by observers.

Fish Communities in Central Amazonian White- and Blackwater Floodplains

In Amazonian floodplains, the flood cycle of the river is becoming the dominant seasonal factor, and fish communities are found to fluctuate greatly over the year. During inundation, fish migrate into floodplain forests to feed on fruits and seeds, in an area more than 300 000 km2 in size. To document patterns of species diversity, distribution, abundance and temporal dynamics and in order to describe the ecological importance of the inundated forest, floodplain fish were captured using variously sized gill nets in white and black water areas inside and outside the floodplain forests during low, rising, high and falling water level in 1990 and 1991. Dominance varies to some extent in white water between floodplain forest (0.06) and open water (0.11) while it is unchanged in black water (0.04). Black water fish communities were more diverse. Most abundant among white water fish were Liposarcus pardalis, Pygocentrus nattereri, and Pellona flavipinnis, for example, or Plagioscion squamsissimus, Serrasalmus rhombeus, and Serrasalmus manueli in black water. Among the most abundant white water fish, Colossoma macropomum, Mylossoma duriventre and Osteoglossum bicirrhosum occurred almost exclusively in inundated forests. Of the black water species there were a large number of species which were captured only in inundated forest, such as Geophagus cf. altifrons, Hoplias malabaricus, Osteoglossum bicirrhosum and Uaru amphiacanthoides. Catches varied with sample site, water level and direction of water level change. The average CPUE in white and black water was 190 and 41 g fish m−2 and day, respectively, with maximum yields at low water and minimum yields at high water. Comparing rising and falling water levels, a significantly higher quantity of fishes was captured at falling water level. In black water, fish catches from the floodplain forest exceeded the open water catch by 183 to 550%, depending on season. Differences in respect of white water are smaller (106–281%). Fish communities in the area under investigation seem to be stochastically assembled, with significant differences between white and black water only. Many fishes move into the floodplain forest not only to feed but probably also for other reasons – to seek shelter, for example.

The recreational fishery for blue marlin, Makaira nigricans (Pisces: Istiophoridae), in the US Virgin Islands

Analyses of trends in the recreational fishery for blue marlin ( Makaira nigricans Lacepede) in the US Virgin Islands were conducted on data obtained from dockside sampling of sport fishing vessels. A total of 5729 blue marlin and 69 440 boat-hours of effort were recorded between the years 1983 and 1989. Annual catch per boat hour (CPUE) ranged from a low of 0.032 fish in 1985 to a high of 0.075 fish in 1987. About 97% of all blue marlin were caught between the months of June and October during the survey. The average CPUE for these months was 0.099 fish per boat-hour for the years 1984–1989 pooled. The proportion of fish boated has declined since 1983, while the proportion of fish tagged and released has increased during this same time period. In 1989, more than 96% of all blue marlin caught were tagged and released or released. This study has increased the knowledge of one Atlantic blue marlin fishery and has identified the Virgin Islands as one of the primary fishing locations for recreational blue marlin in the western North Atlantic.