Variation In Catch Research Articles

Effect of climatic oscillations on small pelagic fisheries and its economic profit in the Gulf of Cadiz

Several studies have shown the effect of climatic oscillations on fisheries. Small pelagic fish are of special global economic importance and very sensitive to fluctuations in the physical environment in which they live. The main goal of this study was to explore the relationship between the North Atlantic Oscillation (NAO), the East Atlantic pattern (EA), and the Arctic Oscillation (AO) on the landings and first sale prices of the most representative small pelagic commercial species of the purse-seine fisheries in the Gulf of Cadiz (North East Atlantic), the European anchovy Engraulis encrasicolus and the European sardine Sardine pilchardus. Generalised linear models (GLMs) with different data transformations and distribution errors were generated to analyse these relationships. The best results of the models were obtained by applying a moving average of order 3 to the dataset with a double weighted median. Our results demonstrate relationships between NAO, AO, and EA and European anchovy and sardine landings. These cause an indirect effect on the first sale price in markets through catch variations, which affect the price according to the law of supply and demand. The limitations of this study and management implications are discussed.

Türkiye’deki barbungiller balıkçılığının TÜİK mikro-veri setine dayalı olarak değerlendirilmesi

Although goatfishes (Mullidae Rafinesque, 1815) are among the most important commercial fishes in Turkey, no research has been found investigating the characteristics and spatial patterns of goatfish fishery. Here, we assessed the goatfish fishery of Turkey based on the microdata set of Turkish National Fishery Statistics gathered by Turkish Statistical Institute (TÜİK) between 2014 and 2017. In this context, we investigated the variation of total goatfish catch by cities. In addition, we compared the contribution of small (boat <10m) and large scale (boat >10m) fishers as well as different fishing techniques to the total goatfish catch in Turkey. Finally, an evaluation was made on the discard rates recorded in the official landing statistics. The results showed that higher red mullet (Mullus barbatus Linnaeus, 1758) catch was reported in the eastern Mediterranean, whereas surmullet (Mullus surmuletus Linnaeus, 1758) catch was significantly higher in the western Black Sea. On the other hand, fishery-independent investigations revealed that the Turkish fishery fleet mostly catches red mullet throughout the coasts of Turkey. Therefore, the separate records of red mullet and surmullet in the landing statistics likely represent the local names of red mullet rather than two different species. Large scale fishers were the main source of fishery pressure in the Mediterranean Sea, the Aegean Sea and the Black Sea. However, the majority of the catch was landed by small scale fishers in the Marmara Sea. The bottom trawl fishery landed 88, 92 and 87% of total goatfish catch in the Black Sea, the Aegean Sea and the Mediterranean Sea, respectively. Purse seiners provided the largest part of total goatfish catch (40%) in the Marmara Sea, where the bottom trawl fishery is prohibited. The overall average for the discard rate was found to be 0.47%. There were no statistically significant differences among the discard rates of two species, marine regions or fishing methods.

Temporal and regional variation in catch across an extensive coastal recreational fishery: Exploring the utility of survey methods to guide and assess spatio-temporal management initiatives.

As global research into recreational fishing gains momentum due to the pursuit’s biological, social and economic impacts, information on regional and temporal patterns of recreational exploitation will continue to enable objective assessment and development of management initiatives for exploited species. This paper demonstrates the utility of offsite survey methods in assessing spatial and temporal differences in recorded catches from a large, diffuse and heterogenous coastal recreational fishery. Using the estuarine recreational fishery that operates along the coast of New South Wales, Australia as a case study, survey data was employed to quantify annual (June 2013-May 2014) state-wide estuarine catch. Generalized linear mixed effects models were then applied to expanded catch estimates from surveyed households to examine the influence of zone and season on the kept and released numbers of snapper (Pagrus auratus), dusky flathead (Platycephalus fuscus) and bream (Acanthopagrus spp. complex comprised of A. butcheri, A. australis and their hybrids). For kept bream, significant differential seasonal effects were observed in all regions except the Mid-South Coast. For released bream, numbers were greatest in Sydney and during Summer and Winter. For kept snapper, the greatest harvest was recorded in the Mid-South Coast but season had no effect. Differential seasonal effects were found in each zone for released snapper. For kept dusky flathead, the greatest numbers were recorded in Sydney and the Mid-South Coast but season had no effect. We conclude by assessing some current spatial and temporal management initiatives in light of the uncovered patterns of recreational catch and consider the implications of these patterns in terms of future ecosystem-based management recommendations aimed at achieving ecological, social and economic sustainability in fisheries.

Spatial distribution and interannual variability of catches for pink salmon of artificial origin in the waters of eastern coast of Sakhalin Island in modern times

Mixed herds of pink salmon including the fish of both artificial and natural origin are exploited by fishery in many areas of Sakhalin Island. To separate the fish of different origin, large-scale tagging of the juveniles otoliths is conducted at salmon hatcheries since 2008. The hatcheries contribution to pink salmon catches in certain areas of East Sakhalin (from the Langeri River to Cape Crillon) is assessed for 2011–2017 on the base of previously published and new data on occurrence of the fish with marked otoliths. The specimens were sampled from commercial catches of 5–13 fixed nets and from research catches in 5–9 rivers throughout entire spawning season. In total, 40,992 otoliths of pink salmon were collected. The otoliths were prepared for microstructure analysis using standard methods of processing. All marked otoliths had the tags of hatcheries located on the eastern coast of Sakhalin. The fish of artificial origin were caught in all examined sites between Cape Soymonov and Cape Crillon every year, but in some years their distribution was wider, up to the northern limit of the investigated area (Langeri River). The fish of artificial origin migrated to all rivers within this area. The total annual landing of the pink salmon marked at artificial hatcheries in the East Sakhalin waters was estimated as 300–10600 t, by years. The rest of the fish of artificial origin (0.4–2.3 . 106 ind.) entered to the rivers and mostly reached the spawning grounds. Long-term dynamics of landing was compared for the pink salmon of artificial and natural origin and their independence was concluded. Distribution of pink salmon originated from certain artificial hatcheries by sites of catch was rather constant that allowed to extrapolate the results for marked fish to all released pink salmon. The highest contribution of pink salmon of artificial origin was noted for catches in the Aniva Bay (23.9 %, on average), it was lower for catches at the southeastern coast of Sakhalin (13.2 %), and more lower for catches in the Patience Bay (7.6 %). Total number of pink adults of artificial origin caught on a particular stretch of coast did not depend directly on the number of pink juveniles released from a local hatchery, but was determined mainly by number of fish migrated there from other hatcheries. The landing of pink salmon originated from artificial hatcheries directly in the rivers where these hatcheries were located and at their mouths was < 10 % of the total catch of pink salmon of artificial origin. Schemes of quantitative distribution of pink salmon with marked otoliths in the waters of East Sakhalin are presented.

Spatial pattern of fishing activities at Yogyakarta waters (case study: fishers at Depok beach, Parangtritis village, Bantul regency)

Capture fisheries are one form of fishery resource utilization by fisher in the waters. With open access, fishers are free to catch fish in the waters. Yogyakarta waters are one of the waters with capture fisheries activities that continue to develop until now, especially on Bantul Regency. Fishers on Depok Beach are the largest and most developed communities in Bantul Regency. Sustainable fisheries resource management is formed in Yogyakarta waters by analyzing fishers’ behavior on Depok Beach in fishing activities. Survey methods and participatory mapping were carried out to obtain fisher’s characteristics, water conditions, fishing grounds locations, and fish catch variation. Statistical descriptive analysis, map overlays, and correlations are used in this study. The fishing community on Depok Beach is dominated by migrant fisher who come from Cilacap. Fishing activities are still very dependent on water conditions both during high and low seasons. Fishing grounds can be up to 10 miles in the high season, while the low season tends to be closer to land. The type of fish catch varies each month, dominated by demersal fish. Beltfish (Trichiurus lepturus) is a fish caught commodity during high and low seasons. Meanwhile, white pomfret (Pampus argenteus), banana prawn (Penaeus merguiensis), scalloped spiny lobster (Panulirus homorus) are mostly found in the high season, and mackerel tuna (Euthynnus affinis) in the low season.

Long-Term Variability of Piscivorous Fish in China Seas Under Climate Change With Implication for Fisheries Management

Due to persistent fishing expansion in the China Seas over the past six decades, fisheries resources have been over-exploited; as a result, exploited fish have become smaller in size and younger in age. Marine piscivorous fish constituted a large portion of Chinese fisheries catch, long-term variability of which has rarely been investigated despite intense fishing pressure and climate change. In this study, we attempt to identify their responses to climate change and fishing activities and to provide scientific basis for sustainable exploitation of these resources. Seven taxa from pelagic to demersal species inhabiting either cold-water or warm-water were selected to represent the piscivorous fish assemblage in the China Seas. Total catch of these piscivorous fish in the China Seas increased during the early 1990s, stabilizing around 1.2 million tons after 1997. Principal component analysis (PCA) showed evident interannual-decadal variabilities in the catch of these fish with step changes around 1985/86 and 1997/98. Individual taxa, however, showed different trends in catches with sharks, rays, and lizardfishes manifesting downward trends while Pacific cod, eels, and hairtail increasing. Common dolphinfish and Japanese-Spanish mackerel increased largely in the 1990s but declined slightly during the 2000s. Although there were temporal overlaps between climate change and fishing variabilities, results of gradient forest analyses indicated that fishing effort imposed the most important influence on piscivorous fish. And among all climate variables explored in this study, sea surface temperature (SST) especially that of the East China Sea, had greatest impacts on variations in piscivorous fish catch, which may have been gradually exacerbated by the continued high fishing intensity. In addition, significant changes were identified in the life history traits in the species we evaluated, such as reduced average body sizes and truncated age compositions, strongly indicating the effect of fishing. We therefore advocate precautionary fishery practices under climate change.

Indexing Reservoir Channel Catfish Population Density and Size Structure with Tandem, Baited Hoop Nets

AbstractFisheries managers efficiently sample reservoir Channel Catfish Ictalurus punctatus populations with tandem, baited hoop nets. However, catchability (the fraction of a fish stock caught with a defined unit of effort) of Channel Catfish with this gear and the size selectivity of this gear are not fully known. Furthermore, scientists have not identified a standard sampling period that maximizes catches while minimizing variation in catchability. Here, we estimated Channel Catfish population density (number/ha) and catchability with tandem, baited hoop nets using mark–recapture methods in three Ohio reservoirs during May–July 2016–2018. We tested for differences in catchability (1) among reservoirs; (2) among 50‐mm length categories; and (3) by week. We then tested CPUE as an index of density by simulating the sampling of populations with different densities based on observed variation in catchability and estimating the statistical power to detect density differences. We found that total catchability differed among study reservoirs, among length categories, and among sampling events but did not consistently change during the May–July sampling period. Catchability of 50‐mm length categories did not differ among reservoirs. The greatest catchability was observed for 400–649‐mm Channel Catfish. Our power analysis showed that we could detect a large (>2:1 effect sizes) difference in density with 80% power by using 20 or more sample sites. Furthermore, our length‐category‐specific catchability estimates provide information to reduce bias in size structure, growth, and mortality estimates derived from Channel Catfish samples collected with tandem, baited hoop nets. We encourage further development, validation, and application of tandem, baited hoop nets to better understand differences in reservoir Channel Catfish densities and size structures.

Spatial Distribution of Lift Net (bagan) and The Impact on Sardinella lemuru Catches in Senggrong Bay, Banyuwangi

The spatial distribution of lift net (bagan) and the impact on the Sardinella lemuru (lemuru) catches in Senggrong bay - Banyuwangi has been analysed. The data used in this study consists of Pleiades satellite data, aerial photographs of unmanned aerial vehicle (UAV) or drones and in situ measurements in the same period. Fishery data during 2013 to 2017 were analysed to determine the variability of Lemuru catches. The analysis of bagan spatial distribution was performed using visual interpretation technique. Spatial distribution of bagan was analyzed by overlaying data at different period. The results show that the number of bagan in Senggrong bay were 85 unit and spread evenly throughout the bay. In the northwest monsoon, the bagan were spreadedin the northern part of the bay, while in the southeast monsoon, the bagan were shifted to the south due to the high waves and wind speed. Lemuru spawning time was occured in May – July. During spawning time, the amount of Lemuru catches by bagan was relatively low. The peak of lemuru catch was occurred in the period of October to January. The impact of bagan on the decreasing of lemuru abundance is relatively low.

The role of oceanic environmental conditions on catch of Sardinella spp. in Ghana

Fish stock distribution is greatly influenced by oceanographic environmental conditions. Temporal variations of temperature and other oceanic properties, resulting from climate change have been documented to have a strong impact on fisheries and aquaculture. In Ghana, Sardinella species are one of the most important fisheries resources; they constitute about 60% of the total catch of coastal fisheries and are more predominant during the upwelling season. The present study investigated the role of physical oceanographic environmental conditions in the catches of Sardinella species: S. aurita and S. maderensis, which were landed in Ghana. Furthermore, we examined the relationship between environmental conditions and catches of Sardinella species for seasonal and interannual variations between 2005 and 2015. For oceanographic environmental factors, we used comprehensive datasets, which consist of :(1) daily in situ SST data obtained at two coastal stations in Ghana; (i) Cape 3 Points (4.7° N, -2.09° W) and (ii) Tema (5° N, 0° E), for the period 2005–2015, (2) Monthly SST data (MOAA GPV) from JAMSTEC, and (3) gridded 10 meter wind data from CCMP reanalysis. The analysis of the data collected showed that higher (lower) wind velocity forms stronger (weaker) coastal upwelling that is detected by lower (higher) SST, resulting in a higher (lower) catch of Sardinella spp., in both seasonal and interannual variations. It was also observed that the capture ability of small pelagic fish species such as Sardinella spp. is depend on the intensity of the coastal upwelling. Moreso, the Atlantic Meridional Mode index (climatic index) is now known to be a possible factor to the interannual variation in catch of small pelagic fish species.

Assessing the spatial distribution of five non-commercial fish species in the Aegean Sea (Greece, eastern Mediterranean Sea) based on discards data

Spatial management of discards has attracted increasing interest as a potential mitigation measure. However, most studies are restricted to commercial species. The aim of the present work was to fill this gap by identifying and mapping the spatial distribution of five non-commercial species with high frequency of occurrence in the discarded catch of bottom trawl fishery in the Aegean Sea, i.e., Brown comber Serranus hepatus, Mediterranean scaldfish Arnoglossus laterna, Red bandfish Cepola macrophthalma, Argentine Argentina sphyraena, and Boarfish Capros aper. For this purpose, Generalized Additive Models were used to account for catch dependency on environmental parameters in order to explore the spatial distribution of species. Modeling results revealed that the spatial distribution of species was driven by environmental variables. Depth was the most informative variable explaining most catch variation in all species. For A. laterna, C. macrophthalma, and S. hepatus the highest estimated values of catch were located over the continental shelf and at shallower waters inside gulfs, whereas C. aper and A. sphyraena catch were more broadly distributed across the study area and at greater depths. Seasonal variations in species catch were also observed, probably related in most cases to species reproduction period. Mapping species distribution is essential for the identification of priority areas of protection in future marine spatial plans.

Variability of mackerel fish catch and remotely-sensed biophysical controls in the eastern Pemba Channel

Advances in satellite remote sensing of environmental perturbations have become important in understanding variations of ocean productivity and small pelagic fish catches. This marine resource is vital for coastal populations dependent on artisanal fishing for their income and food security, such as in coastal East Africa. In this region, the eastern Pemba Channel (Tanzania) represents a hotspot area, for a variety of marine species including small pelagics and coral reef associated species. This study examines the links between mackerel fish catch, one of the important small pelagic fish for direct consumption in the region, and changes in environmental oceanographic parameters over the period 2012–2018. The fisheries catch data is a rare local dataset, consisting of daily mackerel landings (from 2012 onwards) and supplemented by qualitative information on the mackerel fishery obtained through interviews with local stakeholders. The physical factors influencing phytoplankton biomass, and in turn, mackerel fisheries yield is investigated, using remotely-sensed chlorophyll-a (Chl-a) and Sea Surface Temperature (SST), together with Mixed Layer Depth (MLD) data from the high-resolution ocean model NEMO. We show that seasonal variations in mackerel landings are positively (negatively) correlated with Chl-a (SST) with a 1-month time lag (i.e., biophysical factors change first, mackerel stocks follow one month later). On the eastern side of the Pemba Channel, cooler SST and higher Chl-a are observed during the Southeast monsoon accompanied by increased mackerel landings, suggestive of enhanced productivity. Interannually, these relationships remain valid both for monthly and annual means, which confirms the close link between the variations of mackerel and biophysical conditions. Analysis of the Chl-a and MLD anomalies, relative to the mean, reveals that the phytoplankton blooms observed on the eastern side of the Pemba Channel, during the Southeast monsoon, are likely due to the deepening of the mixed layer, which tends to entrain cold and nutrient rich waters from greater depths to the surface. We conclude that upper ocean mixing contributes to the observed enhanced productivity along with other environmental factors. Additionally, we show how our results can be applied in the management of the mackerel resource in the Pemba Channel.

Eastward Expansion of Round Goby in New York: Assessment of Detection Methods and Current Range

AbstractThe Round Goby Neogobius melanostomus has spread rapidly around the Great Lakes region since its introduction to North America in 1990. In 2014, a specimen was captured in the New York State Canal System west of Utica, prompting concerns that Round Goby would soon reach the ecologically and economically valuable watersheds of Lake Champlain and the Hudson River estuary. The establishment of Round Goby populations elsewhere has been linked to a number of negative ecological consequences, yet methods for monitoring the invasion front of this species remain limited. The objectives of this study were to assess the current distribution of Round Goby in central New York and to determine the most effective methods for monitoring the invasion front. This was achieved by concurrently using benthic trawling, seining, minnow traps, and environmental DNA (eDNA) twice annually from 2016 to 2019 at 12 sites on the canal system between Oneida Lake and the Hudson River. Of the three traditional gear types, benthic trawling was the most effective method and captured Round Goby as far east as Utica by 2019. This finding suggests only minimal eastward expansion of Round Goby occurred between 2014 and 2019. Round Goby DNA was detected in water samples during all surveys in which individuals were captured with trawling, and the estimated concentration of DNA explained 69% of the variability in trawl catch. At multiple study sites, Round Goby DNA was identified during consecutive surveys before Round Goby were first captured with trawling. This suggests that in lotic waters, eDNA has the potential to forecast or serve as a sentinel for the expansion of Round Goby to new locations. Our results demonstrate the importance of using eDNA in a repeated sampling framework and supplementing eDNA sampling with some level of effort with traditional sampling methods.

Species composition and variation of catches by a set net in the coastal waters of Sinsan, Jeju Island

Species composition and variation of catches by a set net in the coastal waters of Sinsan, Jeju Island

A model-based approach to standardizing American lobster (Homarus americanus) ventless trap abundance indices

Fishery-independent ventless trap surveys are an integral component to assessing American lobster (Homarus americanus) population trends, as they can sample complex, heavily fished habitats where most survey gear has difficulty accessing. U.S. American lobster stocks have been assessed within state waters using a standardized ventless trap survey since 2006. However, confounding survey attributes that may contribute to catch variability have not been investigated and some discontinuity in sampling has resulted in missing estimates of abundance. We constructed sex- and stock-specific generalized linear mixed models to discern the dynamics between lobster catch and individual survey factors and removed these sources of variability when producing continuous abundance indices. Soak time, day of year, and unique site had measurable contributions to the variability in lobster catch per ventless trap. Generally, sex- and stock-specific abundance indices from this model-based approach and a traditional design-based approach exhibited similar trends. The two approaches’ magnitudes and trends for the Gulf of Maine were nearly identical. For Southern New England, model-based index trends were smoother and lower in magnitude than the design-based estimates. The greatest difference in the two approaches’ trends for the Southern New England indices were in the early and terminal years. This work serves as an example of how variability associated with fixed and random effects of a survey can be accounted for when producing abundance indices used in stock assessments.

Catch-effort model used as a management tool in exploited populations: Wild boar as a case study

For sustainable management of exploited populations, it is required to have good knowledge on temporal trends in population density to adapt the harvest. In this regard, hunting statistics are often collected routinely by government agencies and associations. These data are used to assess demographic trends through the development of indices, which are in turn used to manage exploited populations in a sustainable way. However, these population indices depend on features of the hunting process (e.g. hunting effort, hunting conditions, probability of catch). In this study, we show how to use hunting logs to assess demographic trends in exploited populations while accounting for the components of the hunting process. In particular, we developed a catch-effort model to study how the hunting effort leads to mortality rate – hunting pressure – within a given habitat type and during a given period. We illustrated the usefulness of this approach using exploited wild boar (Sus scrofa) populations as a case study. We used a large hunting logs dataset to perform our study, with several hundreds of thousands hunting events for more than 10 years in two French departments in France, including information about the number of hunters, of wild boars culled and the date of the hunt. We showed that catchability is a key parameter to assess hunting pressure at a given time and place. This parameter varies both within the hunting season and between habitat types. Once this variation in catchability was accounted for, our catch-effort model allowed us to obtain estimates of relative densities of wild boar populations over the study period at the management unit scale. Thus, catch-effort models are powerful tools to assess population density and to understand the underlying hunting process. Our study offers straightforward and reproducible conceptual framework that can be applied routinely by wildlife managers on exploited populations and practitioners from hunting statistics logs.

Annual variation in condition factor of sand lance Ammodytes japonicus during the estivation period in Harima-Nada, eastern Seto Inland Sea, Japan

The sand lance Ammodytes japonicus has been one of the most important fisheries resources in the eastern Seto Inland Sea, but long-term variations in annual catch have shown a decreasing trend. This species estivates for about 5 -months and does not eat during the period in Harima-Nada, eastern Seto Inland Sea. Therefore, a sufficient condition factor is important to survive the estivation period and start maturity thereafter. In this study, we investigated the condition factor of age-0 fish, which account for most of the catch, during the estivation period (July–November) together with water temperature in Harima-Nada from 2010 to 2017. The mean condition factor of the age-0 fish in late July ranged from 3.76 to 4.55 and decreased each month to values in late November from 2.91 to 3.59. The reduction rate (%) of the condition factor varied from 15.5% to 26.6%. The slopes of the decreasing condition factor, which were calculated from the relationship between the monthly condition factor of individuals and Julian Days each year, showed no significant correlation with cumulative water temperature from the first sampling day in July to the last one in November. The condition factor of sand lance was generally maintained at the end of the estivation period if the condition factor was high at the beginning of the period. The results suggest that starting estivation with a high condition factor is the most important criterion to enable survival of sand lance in Harima-Nada.

Catch Variations of Argentine Shortfin Squid Illex argentinus in the Southwest Atlantic

Catch Variations of Argentine Shortfin Squid Illex argentinus in the Southwest Atlantic

Diel variability in catches of major bottom-dwelling fish species in the southwestern part of the Sea of Japan

Diel variability in catches of major bottom-dwelling fish species in the southwestern part of the Sea of Japan

Long-term spatiotemporal variation in Miyazaki Prefecture coastal fishery catch in relationship to oceanographic conditions

Long-term spatiotemporal variation in Miyazaki Prefecture coastal fishery catch in relationship to oceanographic conditions

Factors of long-term variation in the fishery catch of red sea bream in Miyazaki Prefecture

Factors of long-term variation in the fishery catch of red sea bream in Miyazaki Prefecture