Fyke Nets Research Articles

Population Viability Analysis of Kinosternon hirtipes murrayi in Central México, with Notes on the Conservation Status of the Other Three Subspecies of the Lineage

With 6 subspecies described, the rough-footed mud turtle (Kinosternon hirtipes) has been considered a species with high morphological diversity. One subspecies, K. h. megacephalum, is already extinct. The remaining subspecies are poorly studied, with very limited information available only for K. h. murrayi (a widespread subspecies). The remaining taxa (K. h. tarascense, K. h. chapalense, K. h. magdalense, and K. h. hirtipes) are microendemic and restricted to endorheic valleys in the Mexican Transvolcanic Belt. Using baited fyke nets, hoop traps, and a seine, we surveyed for these microendemic subspecies for 3 yrs across their known distributions. With the data gathered in the field and published information, we conducted a population viability analysis (PVA) to model the minimum characteristics needed to improve population growth under 3 scenarios (optimistic, intermediate, and pessimistic). Very few K. hirtipes turtles were collected. No K. h. chapalense were located in Lake Chapala, but we did capture 4 individuals in Lake Zapotlan. Similarly, only 6 individuals of K. h. magdalense were captured. No K. h. hirtipes individuals were collected in the Valley of México. Two populations of K. h. tarascense were located in the Pátzcuaro basin: the first populations reported for that subspecies. The PVA showed that harvest on adults in populations with fewer than 200 turtles significantly compromises population persistence. However, a population size of 200 and limited or no harvest are enough to increase population size and persistence for at least 100 yrs. Assurance colonies and head-starting may be the only chance for long-term survival of some of these microendemic turtle lineages.

EDNA metabarcoding outperforms traditional fisheries sampling and reveals fine‐scale heterogeneity in a temperate freshwater lake

AbstractUnderstanding biodiversity in aquatic systems is critical to ecological research and conservation efforts, but accurately measuring species richness using traditional methods can be challenging. Environmental DNA (eDNA) metabarcoding, which uses high‐throughput sequencing and universal primers to amplify DNA from multiple species present in an environmental sample, has shown great promise for augmenting results from traditional sampling to characterize fish communities in aquatic systems. Few studies, however, have compared exhaustive traditional sampling with eDNA metabarcoding of corresponding water samples at a small spatial scale. We intensively sampled Boardman Lake (1.4 km2) in Michigan, USA, from May to June in 2019 using gill and fyke nets and paired each net set with lake water samples collected in triplicate. We analyzed water samples using eDNA metabarcoding with 12S and 16S fish‐specific primers and compared estimates of fish diversity among methods. In total, we set 60 nets and analyzed 180 1 L lake water samples. We captured a total of 12 fish species in our traditional gear and detected 40 taxa in the eDNA water samples, which included all the species observed in nets. The 12S and 16S assays detected a comparable number of taxa, but taxonomic resolution varied between the two genes. In our traditional gear, there was a clear difference in the species selectivity between the two net types, and there were several species commonly detected in the eDNA samples that were not captured in nets. Finally, we detected spatial heterogeneity in fish community composition across relatively small scales in Boardman Lake with eDNA metabarcoding, but not with traditional sampling. Our results demonstrated that eDNA metabarcoding was substantially more efficient than traditional gear for estimating community composition, highlighting the utility of eDNA metabarcoding for assessing species diversity and informing management and conservation.

Submerged Aquatic Vegetation Patch Size Affects Fish Communities in a Turbid-Algal Lake

Submerged aquatic vegetation (SAV) is declining worldwide, leading to subsequent reductions in the ecological functions associated with SAV in shallow aquatic ecosystems, including providing habitat for fishes. Extensive restoration efforts are required to reverse this trend, but studies focusing on aquatic vegetation have been uncommon in recent years relative to other primary producers. Evaluations of the most beneficial SAV species and characteristics for fishes are especially rare. Because of the potentially complex and inconsistent responses of fish to different management actions, further research is necessary to evaluate the species-specific and community-level effects of SAV to inform restoration decision-making. To examine what SAV characteristics increase fish habitat use in a turbid-algal lake undergoing restoration, we sampled 29 areas around Lake Apopka, Florida (USA) with fyke nets and trotlines. We examined the impact of eight environmental variables on fish abundance, biomass, community structure, and predation potential. For each approximated 0.6 m2increase in SAV patch size, total fish biomass catch increased 6.5 g hr−1. Fish community composition based on abundance also changed with an increase in SAV patch size. The number of bait items missing from trotlines, a measure of predation potential, was most affected by water temperature, wind speed, and time of day, but not by the SAV variables tested. These results expand existing knowledge of fish habitat use of SAV and will inform future management efforts to conserve and restore fish communities by focusing on specific SAV characteristics such as patch size.

Acoustic camera and net surveys reveal that nursery enhancement at living shorelines may be restricted to the marsh platform

Rapid human development in coastal areas is introducing significant amounts of novel habitat and leading to widespread habitat simplification. To predict how species will respond to these changes, it is important to understand how organisms interact with novel habitats versus naturally existing habitats. In this study, we used traditional fish sampling gear (fyke nets and minnow traps) and a Dual-Frequency Identification Sonar (DIDSON) to conduct fish surveys along natural and modified estuarine shorelines in North Carolina, USA. The overall objective of our study was to investigate how fish abundance and other community metrics change as a function of shoreline type (natural marsh, living shoreline, or bulkhead), sampling location (marsh platform or the shallow subtidal area offshore of the structure), and time of day (day or night). Using fyke nets, we caught significantly more fish and recorded higher species richness on the marsh platform at living shorelines versus natural marsh shorelines. However, we found no significant differences in fish abundance in the shallow unvegetated habitats seaward of the different shoreline types, which may have been affected by low sampling efficiency and replication when sampled using minnow traps and the DIDSON. Our findings, in conjunction with similar studies, may reflect a localized shoreline effect where the nursery enhancement observed at living shoreline sites is restricted to the living component of the shoreline (i.e., the marsh). Additionally, the preliminary results from our limited daytime versus nighttime DIDSON sampling show no significant differences in fish detections. This contrasts with many previous studies using traditional fish sampling techniques that report substantially higher fish catches at night. This unexpected finding is worthy of additional research as it may suggest that traditional fish sampling techniques are underestimating fish abundances during the day, perhaps due to visual gear avoidance. Ultimately, a careful consideration of the social and ecological goals of any shoreline stabilization project is needed before choosing a final design; however, maximizing habitat restoration and limiting the use of artificial materials is likely to confer the greatest ecological benefit.

Düğümlü ağdan donanmış geleneksel kerevit pinteri ile alternatif olarak düğümsüz ağdan donanmış pinterlerin CPUE karşılaştırması

In this study, it is aimed to compare the yield and strength of the crayfish fyke rigged with knotless net with 210d/12 rope thickness with those of the traditional net material rigged with 210d/6 knotted net which is widely used in Turkey in fishing crayfish (Pontastacus leptodactylus, Eschscholtz, 1823). The study was carried out on a monthly basis between June 2017 and May 2018. In the study, a total of 300 fyke nets, equipped with 150 classical and 150 alternative nets, were used. The caught crayfishes were measured and weighted according to the fyke net they were caught in. A total of 3509 crayfish were caught, 1465 of which were caught with alternative fyke net and 2044 with traditional fyke net. Average CPUE value ranged from 10.93 (g/fyke net/day) to 281.14 (g/fyke net/day) for per fishing operation. Average CPUE value of the traditional gear was found to be 98.34 (g/fyke net/day) , while that of the alternative gear was determined as 79.46 (g/fyke net/day), and no statistically significant difference was found between average CPUE values (p>0.05). Average strength value of the traditional fyke net was determined as (± SE) 10.43 ± 0.27 kg, while that value in 210d / 12 knotless net was identified as 14.50 ± 0.91 kg (p<0.05). Although it has high strength, since the CPUE value of the alternative fyke net is lower by 19.20% compared to the traditional gear, it is believed that its use in crayfish fishing will not be profitable.

Status of the fishery of Jaffna lagoon, Sri Lanka

Jaffna lagoon (9° 50' N and 79° 50' E to 9°20' N and 80° 30' E) is the largest lagoon in Sri Lanka and it provides many services including fishing opportunities to the people in northern Sri Lanka. However, the status of the Jaffna lagoon fishery is not fully known at present due to the lack of detailed studies over the last 40 years. Therefore, this study was designed to fulfil this research gap. Both primary data and secondary data were used in this study. Primary data, including catch and fishing effort were collected at three major landing sites, Gurunagar, Paasaiyoor, and Kachchai by making fortnight field visits from March to December 2019. Secondary data of the monthly total catch and fishing effort were obtained from the district fisheries offices in Jaffna and Kilinochchi districts in order to estimate MSY and FMSY. This study revealed that ~5340 fishers confined to 39 landing sites were actively engaged in lagoon fishing during the study period using 12 different fishing methods. Fyke nets (71%) followed by stake nets (10%), lagoon seines, and lagoon boat seines (6%) are the widely used fishing methods in lagoon fisheries. Catch rates of major fishing gear were calculated and recorded as kg fisherman-1, day-1. Stake net (37kg ± 7) reported a significantly higher catch rate than fyke net (18kg ± 3), seine net (17kg ± 6), and crab net (16kg ± 3) (p<0.05; ANOVA). Both mechanized (59%) and non-mechanized (41%) crafts are used in the lagoon fishing practices. Forty-six commercially important finfish and shellfish species belonging to 25 families were identified in the lagoon catches of which Penaeidae made the highest percentage contribution (27%), followed by Siganidae (13%), Mugilidae (11%), Lethrinidae (10%), and Gerreidae (9%). Analysis of secondary data confirmed the increasing trend of fishing effort since 2009 but the total landings declined gradually after reporting its maximum value of 6958 Mt. in 2012. A rough estimate of maximum sustainable yield of the fishery of Jaffna lagoon was 6,694 Mt with the annual fishing effort (FMSY) of 1007 crafts. As the current fishing effort is higher than the FMSY, input control measures are recommended to utilize the lagoon fishery resources in a sustainable manner.

101 lakes - lentic fish community monitoring using eDNA metabarcoding

We have recently developed and deployed methods for environmental DNA (eDNA) based monitoring of lake fish communities in the UK. This approach combines eDNA with modern High-Throughput-Sequencing technology, so-called eDNA metabarcoding. This non-invasive method has proven to be more effective at detecting elusive species than established invasive surveying techniques such as electro fishing or fyke netting and can provide meaningful semi-quantitative abundance estimates. The UK Environment Agencies have funded the collection of an eDNA meta-barcoding data set of vertebrates from 101 UK lakes covering a broad spectrum of environmental conditions Fig. 1. This dataset is based on analysing 20 water samples per lake and has successfully been used to develop a WFD compatible water quality assessment tool. In its current form this tool is suitable for reporting the status of fish in water bodies where eutrophication is the dominant pressure. DNA is not homogeneously distributed in lentic environments and hence the detection of species relies on the collection of an adequate number of samples from a water body to capture the eDNA signal. Previous analyses on a subset of lakes have indicated that the number of samples used for the 101 lake fish data set is more than sufficient to reliably estimate species richness of lakes, but it is unclear how exactly reduced sampling effort affects other biodiversity estimates and inferences made about water quality. As the number of samples determines the cost of monitoring programmes it is essential that the sampling effort is optimised for a specific monitoring objective. The objective of this study was to explore the effect a reduced sampling effort would have on various biological inferences using algorithmic and statistical resampling techniques. with a much lower number of samples. For example, almost 90% of lakes achieved a sample coverage of 95% with only 10 samples. However, rare species are more often missed with fewer samples, with implications for monitoring programs of invasive or endangered species. Estimates of community composition and the ecological quality ratio (EQR) responded slowly to decreasing sampling effort. For example, subsets of 10 samples were in most cases much more closely related to each other than to sample sets from other lakes and showed very similar Ecological Quality Ratios. These results are able to inform the design of eDNA sampling strategies, so that these can be optimised to achieve specific monitoring goals.

Fish Response to Multiple Anthropogenic Stressors in Mediterranean Coastal Lagoons: A Comparative Study of the Role of Different Management Strategies

Transitional waters are among the most productive ecosystems of the world and their biotic communities show high diversity and complex mechanisms of self-regulation that provide valuable ecosystem services and societal goods and benefits. In this work a comparison of the fish assemblages of three non-tidal Mediterranean coastal lagoons is carried out in order to evaluate the impacts of alternative management strategies. The anthropogenic pressures acting on the lagoons were quantified by means of categorical indicators, while the characteristics of the fish assemblages were summarized in multi-metric indices (MMIs). Two MMIs were developed using data collected with a beach seine net and with fyke nets, following an empirical approach that selects, from a pool of 73 metrics, the combination that maximizes the MMI/pressure relationship. The two MMIs include four metrics each, most of which are based on feeding mode functional guilds and habitat use functional guilds, and they are sensitive to anthropogenic pressures. The human activities directly or indirectly affecting water quality are the ones that most influence the fish assemblage, while the presence of artisanal fisheries, a typical and relevant resource use in these lagoons, seems to play a beneficial role. Lagoon fisheries management relies on the maintenance of infrastructures that guarantee the hydraulic functioning of the lagoon, thus ensuring exchanges with the adjacent coastal sea, and therefore indirectly contributing to the habitat quality.

Native and non-native fish across aquatic habitats in the Ebro Delta

We describe the variability in the composition of fish communities in the Ebro Delta (NE Iberian Peninsula) and report the habitat preferences of the most common species. The Ebro Delta is a large coastal wetland that has been intensively modified, mainly for rice cultivation involving the input of a large amount of low-conductivity waters into an originally brackish and saline system. We de- fined nine main habitat types within the Ebro Delta (the river, inflow channels, rice fields, outflow channels, springs, marshes, lagoons, lagoon mouths and bays) and sampled fish communities in them by establishing 376 sampling sites, in which we set 1431 fyke nets. We captured more than 120,000 fish belonging to 52 species, of which 37 were native and 15 were non-native. The ichthyofauna of the Ebro Delta is strongly structured in relation to habitat type, following variations in water salinity, and there is a clear segregation of native and non-native fish species. Native species are clearly dominant in the more saline habitats, namely bays, lagoons, lagoon mouths and marshes, while non-natives dominate the aquatic habitats related to rice cultivation (inflow and outflow channels as well as rice fields). Freshwater springs are dominated by non-natives in terms of abundance, but not in terms of richness. Since the decline and loss of native fish species in the Ebro Delta seems linked to the massive inflow of low- conductivity waters for rice irrigation, fish conservation must focus in reducing the influence of those outflows on the remaining natural and semi-natural wetlands.

Ecology of Riverine Turtle Communities in the Southern United States: Food Resource Use and Trophic Niche Dimensions

As part of an integrated study of the ecology of freshwater riverine turtle communities in the southern United States, we analyzed food resource partitioning in the turtle communities of the Cahaba, Chickasawhay, and Pearl rivers. We collected turtles with an array of unbaited fyke nets for periods of 10 d from 1 July to 13 August 1978 and 30 April to 4 August 1979, capturing 2707 turtles of 16 species in 2428 trap days. We successfully flushed the stomach contents from 729 turtles of the following species: Apalone mutica, Apalone spinifera, Graptemys flavimaculata, Graptemys gibbonsi, Graptemys nigrinoda, Graptemys oculifera, Graptemys pearlensis, Graptemys pulchra, Pseudemys concinna, Sternotherus carinatus, Sternotherus peltifer, and Trachemys scripta. We also caught 4 other species in low numbers: Chelydra serpentina, Graptemys pseudogeographica kohnii, Macrochelys temminckii, and Sternotherus odoratus. Stomach contents were identified and quantified by volume and percentage of occurrence for each species from each river. Food items were identified and placed in 6 categories: crustaceans, insects, mollusks, fish, plants, and unidentified. Pseudemys concinna was the most specialized feeder at all 3 sites, feeding almost exclusively on plants, followed by the wide-headed Graptemys and then narrow-headed Graptemys. Specialist species tended to show extensive niche overlap with any other species that consumed a large proportion of the specialists' preferred foods.

A Comparison of Two Methods for Sampling Bluegill and Redear Sunfish in Small Impoundments

AbstractBluegill Lepomis macrochirus and Redear Sunfish L. microlophus are highly regarded recreational species throughout North America. Management of these species relies on sampling methods that accurately and efficiently describe population characteristics of the target population. Largemouth Bass Micropterus salmoides and crappies Pomoxis spp. are commonly sampled with spring electrofishing and fall fyke netting, respectively. If lepomids can be effectively sampled concurrently with Largemouth Bass or crappies with one of these sampling methods, it would improve sampling efficiency in small impoundments. Our objective was to compare two sampling methods (North American standard fyke netting and electrofishing) for sampling Bluegill and Redear Sunfish populations in small impoundments by comparing size structure, sampling precision (relative standard error), and sampling efficiency (effort needed to collect 125 stock‐length fish). Typically, spring electrofishing caught a wider size range of Bluegill and Redear Sunfish than fyke nets, but proportional size distribution was similar between gears. However, length frequencies differed between gears in all impoundments for Bluegill and in three of five impoundments for Redear Sunfish. Electrofishing typically caught a greater proportion of large lepomids than fyke nets in those cases, though the differences were subtle and management decisions would likely be similar using data from either gear. With the exception of Pawhuska Lake (which had low catch rates leading to poor precision for both species and both gears), catch rates were typically high enough to collect sufficient numbers (125 stock‐length fish) of Bluegill to adequately describe size structure with 5–20 net‐nights for fyke nets or 4–28 transects for electrofishing, but Redear Sunfish sampling would require considerably more sampling effort to produce sufficient amounts of fish in most cases (24–79 net‐nights for fyke nets or 12–57 transects for electrofishing). Spring electrofishing is the more precise (lower relative standard error) of the two sampling methods for collecting lepomids.

Use of restored floodplains by fishes of the Middle Rio Grande, New Mexico, USA

AbstractNearly 1600 ha of habitat have been restored at 300 floodplain sites of the Middle Rio Grande (MRG), New Mexico, USA, as part of a cooperative effort of the Middle Rio Grande Endangered Species Collaborative Program to conserve the endangered Rio Grande silvery minnow (RGSM). These riverside sites are designed to inundate during spring run‐off and create ephemeral habitats for other aquatic and riparian species. This study of four restored floodplain sites in May–June 2017 found that of 14 fish species captured with fyke nets, common carp (41%), red shiner (32%), RGSM (16%) and white sucker (9%) dominated total numbers. Adult RGSM included 42% gravid females, 36% ripe males and 22% spent females, suggesting that this endangered species was spawning in and near these floodplains. Larval sampling also showed that restored sites and adjacent mainstem banklines were being used as nursery habitats, where RGSM larvae dominated six and nine species with 80% and 74% of total numbers, respectively. System‐wide proportions of RGSM larvae by phase suggest that larvae leave the floodplains and move to mainstem banklines beginning as late mesolarvae and metalarvae (14–22 days post‐hatch), and most depart by the juvenile stage. Altogether, 15 fish species were encountered in restored floodplain sites in 2017, compared to 16 species reported in concurrent annual mainstem monitoring. This study and others show that most fish species of the MRG move onto restored and natural floodplains equally in spring, and many use these habitats for spawning and as larval nurseries.

Biological parameters and current status of European eel (Anguilla anguillaLinnaeus, 1758) from Asi River, Northeastern Mediterranean region, Turkey

The biological characteristics of eels from the Asi River, Turkey, were assessed between December 2017 and November 2018. Eels were sampled monthly using fyke nets (operated by professional fishermen), yielding a total of 509 specimens. Total length and weight were measured, sex, age and maturity stages (silver or yellow eel) were determined. Catch Per Unit Effort (CPUE) was calculated for both biomass per unit effort and numbers caught on a monthly and annual basis. The length-weight relationships (LWRs) of silver and yellow eel was W = 0.009*TL3.22 (n = 262) and W = 0.0106*L3.09 (n = 247), respectively. The age of the sampled fish ranged from year class II to VI. Von Bertalanffy growth parameters were estimated as L∞=69.25 cm, K = 0.43 1/year, t0= −0.41 and phi prime index (ǿ)= 3.31 for all samples. The overall eel fishing mortality rate (F) was 0.31 year-1, and the exploitation and survival rates of silver stage eels were estimated with 30% and 39%, respectively.

Factors Influencing Abundances and Population Size Structure of the Threatened and Endemic Cyprinodont Aphanius iberus in Mediterranean Brackish Ponds

Aphanius iberus is an endemic cyprinodontoid fish species of Mediterranean ponds in danger of extinction. In this study, we studied some abiotic and biotic factors that can influence A. iberus’s size structure and density in Mediterranean brackish ponds. We sampled fish using fyke nets in 10 ponds of Empordà (Spain) during the spring season. Our results showed that a better ecological status (according to the Water Quality of Lentic and Shallow Ecosystems (QAELS) index), pond’s depth and pond’s isolation (reflected by an increase in total nitrogen) were related to larger individual sizes and more size-diverse populations. Increasing the salinity is known to help the euryhaline A. iberus acting as a refuge from competitors. Nevertheless, our results showed that higher conductivities had a negative effect on A. iberus’s size structure, leading to a decrease in the mean and maximum size of the fish. Fish abundance (expressed as captures per unit of effort (CPUE)) seemed to increase with increasing the pond’s depth and total nitrogen (the latter reflecting pond isolation). In conclusion, our results suggest that achieving a better pond ecological status may be important for the conservation of endangered A. iberus, because better size-structured populations (i.e., larger mean and average lengths) were found at higher water quality conditions.

Comparison of traditional and environmental DNA survey methods for detecting rare and abundant freshwater fish

Abstract Detecting rare species is often a necessity for conservation and management, yet challenging for many field survey methods. Environmental DNA (eDNA) is a highly promising solution that has been shown to outperform many established survey methods. Macquarie perch (Macquaria australasica) is an endangered native species that has declined significantly in range and abundance. Detection of M. australasica was compared with an abundant alien fish species (Oncorhynchus mykiss) using eDNA and three conventional survey methods: gill nets, electrofishing and fyke nets. eDNA occupancy estimates for both fish species were compared using four different models to investigate what effect these differences have on false positives and false negatives for the rare and common fish species. These models used unadjusted eDNA detections in water samples, eDNA detections that have been screened using a limit of detection method to remove potential false positives, eDNA data supplemented with a second survey method, or eDNA data augmented with sequencing of positive polymerase chain reaction replicates. eDNA surveying as a single detection method was found to be more efficient and sensitive compared with each capture method separately and combined. Occupancy estimates for the common and rare species did not vary significantly between the four site occupancy‐detection models, suggesting that supplementary data may not have as much effect on occupancy estimates compared with other approaches such as temporal or spatial sampling. We conclude that eDNA outperforms the three established survey methods for both a rare and common freshwater fish species. Although there was no significant effect of augmenting eDNA survey methods with other survey data, additional data may improve confidence in detection, and provide confirmatory evidence for unexpected or new detections of a species.

Integrating freshwater wetland science into planning for Great Barrier Reef sustainability

Abstract The paper ‘Biodiversity values of remnant freshwater floodplain lagoons in agricultural catchments: evidence for fish of the Wet Tropics bioregion, northern Australia’, published in Aquatic Conservation: Marine and Freshwater Ecosystems in 2015, has contributed in several ways to the integration of freshwater wetland science within new catchment management policies and practices for Great Barrier Reef (GBR) sustainability. The Tully–Murray biodiversity study developed novel protocols to sample larval, juvenile, and adult fish life‐history stages in floodplain lagoons using a combination of boat‐based backpack electrofishing and fyke netting. In addition, hydrological and hydrodynamic models were applied in a completely new way to quantify the timing, extent, and duration of water connectivity across floodplain streams, cane drains, and wetlands. Combining the two novel approaches enabled an analysis of lagoon fish assemblage patterns in relation to environmental gradients, especially floodplain hydrology, connectivity patterns, and measures related to agricultural land use. In demonstrating the importance of different levels of connectivity for different biodiversity outcomes in freshwater floodplain lagoons of the Tully–Murray catchment, the subject paper established that floodplain connectivity needs to be taken into consideration in wetland management practices. The timing of the subject publication was fortuitous. It coincided with the preparation of the evidence‐based 2017 Scientific Consensus Statement on land‐based water quality impacts on the GBR. As one of the few freshwater wetland ecology publications for the catchments of the GBR at that time, this paper played an important role in demonstrating freshwater wetland values, fish conservation options, and management imperatives to sustain wetland ecological health and services in GBR catchments. By advancing the understanding of factors driving biodiversity patterns, and the importance of connectivity and ecohydrological processes in freshwater floodplain wetlands of the GBR catchment, the Tully–Murray study helped to drive new policy directives for the protection and restoration of catchment, floodplain, and estuary functions, and connectivity, now embedded in the Reef 2050 Long‐Term Sustainability Plan 2018, an overarching strategy for managing the GBR over the next 35 years, and complementary Queensland environmental legislation.

Development of integrated seaweed culture and capture fisheries in Indonesia

Seaweed development has had positive impacts on surrounding environments and fisheries resources, even using traditional technologies. The integration of aquaculture and capture fisheries will have a multiplier effect on fish farmer income as well as supporting the development of the aquaculture sector. This research aimed to optimize the utilization of fisheries resources around seaweed culture areas. Two case studies were conducted at Libukang Island, Jeneponto District, South Sulawesi, and at Sarudu village, North Mamuju District, West Sulawesi. Resource use in seaweed culture areas was optimized through the design, construction, and implementation of improved fishing gears: gill nets, bamboo traps, and fyke nets. The study results show that integrating seaweed culture and capture fisheries using these gears can increase fishermen’s incomes. The level of additional income depends on fishing intensity. In addition, seaweed culture productivity should be improved through integration with fish cage culture. The cultured fish expel waste to the environment (feed, feces, and urine) that can provide nutrients to the seaweed. The sustainability of fishing depends so much on the sustainability of seaweed culture were used as a fish aggregating device.

Length–weight relationships comparison between juveniles and adults of fish species from the mangroves of south Brazil

This study reports the length‐weight relationships (LWRs) for 8 fish species that inhabit mangroves. Many fisheries depend on mangroves, which serve as nursery and feeding areas for the juvenile stage of fishes, shrimp, and other fishery resources. In this sense, mangroves provide many ecosystem services, therefore increasing the basic biological knowledge of these ecosystems can help to understand their functioning and create conservation strategies. The majority of LWR studies do not consider juveniles, and it is important to consider these differences as juveniles can grow differently from adults. The fishes were collected from Perequê mangrove, Paraná, Brazil between 2008 and 2010. A variety of fishery gears were employed, including trammel nets, fyke nets, and traps made with plastic bottles combined with four baits. The specimens were measured (weight and length), sexed and evaluated for maturational stage. For the adults, the LWRs were calculated separately by the sex, while juvenile LWRs were estimated together. In general, there were differences in growth type between sexes and life stages. Some species showed differences compared to FishBase estimations, but this could be due to the lengths (and life stage) of the individuals used in the present study compared to FishBase. The discrepancies between adult, juvenile and FishBase estimations showed the importance of considering these aspects in studies using LWR.

A systematic review of methods used to study fish in saltmarsh flats

There is a growing body of research highlighting the importance of saltmarshes as habitats for fish for feeding, refuge from predation and reproduction. However, more work is needed on fish on vegetated marsh flats (or surfaces). We reviewed 60 studies that used 21 methods to sample fish assemblages on saltmarsh flats. Drop samplers, fyke nets and pop nets were most frequently employed, with considerably more studies being conducted in graminoid than succulent marsh. Reporting of sampling temporal and tidal details, environmental variables and fish attributes was inconsistent. Most of the papers focussed on one or more of conservation management, comparisons among habitat types, and the use of saltmarsh (including fish activity type or residency status). Important potential areas of research include the relationships between the fish assemblages of saltmarsh flats and coastal fisheries, the effects of invasive plant species and marsh restoration efforts in areas outside the United States, and the potential effects of sea-level rise on vegetated flats as fish habitat. Sampling methods that provide density measures are likely to be most useful for most of this research. Thus, drop samplers and pop nets are an appropriate choice, the former in graminoid saltmarshes and the latter in succulent saltmarshes.

Fukui foldable traps versus fyke nets as options for fishing European green crabs (Carcinus maenas) in soft-bottom habitats: Exploring efficiency and limiting bycatch

The European green crab (Carcinus maenas) continues to expand in Atlantic Canada and other coastal regions worldwide. Since most control measures for this species have failed, there is a need for innovative and ecologically responsible mitigation measures. One such measure is a green crab control harvesting wherein affected fishers could recoup some of their losses through value-added products. As with any new control initiative, gear choice must be carefully considered. This study assessed catch efficiency and bycatch of two common gear: Fukui foldable traps and fyke nets. Both types of gear were systematically compared in two soft-bottom areas with abundant green crab populations over the course of a field season (early May–late September). In this study, fyke nets were more efficient, catching roughly three times the number of green crabs caught by individual Fukui foldable traps. However, fyke nets also caught nearly ten times more bycatch and doubled the number of native species caught. Fyke net bycatch also included proportionally higher numbers of endangered and commercially important species, such as American eel (Anguilla rostrata) and winter flounder (Pleuronectes americanus). Although in principle Fukui foldable traps seem better suited for green crab control because of lesser bycatch impacts, further studies should find ways to increase Fukui foldable trap efficiency or test fyke nets with bycatch reduction devices.