Do intracoelomic telemetry transmitters alter the post‐release behaviour of migratory fish?

Electronic tags have become a common tool in fish research, enhancing our understanding of how fish interact with their environment and move among different habitats, for estimating mortality and recording internal physiological states. An often‐untested assumption of electronic tagging studies is that tagged fish are representative of untagged conspecifics and thus show ‘normal’ behaviour (e.g. movement rates, swimming activity, feeding). Here, we use a unique data set for potamadromous walleye (Sander vitreus) in Lake Huron and Lake Erie tributaries to assess whether the lack of appropriate controls in electronic tagging could seriously affect behavioural data. We used fish tagged in previous years and compared their migratory behaviour during the spawning season to fish tagged in a current year at the same location. The objective of the study was to determine whether intracoelomic acoustic tag implantation altered downstream movement of walleye after spawning. Fish tagged in a given season travelled slower downstream from two river spawning sites than fish tagged in previous years. Fish tagged one or two years earlier showed no differences between each other in downstream travel time, in contrast to fish tagged in a given year. Our results support notions that standard collection and intracoelomic tagging procedures can alter short‐term behaviour (i.e. days, weeks, months), and as such, researchers should use caution when interpreting data collected over such time periods. Further, whenever possible, researchers should also explicitly evaluate post‐tagging effects on behaviour as part of their experimental objectives.     

Movements of pike, Esox lucius, in Lower Lough Erne, determined by mark–recapture between 1994 and 2000

Abstract Between 1994 and 1997, 508 pike, Esox lucius L., were tagged in Lower Lough Erne (LLE), Northern Ireland. By August 2000, 79 of these fish were recaptured. Ten of 27 pike recaptured and released a second time were then captured a third time. Distance from tagging to recapture site ranged from 0 to 16 km, with most recaptures within 10 km. Pike dispersed widely after spawning, an observation supported by netting survey data, and tended to return to the same spawning sites year after year. The usefulness of designated sanctuary areas free of commercial fishing, intended to maintain a stock of pike reserved for angling was evaluated. To protect angling stocks of pike from commercial fishing, sanctuary areas should be somewhat larger than at present.     

Diplodus spp. assemblages on artificial reefs: importance for near shore fisheries

Abstract  Artificial reefs have been deployed along the southern coast of Portugal (Algarve) since 1990 to enhance artisanal fisheries. The objectives of this study were to: (1) describe the colonisation process; (2) assess the role of the artificial reefs in terms of juvenile recruitment and growth and as mating/spawning areas and (3) evaluate the potential of artificial reefs as near shore artisanal fishing grounds for three economically important fish species, Diplodus bellottii (Steindachner), Diplodus sargus (L.) and Diplodus vulgaris (Geoffroy Saint-Hilaire). The fish assemblages were monitored after the deployment of a large artificial reef (Faro/Ancão) in 2002. Colonisation rates for the three species were fast. Artificial reefs play a multiple role for Diplodus spp., acting as recruitment, growth and nursery areas for juveniles, and spawning/mating areas for adults, and can thus be considered essential fish habitat. Three months after deployment of the artificial reefs, exploitable biomass was 16, 29 and 8 kg per reef group, respectively, for D. bellotti , D. sargus and D. vulgaris . These results indicate that artificial reefs quickly become good fishing grounds, where suitable financial yields may be obtained by fisher. Moreover, the artificial reefs became new and alternative fishing grounds, allowing reduction of fishing effort over traditional rocky areas that are scarce along the Algarve coast. Management measures for artificial reefs, in terms of fishing strategies, are discussed.     

Simultaneous estimation of instantaneous mortality coefficients and rate of effective survivors to number of released fish using multiple sets of tagging experiments

ABSTRACT:   A method is proposed for estimating two instantaneous mortality coefficients, and rate of effective survivors to number of tagged fish released, using exact times at liberty from multiple sets of tagging experiments. Effective survivors are defined here by the product of survivors immediately after releasing and reporting rate of recaptures. A least-squares method was applied to estimate the parameters using statistical models expressing the numbers of effective survivors, which were calculated by a principle similar to virtual population analysis. In order to investigate the statistical performance of the method, simulation trials using operating models were carried out. The method was applied to data of tagging experiments for alfonsino Beryx splendens from 1957 to 1969, off Kanagawa Prefecture. In most of the results of simulation trials, the method yielded estimates of natural mortality coefficient of which expected values were within ± 12% of true values. Estimates of natural mortality coefficient, fishing coefficient and the rate of effective survivors for alfonsino are 0.57 (per year, 95% confidence limits [CL] 0.40–0.69), 0.094 (per year, 0.03–0.25) and 0.39 (0.12–1.00), respectively. Modifications for the generalization of the method and notes on its applications are discussed.     

Evaluation of visible implant elastomer tags for tagging juvenile gilthead seabream (Sparus auratus L.); effects on growth, mortality, handling time and tag loss

The use of the fluorescent visible implant elastomer (VIE) tagging system in juvenile gilthead seabream, Sparus auratus L., between 7 and 18 g was examined. Four different colours (red, green, orange and yellow), three body positions (dorsal, lateral and caudal) and two orientations (horizontal and vertical) were tested. The mean tag application time for each fish was 15.7±0.32 s. There was no mortality associated with the method of tagging. The most visible tag colour was red. Injection orientation had a significant effect on length, width, fragmentation and fluorescent intensity of the tag. Horizontal tagging is recommended because of high fluorescent intensity, low fragmentation and for double tagging. There were no differences in growth between untagged controls and the VIE‐tagged fish.     

Movement, social cohesion and site fidelity in adult koi carp, Cyprinus carpio

Abstract  Koi carp is an ornamental variant of the common carp, Cyprinus carpio L., that was introduced to New Zealand in the 1960s and has since become a major aquatic pest. A total of 1265 wild adult koi carp were caught by boat electric fishing, dart tagged and released at multiple sites in the lower Waikato River and associated lakes and wetlands between September 2002 and February 2005. Subsequent recaptures by boat electric fishing and recreational fishing returned 76 koi carp (6% of all tagged fish). Of these, 85% were recaptured less than 5 km from their release site; only one fish moved more than 50 km. On seven occasions, pairs or small groups of koi carp (20% of all tag returns) that had previously been tagged and released at the same locations and times were subsequently recaptured together after considerable periods of time at liberty (mean 551 days ± 419 SD). Adult koi carp in the Waikato River showed a high degree of site fidelity, exhibited prolonged social groupings and females moved downstream more often than males.     

Movement of flathead catfish in the Missouri River: examining opportunities for managing river segments for different fishery goals

The dispersal patterns of 2939 flathead catfish, Pylodictis olivaris (Rafinesque), were determined within a 90‐km section of the Missouri River, USA. Fish were captured by electric fishing and tagged in early June each year from 1999 through 2001. Dispersal was determined via angler tag returns between 1999 and 2001 or by subsequent recapture during sampling 1 or 2 years after initial tagging (June 2000 or 2001). Dispersal was localised for the majority of the 370 flathead catfish recaptured in the Missouri River. Over 80% of recaptures were within 5 km of tagging location, and 94% were within 20 km of tagging location. Maximum displacement was 160 km. To examine differences in movement patterns of various sized fish, flathead catfish were placed into one to three size groups (305–380, 381–507, or ≥508 mm). A significant difference (P < 0.001) was detected in dispersal patterns among the three size groups; the largest size group moved greater distances than either of the smaller size groups. Movements average 4.5, 5.6 and 12.6 km for small, medium, and large size classes, respectively. Dispersal movements of flathead catfish in the Missouri River appeared to be localised, suggesting that different sections of the Missouri River could be managed for different fishery goals for flathead catfish to accommodate a variety of angler types and desires.     

Application of bioelectrical impedance analysis as a method for estimating composition and metabolic condition of southern bluefin tuna (Thunnus maccoyii) during conventional tagging

Tagging fish without gathering physiological information may be a wasted opportunity. We tested bioelectrical impedance analysis (BIA) for measurement of relative condition of southern bluefin tuna (Thunnus maccoyii) during conventional tagging at sea. We refined the equipment and method by measurement of 360 fish during conventional and acoustic tagging. Our results demonstrate that BIA is an accurate measure of condition for southern bluefin tuna in the same way it has been shown to be for metabolic condition and composition in other vertebrates including humans. Further, there is sufficient variation in BIA measures of the natural population to give meaningful measures of both metabolic condition and composition between groups at different times and developmental stages. Condition of tuna in this study may be related to the ocean environment just prior to measurement. BIA meets the necessary objectives for measuring fish condition during tagging as it is shown to be harmless, reliable, quick, and effective and does not disrupt conventional tagging operations. In the light of these results this type of condition measurement should be taken wherever possible in future tagging operations for this and other similar species, which will generate new insight into the ecological challenges faced by pelagic fishes. The ability to relate recent ocean environments and subsequent patterns in fish survival may lead to changes in the way tagging data is interpreted.     

Conservation of spawning time between years in lumpfish Cyclopterus lumpus and potential impacts from the temporal distribution of fishing effort

Lumpfish, Cyclopterus lumpus L., has an extended ovary development period and a relatively long spawning season. It therefore seems unlikely that individuals spawning later in the season would be able to recover from spawning and develop their gonads in time to spawn during the early part of the season the following year. The hypothesis that individuals spawning early or late in a spawning season would spawn early or late the following year was tested using fish tagged in Iceland between 2008 and 2017. The tagging date and recapture date the following year were positively correlated with an average of 356 days at large (DAL). Fish sampled from the fishery indicate that tagging/recapture date gives an indication of spawning time. From this, it was concluded that spawning time in the current year can be used to predict spawning time the following year. As fishing effort was greatest at the end of April/beginning of May, it seems likely that fish that come to spawn at this time will be subject to a higher fishing mortality. Therefore, they will be less likely to spawn successfully than fish spawning earlier or later in the year. If spawning time is under genetic control, then this could have consequences for the spawning phenology of lumpfish.     

Tracking bluefin tuna reproductive migration into the Mediterranean Sea with electronic pop‐up satellite archival tags using two tagging procedures

Thirteen adult bluefin tuna were tracked with electronic pop‐up satellite tags during their reproductive migration towards Mediterranean spawning grounds as they entered the Strait of Gibraltar. Fish were caught in tuna traps and tagged either underwater, with the aid of a modified spear gun, or on the deck of the boat. Fish tagged on board initially showed a shallower behavior than those tagged in the water. The pattern of horizontal movements was also different between both groups. Shortly after tagging, the eight fish tagged in the water entered the Mediterranean Sea. Six of these fish reached the spawning ground located southwest of the Balearic archipelago before heading back for the Atlantic, whereas the other two traveled farther east, reaching its easternmost longitudes between Formentera and Sardinia and the South Tyrrhenian Sea, respectively. In contrast, two out of the five fish tagged on board never entered the Mediterranean Sea, and another one did enter the Mediterranean when the reproductive season was already over. These results suggest an impact of the tagging procedure on the post‐release behavior of bluefin tuna. Excluding the tags that popped‐off east of the Strait of Gibraltar, bluefin tuna stayed in the Mediterranean Sea for 22–28 days. Analysis of the median depth indicated a shallow behavior during both day and nighttime throughout the return phase of the fish from the Mediterranean Sea to the Atlantic Ocean with the exception of the area around the Strait of Gibraltar, where they showed a deeper behavior that coincided with a marked vertical gradient in the currents.     

Tagging: on the use of passive integrated transponder (PIT) tags for the identification of fish

To determine the efficacy of passive integrated transponder (PIT) tags for marking rohu Labeo rohita (Ham.) in the selective breeding programme, a series of experiments has been carried out at the Central Institute of Freshwater Aquaculture (CIFA) under the Indo–Norwegian project of ‘Selective breeding of rohu’. Six groups of rohu fingerlings with weight ranging from 2 g to 20 g were tagged with PIT tags to determine a suitable size range for tagging. Fingerlings weighing 8–15 g were found to be quite suitable for tagging with a PIT tag. Recovery of the PIT tag depends upon the survival of tagged fish under field conditions. Rejection of the PIT tag by rohu was observed to be only 0.05%. Through effective management practice, the survival of tagged fish increased up to 95%, and thus tag loss was minimized.     

Gear restrictions create conservation and fisheries trade-offs for management

Gear-based management for coral reef fisheries is often overlooked in the scientific literature. Empirical studies have demonstrated the conservation benefits of gear-restricted areas (i.e. prohibiting fishing gears), which can support greater biomass than unrestricted areas and protect species that play key functional roles. However, population dynamics of functional feeding groups of reef fishes under specific gear-restriction regimes remains uncertain. Here, we constructed a multi-species, length-based fisheries model to observe relative biomass and catch of reef fishes under various gear-restriction management scenarios. We used fishery-dependent and fishery-independent data to determine the catchability of functional groups and selectivity of size classes for hook-and-line, net and spear fishing, which are widely used gear types on coral reefs globally. Our model revealed trade-offs involved with gear-restriction management such that no single management strategy was able to maximize biomass or catch of all functional groups simultaneously. Also, we found that spear fishing (i.e. prohibiting hook-and-line and net fishing) maintained the highest total biomass summed across functional groups, whilst hook-and-line fishing (i.e. prohibiting net and spear fishing) and a ban on spears maintained the lowest biomass. However, hook-and-line fishing generated the highest catch-per-unit-effort. Our model results were primarily driven by differential growth rates, maximum per capita production of recruits, and catchability of functional groups targeted by each fishing gear. We demonstrate that gear restrictions can be a critical management tool for maintaining biomass and catch of certain functional groups but will likely require additional management to protect all key functional feeding groups of coral reef fishes.     

Evaluation of visible implant elastomer tags for pathogenesis research in Nile tilapia (Oreochromis niloticus)

Two different colours (red and green) of visible implant elastomer (VIE) were used in Nile tilapia (Oreochromis niloticus). The visibility, location and retention of the VIE tags was investigated and any adverse effects on fish survival and growth determined. The use of VIE tags for monitoring individual fish during a bacterial challenge with either Streptococcus agalactiae or S. iniae was also studied. The results showed that VIE treated fish were lighter but not shorter than the non‐tagged control fish and that tagging caused no mortality. The retention of tags was better at the base of pectoral fin followed by the nasal area, lower abdomen, upper abdomen and branchiostegal rays inside the operculum. During the bacterial challenge experiment individual animals could be easily identified using the VIE tags. In this preliminary study, VIE tagging appears suitable for Nile tilapia research, as with other fish species, and could be a novel method to identify individual animals during microbial pathogenesis studies.     

Fine-scale movement patterns, site fidelity, and habitat selection of ocean whitefish (Caulolatilus princeps)

The fishery for California groundfishes is managed using broad species complexes, although some non-groundfish species are managed similarly due to the perception of shared behavioral characteristics. This study integrates acoustic telemetry and a GIS to quantify movement patterns of one such species, the ocean whitefish (Caulolatilus princeps) in a marine protected area. Seventeen ocean whitefish were tagged and actively tracked over multiple 24-h periods to measure fine-scale movement patterns. Home ranges based on 95% kernel utilization distributions averaged 20,439 ± 28,492 (±S.D.) m². Fish were active during the day, foraging over sand habitat at depths averaging 21 ± 8 m, but were inactive at night, taking refuge near rocky reefs at depths averaging 15 ± 7 m. Seventeen additional fish were tagged with coded acoustic transmitters and passively tracked using automated underwater acoustic receivers for up to 1 year. Approximately 75% of these fish exhibited long-term (1 year) fidelity to home ranges in the study area. Results suggest that MPAs can be an effective means of protecting populations of ocean whitefish and based on their habitat associations, ocean whitefish can be managed separately from other reef associated groundfishes.     

Growth rate and mortality of Australian bass, Macquaria novemaculeata, in four freshwater impoundments in south-eastern Queensland, Australia

Abstract  Growth and total mortality of Australian bass, Macquaria novemaculeata Steindachner, were studied in four freshwater impoundments using data from a cooperative angler tagging programme. Growth was modelled using the computer program GROTAG. Annual growth increments varied among impoundments, ranging from 5.0 to 7.8 cm yr⁻¹ among fish 20-cm total length (TL) and 1.7 to 4.9 cm yr⁻¹ among fish 30 cm TL, but exceeded previous estimates for the species. Annual total mortality rates, based on the decrease in recapture rate with time, ranged from 0.03 to 0.07 and were lower than for other comparable species, presumably because of the prevalence of catch and release fishing in the impoundments studied.     

Migration of eels tagged in the Baltic Sea and Lake Mälaren—in the context of the stocking question

Eels (Anguilla spp.) are in decline worldwide, and the signs of reduced recruitment have been observed in continental Europe since the early 1970s. To aid recovery of the European eel, stocking is used by many European countries as a management option. In this study, tagging experiments were conducted to follow eel migration from Lake Mälaren and four sites along the Swedish east coast in the Baltic Sea. The recaptured tagged eels were retrieved from fishermen, allowing for the opportunity to investigate their origin (brackish water, stocked in freshwater or a mix in between) by otolith microchemistry and to assess for morphological differences after tagging. Several changes took place; for example, eye index increased while weight and condition decreased with migrated distance and time until recapture. In Lake Mälaren, the majority of tagged eels did not migrate out of the outlets, irrespective of their origin. Most of them were caught in the opposite direction and continued to be caught in the lake 1–3 years after tagging, with significant weight losses. Overall, overwintering is suggested to be an inferior option, but it is uncertain whether this is a natural behaviour or a result of translocation and restocking. For coastal eels, origin had no effect on migratory behaviour; a majority of the tagged eels migrated towards the outlet of the Baltic Sea. Interestingly, a minority of the recaptured eels originated from stocked fish. Instead, recaptures were dominated by natural immigrants that had spent most of their lives in brackish waters.     

Effects of tagging on migration behaviour,survival and growth of hatchery‐reared Atlantic salmon smolts

The effects of four different tagging methods (PIT, anchor T‐tag, Carlin tag and dummy radio transmitter) on survival, behaviour and growth of Atlantic salmon smolts during their downstream migration were examined in semi‐natural circular channels during a natural migration period in spring. Survival of smolts was high and tagging wounds healed well in all tagging groups. Tag loss rates were generally low, being the highest (2.5%) in the dummy radio transmitter group. Total length and body mass of the tagged and untagged smolts did not differ at the end of the experiment. Migration activity of smolts generally showed similar patterns among the treatments. However, Carlin‐tagged smolts started their migration slightly later than the PIT‐tagged fish, and smolts tagged with Carlin tag or dummy radio transmitter showed less overall migration activity than fish with PIT tag.     

辽东湾中国对虾标志放流及其增殖效果的研究

本文根据辽东湾中国对虾标志放流实验与重捕资料，对辽东湾中国对虾放流场的选择、种苗的放流规格和放流增殖效果进行了研究。根据上述实验分析表明，在辽河口海区进行对虾放流增殖是较理想的场所，在秋汛生产期洄游分布遍及辽东湾传统的中心渔场；放流种苗的适宜体长规格为5cm以上，回捕率较高，最高达3．31％。这将对辽东湾生产性对虾放流提供科学的依据。     

大亚湾黑鲷标志放流及回捕率调查

为评价大亚湾海域黑鲷(Acanthopagrusschlegelii)增殖放流效果,使用塑料椭圆标志牌(plasticovaltags,POTs),开展了黑鲷幼鱼标志保持率与生长实验。结果显示,背鳍鳍棘基部第4～6鳍棘下方5mm左右的背部肌肉为最适标志位置, 90 d后标志保持率为81.76%。POTs标志黑鲷幼鱼45 d内生长与对照组无显著性差异(P>0.05),而90 d后标志组生长显著缓于对照组(P<0.05)。并于2014—2016年每年1次在大亚湾开展黑鲷幼鱼标志放流试验。采用有奖回收方式进行标志鱼回捕,测量体长、体重,收集回捕日期、回捕地点、回捕方式等信息,整理分析相关数据。3年共放流标志黑鲷幼鱼60115尾,共2758尾回捕标志鱼被定置网、流刺网及垂钓捕获(总回捕率4.59%);大规格放流苗种回捕率高于小规格放流苗种;垂钓回捕鱼数量占总回捕数量的比例为62.08%。通过对反馈信息的分析,认为放流后的标志鱼最初主要沿湾内和湾外两个方向呈近岸辐射状扩散,最远扩散距离约70 km。放流后1～2个月标志黑鲷生长较慢,随后相对加快,放流5～7个月后,黑鲷幼鱼体长、体重分别增长59.51%～127.20%和322.75%～989.83%。结论认为,POT是黑鲷幼鱼体外标志的适宜选择;在研究海域,放流后的标志黑鲷更易于被垂钓方式捕获;丰富的食物和可供躲避敌害的空间是影响其扩散、生长的因素。     

High variability in spawning migration of sea trout,Salmo trutta,in two northern Swedish rivers

Abstract Telemetry was used to examine spawning migration of sea trout, Salmo trutta L. (n = 126), in two rivers in northern Sweden. The spawning areas defined by radio‐tagged fish differed between the river systems. In the River Vindelälven, sea trout spawned in the main stem and 80% of tagged individuals returned to areas where hatchery‐reared juveniles had been previously stocked. In the River Piteälven, 74% of tagged sea trout ascended tributaries for spawning. Tagged fish were categorised into three groups of migratory pattern. cart (classification and regression tree) analysis indicated that distance from tagging location to spawning site (S_dist) explained the migratory patterns. Large S_dist separated fish with stepwise upstream migration from those with up‐ and downstream migrations and one‐directional direct migration. Fish tagged early in the season migrated the longest distance to spawning areas. Stocking locations and sex explained the large search behaviour up‐ and downstream in the rivers. The findings are important for the sustainable management of sea trout in the Gulf of Bothnia.