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1.
A total of 2676 trevally, Caranx georgianus Cuvier, was tagged in the Hauraki Gulf and Bay of Plenty during 1973 and 1974. Fish were caught by research trawler, anaesthetised, and tagged with spaghetti tags. During the following 5 years, 130 tags (4.9%) were returned. Most recaptures came from set nets (42%), followed by commercial trawlers (22%), Danish seiners (11%), research trawl (9%), other methods (7%), and method unknown (9%). Excluding tagged fish taken by research trawl, 85% of tag returns were made by commercial fishermen and 15% by amateurs. Initial tagging mortality was low, but was probably significant over an extended period. Movements of trevally were limited; 88% moved less than 30 nautical miles (55 km) from the release site. However, there was sufficient movement to regard trevally from the Bay of Plenty and probably also the Hauraki Gulf as one stock.  相似文献   

2.
During 1974, 5045 snapper Chrysophrys auratus (Forster) were tagged at various locations along the north‐east coast of the North Island. Most were trawl‐caught using a canvas cod‐end in shallow inshore areas. Four types of tags were used, of which two were found to be effective: a large single‐barbed dart tag, and a lock‐on spaghetti tag. For the period up to the end of October 1975, 88 (1.74%) were returned. Highest returns were from the Hauraki Gulf (2.3%) and lowest from Northland (nil). Analysis of the recapture data showed that most movements were local, with a mean distance between tagging site and recapture position of 13.9 nautical miles (25.7 km). Four movements greater than 50 miles (92.6 km) were recorded. Local movements in the Hauraki Gulf were associated with the spring/summer spawning period. This movement, out from inshore areas which are closed to seiners and trawlers, and schooling behaviour, are thought to be the main factors contributing to the peak in snapper catches at this time of the year.  相似文献   

3.
Increases in the density of exploited species on unfished reefs logically implies that some individuals are at least temporarily resident, or show fidelity to a particular area. We tagged snapper (Pagrus auratus (Bloch & Schneider 1801)) in the Leigh Marine Reserve, New Zealand using visible implant fluorescent elastomer tags, recoverable by diver visual sightings without the need to recapture the fish. Batch tagging of snapper (n = 907) was done during an angling survey in June and December 1996, and individually coded tags were implanted by divers (n = 117) in January 1999. Snapper tagged during both programmes were recovered on irregular intervals from 1997 to 2000. There were 71 recoveries of batch tags within 500 m of their tagging sites, and these recoveries were still being made >3 years after tagging: Of individually coded fish, 49 (42%) were seen, sometimes repeatedly over several months, close to their respective tagging sites. These observations included snapper as small as 23 cm fork length, contradicting the commonly held impression that only large snapper take up long‐term residency on reefs. This preliminary evidence suggests that some snapper exhibit site fidelity to areas only a few hundred metres wide, and in the absence of fishing may occupy the same area for years.  相似文献   

4.
In late 1987, bluenose (Hyperoglyphe antarctica) were tagged with streamers attached to fish hooks, at six commercial fishing grounds between Gisborne and Cape Palliser, New Zealand. The tagged hooks were fished on commercial trot lines, but were attached with traces of 5.5 kg breaking strain nylon that broke when the fish took the hook and struggled to escape. Based on catches from full strength control lines fished simultaneously with the detachable gear, 1971 bluenose were tagged. In the subsequent 8.5 years, 44 tagged bluenose (where both the sites of tagging and recapture where known) were recaptured. All but seven of these returns occurred in the first year after tagging, indicating that the rate of long‐term tag retention was not good. Bluenose appeared to be relatively sedentary in the short term, but were capable of quite rapid and extensive movement. Four tagged fish had travelled distances in excess of 450 km, with movements to both the north and south of the tagging area. These data indicate that bluenose off the eastern coast of New Zealand between North Cape and Kaikoura probably comprise a single biological stock.  相似文献   

5.
The results of three snapper tagging cruises in the Hauraki Gulf area to estimate population size and annual exploition rate are presented. Eight hundred and thirty‐two snapper were tagged around Great Barrier Island in August 1975; in the inner Hauraki Gulf 1743 were tagged in June 1976 and 2685 in October 1976. Estimates of tag loss due to the combined effect of shedding of tags and tagging mortality were made, and the crude tag return rates were adjusted accordingly. The combined returns from commercial and amateur fishermen for the first year after tagging, adjusted for tag loss, were: Great Barrier Island, 19 (2.3%); inner Hauraki Gulf, June tagging, 98 (5.7%), October tagging, 179 (6.8%). Tag return rates from different parts of the study area varied considerably.

Calculations of the population size for the inner Hauraki Gulf (fishery statistical areas 006 and 007) were made from tag returns of longline and set net fishermen and their catch statistics taken from the monthly fishing returns; Petersen's method gave population sizes of 43 million (returns from June tagging) and 36 million (October). The catch statistics are thought to considerably under‐record the real landings, and better estimates of the population size may be 71 million and 60 million respectively.  相似文献   

6.
Tag recovery rate is an important parameter for estimating exploitation and natural mortality in fished populations. Passive integrated transponder (PIT) technology can record 100% of PIT tagged animals passing within the detection limit of a PIT tag scanner. However PIT tags and PIT tag scanners are expensive compared with conventional visual tags and PIT tags are not detectable without scanners. We used simulation to evaluate the hybrid PIT tag which has the PIT tag incorporated into a conventional tag allowing both electronic detection capability by a scanner and visual detection by fishers. Simulated estimates of the precision and accuracy of exploitation and natural death rates for two lobster fishery management regimes: a 7‐month season for both sexes and a fishery with a 10‐ and 6‐month season for males and females, respectively, were used to determine the benefit of PIT tags. For a project budget of AU#DL200,000, hybrid PIT tags and 10% of the fleet being equipped with scanners produced more precise and accurate estimates of exploitation rate and natural death rate until tag reporting rate by fishers exceeds 40% for the two‐gender management regime and 90% for the 7‐month combined sex regime. Increasing the number of scanners to 20% of the fleet resulted in fewer hybrid PIT tags being inserted for the same cost and did not improve the precision or accuracy of estimates. Increasing the number of lobsters tagged by tagging during a higher catch rate period improved the precision of exploitation and natural death rate estimates at lower tag reporting rates for the conventional tag scenario, but did not alter the tag reporting rate required to make conventional tagging more beneficial than hybrid PIT tagging. Increased tag reporting rate by the 90% of the fleet that were not equipped with scanners had no significant impact on the precision or accuracy of estimates for either management regime.  相似文献   

7.
Tagging effects and loss rates of 60 Roman Chrysoblephus laticeps tagged with dart tags with barbs (D-tags), T-bar filaments (T-tags) and visible implant fluorescent elastomer (VIFE) tags were investigated. The fish were tagged and monitored in a controlled tank experiment over a period of 198 days. Application technique and underwater visibility of VIFE tags were assessed in a preliminary experiment on Roman and on fransmadam Boobsoidia inornata. The use of 25-gauge needles improved VIFE tag application. Whereas VIFE tagging caused fin rot in fransmadam, it had no negative effect on Roman. VIFE tag codes could be identified underwater from a distance of 3m under ambient light. There was no significant difference in growth rates among groups of Roman with different tags and controls, but rates of tag loss were high for D-tags (53%) and T-tags (73%). Although some of the VIFE marks were incomplete, all VIFE-tagged fish were individually recognised at the end of the study. The results highlight the need to take cognisance of the high tag loss rate of conventional tags during the design of mark and recapture studies.  相似文献   

8.
Seabed mapping, spatially referenced trapping, and mark‐recapture methods have all been useful tools in ecological studies of lobsters and other benthic animals. Here we integrate the three methods to evaluate local population dynamics and movements of American lobsters, Homarus americanus, in coastal fishing grounds in Maine, United States. The study was conducted on five study areas of different size, and used two different sampling protocols. At one site (1 km2 in area) we used a monthly mark‐recapture sampling interval over a 6‐month period, only tagging a subsample of the catch. At four smaller sites (0.3 km2) we used a shorter‐term approach, sampling at 3–4‐day intervals for a 2‐week duration, tagging the entire catch. Tagging data were analysed with a modified Jolly‐Seber model adapted for continuous sampling to estimate population abundance, gains (immigration), and losses (emigration and mortality). Side‐scan sonar surveys of the seabed combined with diver‐based population surveys, stratified by substrate type, provided an independent comparison to mark‐recapture‐based estimates of abundance over the same areas. Spatial referencing of trap catch also allowed us to relate catch rates and lobster movements directly to seabed features. The longer‐term tagging data on the larger study area provided abundance estimates that were more consistent with the diver observations, and estimates of gains and losses statistically more robust, than those derived from the shorter‐term effort on the smaller sites. The flux of lobsters followed the well known seasonal movements on these fishing grounds, with gains and losses from the larger study area ranging over 1000 individuals per day, and an estimated mid‐summer peak density of >65 000 lobsters per km2 (individuals >50 mm carapace length). This approach may lend itself to broader application with the American lobster.  相似文献   

9.
Individual specimens of Myripristis jacobus Cuvier, 1829 and Scarus taeniopterus Lesson, 1829 were collected from Gopalpur‐on‐sea, Odisha coast, Bay of Bengal. Both the fish samples were assigned species level tags using the conventional taxonomic methods. The capture of both the fish species is of particular interest in that they were new to the Bay of Bengal. Molecular analysis using the mitochondrial cytochrome oxidase subunit I (COI) gene showed high confidence sequence similarity in species identification. The resultant phylogenetic relationships strongly support the monophyly of both the genus with congruent clustering of both the species according to their morphological identification. In addition, the time tree produced is in complete agreement with the recent studies. These studies conclusively prove that both the species might have been originated during the middle to the late Miocene period. Furthermore, both fish species are typical inhabitants of stigmatized coral reefs, confined to the reef regions. These fish species perhaps migrated to the Bengal Bay from the Andaman and Nicobar Islands reef regions because of climatic changes.  相似文献   

10.
This study made use of data from three long-term fish tagging projects along the South African coastline to investigate the movement behaviour of the endemic black musselcracker Cymatoceps nasutus (Sparidae). From 1984 to 2016, a total of 3 430 C. nasutus (178–980 mm fork length) were tagged (with small plastic dart tags) throughout the species’ distributional range, with an overall reported recapture rate of 7.2%. Recaptured individuals displayed high levels of residency, moving an average of 14.8 km, with time-at-liberty ranging from 0 to 6 809 days. The majority of recaptures (84.6%) were made within 1 km of the tagging sites; however, some large-scale movements, of up to 528 km, were recorded. Although C. nasutus individuals moving greater distances were characterised by greater mean sizes (mm fork length) at time of recapture, the distances moved by juveniles were not significantly different from those of adults (p > 0.05). Low levels of connectivity among coastal regions were therefore expected due to the high degree of residency displayed by this species. Combining traditional management approaches together with a well-designed network of no-take marine protected areas is likely to be the most effective way to protect this vulnerable species. A lack of data on the movements of adults remains a challenge, but this could be overcome by tracking large individuals tagged with long-life acoustic transmitters.  相似文献   

11.
On March 19, 1984, more than 170000 gallons of oil were spilled into the Columbia River. We had recently developed analytical methods for estimating the exposure of fish to aromatic compounds by measuring the concentrations of metabolites of these contaminants in fish bile. The oil spill provided an opportunity to field test our methods in assessing the exposure of fish to petroleum aromatic compounds from the spilled oil. Our findings indicated that, within 5 days after the spill, mean concentrations of metabolites of aromatic compounds in the bile of white sturgeon (Acipenser transmontanus) captured 57 miles downstream from the spill were significantly higher than those of sturgeon caught upriver.  相似文献   

12.
Tag reporting rate is an important parameter required for estimating fishing and natural mortality in fished populations. It is an extremely difficult parameter to estimate and can vary both during the fishing season and between fishing years. Improving tag reporting rates has been identified as a cost‐effective way of improving precision in fishing and natural mortality estimates derived from tagging data. In this study we evaluated the use of passive integrated transponder (PIT) tags to improve tag reporting rates in a lobster (Jasus edwardsii) trap fishery. To minimise the risk of PIT tag ingestion by consumers, we tested insertion of the PIT tag into the base of the antennae, the base of the walking leg, and the base of the telson. The base of the antennae proved to be the best option for lobster health although impacts were observed at all tag insertion sites. We further developed and tested a hybrid tag that combined a conventional external T‐bar tag with a PIT tag embedded within the shaft. PIT tag scanners were positioned in bottlenecks in the capture process so that all lobsters retained on board the vessel were passed through a scanner. Thus, the tag reporting rate was expected to be 100% for the subsample of the fleet fitted with scanners when scanners were operational. Scanner malfunction was a major issue and further engineering solutions are required to ensure that scanners are reliable when working in harsh marine conditions such as on‐board fishing vessels. Advantages of the hybrid tag are: the ability to be detected by both automatic detectors and fishers; known tag‐induced mortality and tag loss rates from previous research; and PIT tagging without risk of human ingestion.  相似文献   

13.
A new conservation measure aimed at protecting the larger broodstock (females with a carapace length between 115 and 129 mm, i.e., window‐size females, WSF) to enhance egg production was implemented in 2003 for the American lobster (Homarus americanus) fishery in the southern Gulf of St. Lawrence, Canada. To assess the effectiveness of this new measure, a tagging project was carried out between 2004 and 2007 in the Hillsborough Bay area with the collaboration of local harvesters. Based on a single mark‐recapture Petersen model, the estimated catch rates of WSF not carrying eggs under the abdomen in the study area varied between 40% and 53%. The catch‐per‐unit‐effort (animals per 100 traps) of both berried (egg‐bearing) and non‐berried WSF increased from 0.2 to 0.8 and 1.0 to 1.6, respectively, between 2004 and 2007. Based on the estimated number of non‐berried WSF in the population observed during the spring fishery between 2004 and 2007, the potential total egg production for WSF was estimated at 1.1 billion in the study area. From this total, 515 million eggs would have been produced by WSF directly protected by the conservation measure, i.e., females that would have been harvested if not for the new regulation. Finally, the contribution of berried WSF to the annual egg production in the study area increased from 4% to 23% between 2003 and 2007 based on the at‐sea sampling programme and the fecundity curve. WSF that represented 10% of the total berried female population in 2007 contributed 23% of the annual egg production. Hence, the protection of WSF seems to be an effective conservation measure to increase egg production based on the catch‐per‐unit‐effort and egg production.  相似文献   

14.
Understanding movement behaviour is essential for effective management of fishery species. Dart tags were used to study coastal movement patterns of white steenbras Lithognathus lithognathus, an overexploited seabream (Sparidae) in South Africa. In total, 6 962 fish (190–1 080 mm fork length) were tagged throughout the species’ distributional range, in four long-term fish-tagging programmes. The predominant behaviour recorded was residency, with relatively short-ranging movements. More than 60% of the 351 recaptured fish were recaptured within 1 km of their tagging site, some of which were at liberty in excess of three years. Most of the juveniles (93.9%), subadults (71.7%) and adults (64.0%) were recaptured within 10 km. Occasional long-distance movements of up to 800 km were recorded. Recapture distances were positively, but weakly, correlated with fish fork length (n = 257 fish measured at recapture; r2 = 0.166, p < 0.001). Low levels of connectivity among coastal areas suggest that large-scale annual spawning migrations, as previously hypothesised for this species, are unlikely, which raises the possibility of multiple spawning sites. Seventy-seven percent of L. lithognathus tagged within three marine protected areas (MPAs) were recaptured within the same MPA, suggesting that area closures provide protection for L. lithognathus through the post-estuarine juvenile, subadult and adult life stages. We confirm that the country’s current network of coastal MPAs plays a vital role in sustaining this species, and suggest that additional closures, or otherwise substantial reductions in catch rates, are necessary for the species’ recovery.  相似文献   

15.
Understanding differences in the recapture rate between different tags (A-, B- and C-types), capture methods (rock-and-surf anglers, scientific divers and Natal Sharks Board protection nets) and life-history stages (juvenile and adult) is critical in evaluating the results obtained from cooperative tagging programmes (CTPs). A generalised linear modelling approach, using a log-linear model, was used to determine significant differences in the probability of recapture between these various factors using data from the Oceanographic Research Institute and Port Elizabeth Museum CTPs. Between 1984 and 2004, a total of 3 385 raggedtooth sharks Carcharias taurus was tagged by volunteers from both programmes along the east coast of South Africa. A likelihood ratio test indicated significant differences in the probability of recapture between A- and C-type and B- and C-type tags (p < 0.01), between different capture methods (p < 0.05) and between juvenile and adult sharks (p < 0.01). A comparison of recapture rates between members of the CTPs also indicated a marked variability in the performance of individual taggers. The study highlights important data-quality issues inherent in large CTPs.  相似文献   

16.
Two methods,tagging and ink injection,are used in the grouper releasing experiment.The studied fishes are the juvenile of Epinephelus akaara and Epinephelus awoara both artificially cultivated and caught from natural waters,and their wild adults.Experimental results show that the inhabiting behaviours for both juvenile and adult fishes show distinct regionality,which move within an area of 2n mile diameter 651 days and 48 days after being released,respectively,With the tagging method,the tagged fishes could only be recaptured in the year of release while,with the injection method,they could be caught in the lst,2nd and 3rd years,It is confirmed that in the cement tank,the tagged fishes lose their 1/3 tags.That means that the tagging method is not fit for the release research while the injection method is .Generally,the recaptured rates of injected fishes are 1.4-4.5%,3.1-13.4%and 2.7%for the lst,1nd and 3rd years,respectively.  相似文献   

17.
Scales from 17 body areas of juvenile snapper, Chrysophyrs auratus (Forster), were examined to determine scale growth characteristics, with the aim of denning the most suitable body site for routine scale‐sampling. Least‐square regressions of fish length on scale measurement from 0+ fish were calculated for several body areas, and back‐calculations were made to fish length at first annulus (L1) from a sample of 1+ fish, using both the “uncorrected” and “corrected” formulae.

The overall fish/scale relationship is curvilinear, but high correlation coefficients show that fish/scale regressions from 0+ snapper may be taken as essentially linear. Such regressions give hypothetical fish lengths at scale formation of 8–23 mm. Mid‐body scales form at 10–14 mm, caudal scales earlier, head scales later.

Back‐calculated L1 values from each area were compared with the mean for the whole body. Using the uncorrected formula there is a general trend for them to be lower than the mean at the head and higher at the tail, while the mid‐body region shows minimum variation from the mean. These variations are caused at least partly by differences in time of scale formation. The corrected formula gives smaller L1 variations and a mean back‐calculated L1almost identical to an observed L1 from independent length frequency data.

The observed variations in scale structure and growth suggest that the “pectoral area”, bounded by the lateral line and the ventral edge of the pectoral fin, is the most suitable site for scale sampling.  相似文献   

18.
From 1973 to 1976, 2430 blue cod (Parapercis colias) were tagged in the Marlborough Sounds. Tags from 84 fish (3.5%) were returned, after a mean 138 days at liberty. Of these, 71.6% had not moved significant distances. The remainder had travelled up to 41.7 km. Tag shedding rates, as indicated by multiple‐tagging experiments, were high. Results suggest that blue cod of the Marlborough Sounds and the adjacent islands belong to the same stock, and that, while some move significant distances, the majority stay in 1 place for extended periods.  相似文献   

19.
Abstract

Migrating and pre‐migrating western rock lobster Panulirus cygnus were tagged with datastorage tags that recorded temperature and pressure, which was converted to depth (Pressure (kPa) — surface pressure (kPa)/10)) at Dongara and Jurien Bay in Western Australia between December 2005 and December 2007. All lobsters were fitted with tag flotation devices, and returns were made by either commercial fishers or beachcombers who located detached tags. A total of 135 lobsters were released with “backpack” flotation tags, but only 84 (62.2%) of the backpacks carried data‐storage tags. Depths of release ranged from 5 to 113 m. Of the tagged lobsters released, commercial fishers recaptured 52 (38.5%), whereas 11 tags (8.1%) were found by beachcombers. At least 33%, and possibly up to 63%, of animals identified by their pale coloration as pre‐migrating individuals, failed to migrate. Those that did migrate (n = 11) were at liberty from 1 to 94 days and showed generally similar movement patterns in that they migrated only at night from darkness (after 2000 h) until after moonrise. However, their movement patterns were less constrained by the rising of the moon in deep water. Only 27% migrated nightly, compared with 73% that skipped migrating on one or more nights, to restart some days later. This latter proportion would likely have been considerably greater, but some migrating animals were only at large for short periods before recapture, and therefore had little time to show any variation to the nocturnal migration pattern. Individual speeds of migration during periods of activity were estimated for nine lobsters as 0.20 to 0.68 km h?1, with a mean speed of 0.44 km h?1, or 7.4 m min?1. Improved knowledge of daily movement patterns resulting from this study provides a potentially important input into technological improvements in bait and pot design.  相似文献   

20.
We used Argos‐linked Fastloc‐Global Positioning System (Argos‐linked Fastloc‐GPS) satellite tags to investigate how loggerhead sea turtles use neritic foraging habitats at multiple scales. Out of 24 turtles, six individuals used more than one foraging site, with all sites being separated by >25 km. These six individuals used up to four sites, remaining at each site for a mean of 150 days and returning to the same site a minimum of 52 days later. The other 18 turtles remained in a single site. The area within sites was not used uniformly, with 15 out of 24 turtles exhibiting complex movement patterns within and amongst up to five focal patches, which were typically 0.1–5.0 km apart within a single site. Movements between sites and patches might sometimes have reflected overwintering behaviour; however, similar movement patterns occurred at multiple times of the year, suggesting other factors were also involved. Use of multiple sites and patches might be driven by differences in resource availability, such as food and/or night‐time refuges, competition, or exploratory movement to investigate or locate alternative patches. We confirmed competition via direct visual observations of aggressive interactions between individuals at one foraging patch. Our results illustrate the importance of standardizing data to the same number of locations per day and night to accurately delineate key areas used by turtles or for evidence‐based marine protected area planning.  相似文献   

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