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1.
Myotomal slow-oxidative muscle (SM) powers continuous swimming and generates heat needed to maintain elevated locomotor muscle temperatures (regional endothermy) in tunas. This study describes how the amount and distribution of myotomal SM increases with fish size and age in juvenile yellowfin tuna Thunnus albacares in relationship to the development of regional endothermy. In T. albacares juveniles 40–74 mm fork length (LF; n = 23) raised from fertilised eggs at the Inter-American Tropical Tuna Commission Achotines Laboratory in Panama and larger juveniles (118–344 mm LF; n = 5) collected by hook and line off of Oahu, Hawaii, USA, SM was identified by histochemical staining for the mitochondrial enzyme succinic dehydrogenase or by colour (in the two largest individuals). The cross-sectional area of myotomal SM at 60% LF, a position with maximal percentage of SM in larger T. albacares, increased exponentially with LF. The percentage of total cross-sectional area composed of SM at 60% LF increased significantly with both LF and age, suggesting that SM growth occurs throughout the size range of T. albacares juveniles studied. In addition, the percentage of SM at 60% LF that is medial increased asymptotically with LF. The increases in amount of SM and medial SM, along with the development of the counter-current heat-exchanger blood vessels that retain heat, allow larger tuna juveniles to maintain elevated and relatively stable SM temperatures, facilitating range expansion into cooler waters.  相似文献   
2.
Considerable uncertainty remains over how increasing atmospheric CO2 and anthropogenic climate changes are affecting open‐ocean marine ecosystems from phytoplankton to top predators. Biological time series data are thus urgently needed for the world's oceans. Here, we use the carbon stable isotope composition of tuna to provide a first insight into the existence of global trends in complex ecosystem dynamics and changes in the oceanic carbon cycle. From 2000 to 2015, considerable declines in δ13C values of 0.8‰–2.5‰ were observed across three tuna species sampled globally, with more substantial changes in the Pacific Ocean compared to the Atlantic and Indian Oceans. Tuna recorded not only the Suess effect, that is, fossil fuel‐derived and isotopically light carbon being incorporated into marine ecosystems, but also recorded profound changes at the base of marine food webs. We suggest a global shift in phytoplankton community structure, for example, a reduction in 13C‐rich phytoplankton such as diatoms, and/or a change in phytoplankton physiology during this period, although this does not rule out other concomitant changes at higher levels in the food webs. Our study establishes tuna δ13C values as a candidate essential ocean variable to assess complex ecosystem responses to climate change at regional to global scales and over decadal timescales. Finally, this time series will be invaluable in calibrating and validating global earth system models to project changes in marine biota.  相似文献   
3.
Climate change can affect marine and estuarine fish via alterations to their distributions, abundances, sizes, physiology and ecological interactions, threatening the provision of ecosystem goods and services. While we have an emerging understanding of such ecological impacts to fish, we know little about the potential influence of climate change on the provision of nutritional seafood to sustain human populations. In particular, the quantity, quality and/or taste of seafood may be altered by future environmental changes with implications for the economic viability of fisheries. In an orthogonal mesocosm experiment, we tested the influence of near‐future ocean warming and acidification on the growth, health and seafood quality of a recreationally and commercially important fish, yellowfin bream (Acanthopagrus australis). The growth of yellowfin bream significantly increased under near‐future temperature conditions (but not acidification), with little change in health (blood glucose and haematocrit) or tissue biochemistry and nutritional properties (fatty acids, lipids, macro‐ and micronutrients, moisture, ash and total N). Yellowfin bream appear to be highly resilient to predicted near‐future ocean climate change, which might be facilitated by their wide spatio‐temporal distribution across habitats and broad diet. Moreover, an increase in growth, but little change in tissue quality, suggests that near‐future ocean conditions will benefit fisheries and fishers that target yellowfin bream. The data reiterate the inherent resilience of yellowfin bream as an evolutionary consequence of their euryhaline status in often environmentally challenging habitats and imply their sustainable and viable fisheries into the future. We contend that widely distributed species that span large geographic areas and habitats can be “climate winners” by being resilient to the negative direct impacts of near‐future oceanic and estuarine climate change.  相似文献   
4.
Acanthopagrus latus, long considered a single valid Indo‐West Pacific Ocean species, characterized by having yellow pelvic, anal and caudal fins, is reviewed and separated into A. latus (east Asian shelf) and Acanthopagrus longispinnis (Bengal Bay), and three new species: Acanthopagrus morrisoni sp. nov. (north‐western Australia), Acanthopagrus arabicus sp. nov. [Middle East (except for the Red Sea) to coasts of Iran and Pakistan, and western Indian coast] and Acanthopagrus sheim sp. nov. (The Gulf). Although A. latus as redefined considerably varies in morphology and colouration, it can be recognized as a discrete east Asian endemic, with the following nominal species being junior synonyms: Chrysophrys auripes, Chrysophrys xanthopoda, Chrysophrys rubroptera and Sparus chrysopterus. Chrysophrys novaecaledoniae, known only from the holotype (type locality: Nouméa, New Caledonia), is a questionable junior synonym of A. latus, the lack of subsequent collections suggesting that the type locality is erroneous. Acanthopagrus longispinnis is differentiated from the other species in the complex by consistently having 12 dorsal‐fin spines and a much larger second anal‐fin spine, 21–26% (mean 23%) of standard length (LS) (v. 14–24%, mean 18–21% in the other four species). Acanthopagrus morrisoni sp. nov. has the entire caudal fin yellow with a wide black posterior margin (persisting in preserved specimens) and consistently 3 ½ scale rows between the fifth dorsal‐fin spine base and the lateral line. Acanthopagrus sheim sp. nov. has the pelvic, anal and lower caudal fins vivid yellow, with two (rarely three) small black blotches on the lower inter‐radial membranes between the spinous and soft dorsal‐fin rays. Acanthopagrus arabicus sp. nov. consistently has 4 ½ scale rows between the fifth dorsal‐fin spine base and the lateral line, whereas A. latus always has black streaks proximally on the inter‐radial membranes between the yellow anal‐fin rays. A neotype and lectotye, respectively, are designated for A. latus and A. longispinnis. The p‐distance (net nucleotide substitutions per site) of partial mitochondrial 16s ribosomal RNA genes (538 bp) among the above species (except A. longispinnis) and three other congeners (Acanthopagrus berda, Acanthopagrus pacificus and Acanthopagrus bifasciatus) strongly indicates that each is a distinct species. A key is provided for the 20 species of Acanthopagrus currently known from the Indo‐West Pacific Ocean.  相似文献   
5.
The functional significance of finlets on the steady swimming performance of yellowfin tuna Thunnus albacares was evaluated by measuring the speed and tail‐beat frequency of the fish with and without them. It was hypothesized that if finlets do improve swimming performance, fish without finlets would have to work harder to maintain the same swimming speed as fish with them and that this would be reflected in kinematic differences. Two‐way ANOVA showed significant effects between individuals on speed (d.f. = 5 and 228, P  < 0·001) and tail‐beat frequency (d.f. = 5 and 48, P  < 0·001), but no significant effects of treatment on speed (d.f. = 1 and 228, P  = 0·25) and tail‐beat frequency (d.f. = 1 and 48, P  > 0·1). No interaction effects on speed (d.f. = 5 and 228, P  > 0·1) and tail‐beat frequency (d.f. = 5 and 48, P  > 0·25) were found. This suggested that finlets were unlikely to function as significant drag reduction and thrust enhancing devices in routine steady swimming. Though not statistically significant, small percentage differences between the mean swimming speeds and tail‐beat frequency of the untreated and treated groups (fish with and without finlets respectively) of the order of 0·5% may be meaningful over the life of a fish. Also, finlets may improve performance at high sustained speeds in rapid accelerations and turns.  相似文献   
6.
The diet of harbor seals (Phoca vitulina richardii) in San Francisco Bay (SFB), California, was determined from July 2007 to July 2008 using prey hard parts recovered from 442 scats collected at five haul‐out sites. Twenty‐two species of fish and one species of crustacean were identified, but harbor seals primarily ate a nonnative invasive species, yellowfin goby (Acanthogobius flavimanus), which increased in dietary importance since the diet was last studied in 1991/1992. Additionally, another nonnative invasive fish species, chameleon goby (Tridentiger trigonocephalus), was found for the first time in the diet of harbor seals in SFB. Harbor seal diet was statistically different between years (1991/1992 and 2007/2008), between the pupping and nonpupping seasons, and between North SFB and South SFB haul‐out locations. The diet of harbor seals was significantly correlated with fish species caught in trawl surveys conducted by the California Department of Fish and Wildlife (CDFW) during the same time periods as this study (2007/2008). Harbor seals currently are influencing the health of the SFB ecosystem in a positive manner by consuming large quantities of nonnative invasive fish species.  相似文献   
7.
Data collected by scientific technicians aboard tuna purse seiners in the eastern Pacific Ocean since the early 1970s have allowed us to study the biology and herd dynamics of pelagic dolphins. A pattern of increasing group size in the morning and subsequent decline in the late afternoon or night was evident for spotted, spinner, and common dolphins, as well as for large yellowfin tuna that associate with dolphins. Diel patterns were also apparent in the formation of mixed-species herds of spotted and spinner dolphins and tuna-dolphin aggregations. Different patterns, however, were displayed by bottlenose dolphins and by yellowfin and skipjack tunas that did not associate with dolphins. It appears that these diel patterns are produced by an interaction of predation pressure and prey distribution.  相似文献   
8.
9.
Restriction fragment length polymorphism found in the S7 ribosomal protein gene introns of yellowfin tuna (Thunnus albacares) was compared between a single pair of parents and their offspring. The sizes of the first intron (RP1) and second intron (RP2) amplified by polymerase chain reaction were 810 bp and 1400 bp, respectively. The dam and sire had different restriction types from one another in HhaI and RsaI digestions for RP1 and in DdeI, HhaI, and ScrFI digestions for RP2. Putative genotypes in both introns of 64 larvae were found to be segregated in Mendelian proportions. Genotype distributions in a wild yellowfin tuna sample (n= 34) were in Hardy-Weinberg proportions, and observed heterozygosity ranged from 0.149 to 0.388. This study presents novel Mendelian markers, which are feasible for tuna population genetic study and pedigree analysis. Received December 8, 1999; accepted April 11, 2000.  相似文献   
10.
Fishborne trematode (FBT) metacercariae were investigated in yellowfin goby, Acanthogobius flavimanus, collected from Shinan-gun and Muan-gun, Jeollanam-do (province), Korea. All collected fishes were examined using the artificial digestion method. In all of 15 gobies from Aphae-myeon in Shinan-gun, metacercariae of Stictodora spp. (334 metacercariae/fish), Heterophyes nocens (153/fish), and Heterophyopsis continua (20/fish) were detected. In 2 of 14 gobies from Jido-myeon in Shinan-gun, 8 Echinostoma hortense metacercariae in total were detected. In 15 gobies from Haeje-myeon in Muan-gun, the metacercariae of H. continua were found in 100%, Stictodora spp. in 86.7%, and H. nocens in 6.7% of fish examined. The average numbers of metacercariae per infected fish were 23.3 (H. continua), 416.0 (Stictodora spp.), and 2.0 (H. nocens), respectively. The metacercariae of E. hortense found in gobies were elliptical, with 150 × 138 µm in average size, and had 27 collar spines on the head crown. The above results suggest that yellowfin gobies from 2 localities may be the potential infection sources of FBT. Moreover, it is proved for the first time that the yellowfin goby, A. flavimanus, acts as a second intermediate host for E. hortense.  相似文献   
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