Competitive interactions between native and exotic salmonids: a combined field and laboratory demonstration

Abstract –  We studied the impact of two exotic salmonid species (brook trout, Salvelinus fontinalis and rainbow trout, Oncorhynchus mykiss ) on native brown trout ( Salmo trutta fario ) habitat, growth and survival. Habitat selection and vertical distribution between young-of-the-year of the three species were examined in a stream aquarium under different sympatric and allopatric combinations. In addition, similar species combinations were introduced in a Pyrenean mountain stream (southwest France) in order to extend laboratory results to growth and apparent survival. Both laboratory and field results indicated that rainbow trout significantly affected native brown trout habitat selection and apparent survival. On the contrary, brown trout habitat, growth and apparent survival were hardly affected by brook trout. These results support the idea that rainbow trout negatively influence native brown trout, and that competition could influence the outcome of fish biological invasions in freshwater ecosystems.     

Competitive interactions among multiple non‐native salmonids and two populations of Atlantic salmon

Competitive interactions with non‐native species can have negative impacts on the conservation of native species, resulting in chronic stress and reduced survival. Here, juvenile Atlantic salmon (Salmo salar) from two allopatric populations (Sebago and LaHave) that are being used for reintroduction into Lake Ontario were placed into semi‐natural stream tanks with four non‐native salmonid competitors that are established in Ontario streams: brown trout (S. trutta), rainbow trout (Oncorhynchus mykiss), Chinook salmon (O. tshawytscha) and coho salmon (O. kisutch). Brown trout and rainbow trout reduced the survival and fitness‐related traits of Atlantic salmon, whereas Chinook salmon and coho salmon had no impact on these traits. These data support theories on ecological niche overlap and link differences in observed aggression levels with competitive outcomes. Measurements of circulating hormones indicated that the Atlantic salmon were not chronically stressed nor had a change in social status at the 10‐month time point in the semi‐natural stream tanks. Additionally, the Sebago population was better able to coexist with the non‐native salmonids than the LaHave population. Certain populations of Atlantic salmon may thus be more suitable for some environments of the juvenile stream phase for the reintroduction into Lake Ontario.     

Predation relationships between introduced salmonids and the native fish fauna in lakes and reservoirs in northern Patagonia

Abstract– A few native and exotic fish species are caught frequently in Andean lakes and reservoirs of northwestern Patagonia. Puyen ( Galaxias maculatus ) prey on zooplankton and benthos. Percichthys trucha has a wide range of prey, mainly benthos, while P. colhuapiensis become piscivorous when grown. Pejerrey ( Odonthestes hatcheri ) is omnivorous and large size individuals can be piscivorous. A siluroid, Diplomystes viedmensis , preys on benthos, insects, and fishes. Introduced salmonids are potential piscivorous. The puyen is the major prey category among fishes. Salmonids and perchichtids seem to partially overlap their diets but predation on Diplomystes appears to be restricted to salmonids. Present abundance of puyen, pejerrey and Percichthys spp. does not indicate a strong salmonid effect. However, the low abundance of D. viedmensis does. We studied present predation relationships among native and introduced fishes and postulated possible effects upon native fish fauna.     

The native South American crayfishes (Crustacea,Parastacidae): state of knowledge and conservation status

相似文献   

The growth and reproductive endocrinology of adult triploid Pacific salmonids

This paper describes the effect of triploidy on growth and reproductive endocrinology in the months leading up to and including spawning in rainbow trout,Salmo gairdneri, and pink salmon,Oncorhynchus gorbuscha. Growth rates were the same for diploid and triploid rainbow trout, but triploid female pink salmon were smaller than maturing diploid females and diploid and triploid males of the same age. Triploid males of both species developed typical secondary sexual characteristics and had normal endocrine profiles, although their cycle appeared to be delayed by about one month. Triploid females remained silvery in appearance and showed no endocrine signs of maturation, even at the level of the pituitary. Thus, although triploids of both sexes are genetically sterile, only the females do not undergo physiological maturation.Reported in part at the Third International Symposium on Reproductive Physiology of Fish, St. John's, Newfoundland, August 2–7, 1987.     

The disease status of Australian salmonids: bacteria and bacterial diseases

Abstract. Eleven freshwater salmonid hatcheries in southern Australia were surveyed for bacterial pathogens and diseases between 1981 and 1985, Twenty-five populations of fish were examined in the study, representing a total of 2755 fish, from which kidney, liver, spleen, and in some cases peritoneum, blood and faeces were cultured. Bacteria of pathogenic significance isolated included Aeromonas hvdrophila, Streptococcus sp., Lactobacillus piscicola, Yersinia ruckeri, Mycobacterium fortuitum, M. chelonei and a filamentous acid-fast organism of uncertain taxonomic position. Lacto-bacillus piscicola and Streptococcus sp. were associated with clinical and subclinical peritonitis. Mycobacterium chelonei was isolated from visceral granulomas in an externally normal fish. Aeromonas salmonicida, Renibacterium salmoninarum and Edwardsiella tarda were not isolated, indicating that the diseases furunculosis, bacterial kidney disease and edwardsiellosis are exotic to Australian salmonids. Similarly, while Y. ruckeri was isolated, enteric redmouth disease had not been recorded and is considered an exotic disease.     

Diet and trophic niche overlap of native and nonnative fishes in the Gila River,USA: implications for native fish conservation

Pilger TJ, Gido KB, Propst DL. Diet and trophic niche overlap of native and nonnative fishes in the Gila River, USA: implications for native fish conservation. Ecology of Freshwater Fish 2010: 19: 300–321. © 2010 John Wiley & Sons A/S Abstract –  The upper Gila River basin is one of the few unimpounded drainage basins west of the Continental Divide, and as such is a stronghold for endemic fishes in the region. Nevertheless, multiple nonindigenous fishes potentially threaten the persistence of native fishes, and little is known of the trophic ecology of either native or nonnative fishes in this system. Gut contents and stable isotopes (¹³C and ¹⁵N) were used to identify trophic relationships, trophic niche overlap and evaluate potential interactions among native and nonnative fishes. Both native and nonnative fishes fed across multiple trophic levels. In general, adult native suckers had lower ¹⁵N signatures and consumed more algae and detritus than smaller native fish, including juvenile suckers. Adult nonnative smallmouth bass (Micropterus dolomieu), yellow bullhead (Ameiurus natalis) and two species of trout preyed on small‐bodied fishes and predaceous aquatic invertebrates leading to significantly higher trophic positions than small and large‐bodied native fishes. Thus, the presence of these nonnative fishes extended community food‐chain lengths by foraging at higher trophic levels. Although predation on juvenile native fishes might threaten persistence of native fishes, the high degree of omnivory suggests that impacts of nonnative predators may be lessened and dependent on environmental variability.     

Habitat mapping and conservation analysis to identify critical streams for Arizona's native fish

• 1. Arizona's native fish species are among the most imperilled fauna in North America. Knowing the current distribution of native fish and their habitat is critical to their management and conservation, but the last detailed mapping effort was more than 30 years ago and pre‐dated computer mapping techniques.
• 2. Current distribution of 34 native fish species was modelled by identifying perennial stream segments for which species presence had been documented. A composite of these single‐species maps displays a pattern of species richness that can inform conservation, especially when overlaid with maps of management status or invasive species.
• 3. The map overlays suggest that conservation priorities should include Eagle Creek, the Verde River and its tributaries, Aravaipa Canyon, the Virgin River and Black Draw, which together hold 63% of native fish species. Of the 32 streams that support five or more native species, 28 have at least one non‐native fish species, indicating that a more aggressive programme of removing non‐natives may be critical to maintaining those native populations.
• 4. The U.S. Forest Service and Native American tribes administer the majority of occupied stream habitat (30% and 27%, respectively). While private lands hold the third‐highest amount of occupied habitat (19%), they control streams occupied by the greatest total number of native species (30). Conservationists should work more with private land owners, while also coordinating efforts with the U.S. Forest Service and North American tribes.
• 5. These data are publicly available (on the Internet, URL: www.azconservation.org ) to encourage refinement and use.

Copyright © 2006 John Wiley & Sons, Ltd.     

The disease status of Australian salmonids: viruses and viral diseases

Abstract. Eleven freshwater salmonid hatcheries in southern Australia were surveyed for the presence of viruses and viral diseases. Tissues from a total of 6025 fish of five salmonid species were cultured for viruses on RTG-2, BF-2 and FHM cell lines. No viruses were detected. The study strongly suggests that Australian salmonid populations are free of the cytopathic salmonid viruses. This virus-free status is of economic significance for the production and export of ova and other salmonid products, and deserves stringent quarantine protection.     

Cold-branding and fin-clipping for marking of salmonids

Identification of individual fish is important under many research circumstances and is essential in breeding and selection work. Results are presented from the marking system used at the Norwegian Research Station for Salmonids. Trained personnel and good light conditions are necessary to obtain a high percentage of correct identifications. The best result obtained was 99% identification 22–28 months after marking. It is estimated that 1.4% of the fish read were incorrectly identified. The frequency of misidentified fish was higher when different cold-branded symbols were included in the system, increasing to a mean of 8% for salmon and 15% for rainbow trout.Cold-branding using five different symbols at two of six different positions on the fish gives 600 permutations when used in conjuction with clipping of the adipose and right or left pelvic fins. A satisfactory degree of correct identification is possible for use in a programme of selection in salmonids.     

Farming of salmonids in Russia

Abstract. Salmonids of the genera Salmo and Oncorhynchus are the main aquaculture Interest of Russia. Culture of salmonids, as well as other species, is determined by two factors: vulnerability of coastal areas to storms and high temperatures in the south of Russia and long periods of icing and low temperatures in the north. Adaptation of salmonids to these conditions therefore is an important aspect of research in Russia.
The culture of salmonids in Russia can be divided into three categories:
(1) traditional hatchery rearing and release of fingerlings into natural populations;
(2) acclimatization of Pacific salmon through transoceanic transportation; and
(3) commercial production in sea cages.     

The use of small wire-mesh traps in sampling juvenile salmonids

Abstract. Sampling of juvenile salmonids is often difficult or impractical in deep pools or areas of dense cover. Small, wire-mesh ‘minnow’ traps can be used successfully in these conditions, however, and are now a standard sampling tool in the Pacific Northwest of North America. The use and application of the traps in studies of juvenile salmonids is discussed and an experimental study described in which the relationship between traps soak-time and catch size was investigated. In areas of high population density, catches of juvenile salmonids reached a peak after l-2h whereas in lower density areas catch continued to increase over 24h.     

Hybrids as potential mediators spreading non-native genes: Comparison of survival,growth, and movement among native,introduced and their hybrid salmonids

Comparing multiple fitness components and potential movement of wild hybrids with their parental species is necessary to fully understand the consequences of human-mediated introgression, but studies tracking both parental species and their hybrids at the individual-level are limited. Here, we compared growth, survival and movement of sympatric introduced brook trout (BT: Salvelinus fontinalis) and native white-spotted charr (WSC: S. leucomaenis) with their hybrids (HYB) in a northern Japanese stream, using mark-recapture data (1,087 marked individuals) collected over 4 years (2013–2016). The mark-recapture data with a single cohort showed that HYB had a comparable or even higher growth rate to BT and WSC. In addition, there is no evidence that hybrid survival was lower than both parental species throughout the entire study period. Furthermore, HYB showed high mobility equivalent to WSC, while BT showed the lowest mobility. Although our previous studies have documented the reduction of BT distribution and lowered reproductive success of HYB, non-native genes can pose a threat to native WSC via relatively high survival, growth and/or mobility of HYB.     

Hybridization in salmonids: Results and perspectives

This report presents a critical review of interspecific hybridization in salmonids and discusses the potentiality of hybrids for water management and fish farming.     

西北地区试养银鲑初报

银鲑原是一种海水鱼类 ,在美国经人工驯化后能够在淡水中养殖。近几年国内银鲑养殖仅限于北京地区几个有渔业外事关系的单位 ,其他省区没有养殖。本所 2 0 0 0年 5月 2 7日从北京康鑫水产公司引进银鲑试养 ,取得了良好的效果。1　苗种引进及放养5月 2 7日从北京康鑫水产公司 ,采用泡沫箱尼龙袋充氧加冰的方法 ,空运规格 7～ 8厘米的银鲑鱼苗 10 0 0尾 ,每箱装 2 50尾 ,运输时间 16小时 ,运输成活率 10 0 %。鱼苗运抵渔场后 ,先暂养在网箱中 ,投喂煮熟的鸡蛋黄 ,第 2天放入流水池塘。池塘面积 38平方米 ,水深 4 0厘米 ,养殖水为泉水 ,水温 10…     

The design and development of a life supporting system for experimenting on salmonids

This study concerns the development and the testing of a system which permits intensive rearing of aquatic animals. The system offers practical opportunities for various experimental situations, sufficient carrying capacity to allow statistical analysis, ease of operation, and insures the stability necessary for experimental interpretation. It has the advantages of being constructed at a low cost and of offering great flexibility. Experiments have been conducted for testing the system with the brook trout Salvelinus fontinalis, which have demonstrated its reliability. It is shown that structural and functional characteristics of this culturing system permit the underlining of aspects of growth and health which are difficult to analyze in similar studies.     

Pathogenicity of Vibrio harveyi to salmonids

Out of 19 Vibrio harveyi isolates obtained from a diversity of hosts and geographical locations, 14 were pathogenic to rainbow trout, Oncorhynchus mykiss (Walbaum), and Atlantic salmon, Salmo salar L., with mortalities of up to 100% following intraperitoneal injections of 106 cells fish?1. The extracellular products (ECPs) of only five pathogenic isolates were harmful to fish. Both pathogenic and non‐pathogenic cultures produced ECPs containing caseinase, gelatinase, phospholipase, lipase and haemolysins. Vibrio harveyi VIB 645, which was the most pathogenic isolate, produced ECPs with a maximal effect on salmonids from preparations obtained by using cellophane overlays on tryptone soya agar supplemented with 1% (w/v) sodium chloride with incubation at 28 °C for 24 h. This preparation contained the highest titre of haemolytic activity to Atlantic salmon (1:256) and rainbow trout (1:32) erythrocytes.