Effects of pot fishing on the physical condition of snow crab (Chionoecetes opilio) and southern Tanner crab (Chionoecetes bairdi)

The effects of commercial fishing with crab pots on the physical condition of the snow crab (Chionoecetes opilio) and southern Tanner crab (C. bairdi) were investigated in the Bering Sea and in Russian waters of the Sea of Okhotsk. In crabs that were subjected to pot hauling, the presence of gas embolism and the deformation of gill lamellae were found in histopathological investigations. Crab vitality, which was characterized subjectively through observation of behavioral responses, depended on not only the number of pot hauls but also the time between hauls. Immediately after repeated pot hauls at short time intervals (≤3 days), we observed a rapid decline in vitality of crabs. When hauling intervals were increased to >3 days, the condition of crabs did not significantly change. After repeated pot hauls, concentration of the respiratory pigment hemocyanin ([Hc]) was often lower in the hemolymph of crabs than in the hemolymph of freshly caught animals. Our research indicated that changes in [Hc] in crabs after repeated pot hauls were caused by the effects of decompression and not by starvation of crabs in pots or exposure of crabs to air. We suggest that the decrease in [Hc] in hemolymph of snow and southern Tanner crabs was a response to the adverse effects of decompression and air-bubble disease. The decrease in [Hc] in affected crabs may be a result of mechanisms that regulate internal pressure in damaged gills to optimize respiratory circulation.

The distribution of larval fishes of the Charleston Gyre Region off the southeastern United States in winter shaped by mesoscale, cyclonic eddies

Serial, cyclonic, mesoscale eddies arise just north of the Charleston Bump, a topographical rise on the continental slope and Blake Plateau, and characterize the U.S. outer shelf and upper slope in the region of the Charleston Gyre. This region was transected during the winters of 2000, 2001, and 2002, and hydrographic data and larval fishes were collected. The hydrodynamics of the cyclonic eddies of the Charleston Gyre shape the distribution of larval fishes by mixing larvae from the outer continental shelf and the Gulf Stream and entraining them into the eddy circulation at the peripheral margins, the wrap-around filaments. Over all years and transects (those that intercepted eddies and those that did not), chlorophyll a concentrations, zooplankton displacement volumes, and larval fish concentrations were positively correlated. Chlorophyll a concentrations were highest in filaments that wrapped around eddies, and zooplankton displacement volumes were highest in the continental shelf–Gulf Stream–frontal mix. Overall, the concentration of all larval fishes declined from inshore to offshore with highest concentrations occurring over the outer shelf. Collections produced larvae from 91 fish families representing continental shelf and oceanic species. The larvae of shelf-spawned fishes—Atlantic Menhaden Brevoortia tyrannus, Round Herring Etrumeus teres, Spot Leiostomus xanthurus, and Atlantic Croaker Micropogonias undulatus—were most concentrated over the outer shelf and in the continental shelf–Gulf Stream–frontal mix. The larvae of ocean-spawned fishes—lanternfishes, bristlemouths, and lightfishes—were more evenly dispersed in low concentrations across the outer shelf and upper slope, the highest typically in the Gulf Stream and Sargasso Sea, except for lightfishes that were highest in the continental shelf–Gulf Stream–frontal mix. Detrended correspondence analysis rendered groups of larval fishes that corresponded with a gradient between the continental shelf and Gulf Stream and Sargasso Sea. Eddies propagate northeastward with a residence time on the outer shelf and upper slope of ∼1 month, the same duration as the larval period of most fishes. The pelagic habitat afforded by eddies and fronts of the Charleston Gyre region can be exploited as nursery areas for feeding and growth of larval fishes within the southeastern Atlantic continental shelf ecosystem of the U.S. Eddies, and the nursery habitat they provide, translocate larvae northeastward.

MDNR-NOAA trawl standardization study

Long-term living resource monitoring programs are commonly conducted globally to evaluate trends and impacts of environmental change and management actions. For example, the Woods Hole bottom trawl survey has been conducted since 1963 providing critical information on the biology and distribution of finfish and shellfish in the North Atlantic (Despres-Patango et al. 1988). Similarly in the Chesapeake Bay, the Maryland Department of Natural Resources (MDNR) Summer Blue Crab Trawl survey has been conducted continuously since 1977 providing management-relevant information on the abundance of this important commercial and recreational species. A key component of monitoring program design is standardization of methods over time to allow for a continuous, unbiased data set. However, complete standardization is not always possible where multiple vessels, captains, and crews are required to cover large geographic areas (Tyson et al. 2006). Of equal issue is technological advancement of gear which serves to increase capture efficiency or ease of use. Thus, to maintain consistency and facilitate interpretation of reported data in long-term datasets, it is imperative to understand and quantify the impacts of changes in gear and vessels on catch per unit of effort (CPUE). While vessel changes are inevitable due to ageing fleets and other factors, gear changes often reflect a decision to exploit technological advances. A prime example of this is the otter trawl, a common tool for fisheries monitoring and research worldwide. Historically, trawl nets were constructed of natural materials such as cotton and linen. However modern net construction consists of synthetic materials such as polyamide, polyester, polyethylene, and polypropylene (Nielson et. al. 1983). Over the past several decades, polyamide materials which will be referred to as nylon, has been a standard material used in otter trawl construction. These trawls are typically dipped into a latex coating for increased abrasion resistance, a process that is referred to as “green dipped.” More recently, polyethylene netting has become popular among living resource monitoring agencies. Polyethylene netting, commonly known as sapphire netting, consists of braided filaments that form a very durable material more resistant to abrasion than nylon. Additionally, sapphire netting allows for stronger knot strength during construction of the net further increasing the net’s durability and longevity. Also, sapphire absorbs less water with a specific gravity near 0.91 allowing the material to float as compared to nylon with specific gravity of 1.14 (Nielson et. al. 1983). This same property results in a light weight net which is more efficient in deployment, retrieval and fishing of the net, particularly when towing from small vessels. While there are many advantages to the sapphire netting, no comparative efficiency data is available for these two trawl net types. Traditional nylon netting has been used consistently for decades by the MDDNR to generate long term living resource data sets of great value. However, there is much interest in switching to the advanced materials. In addition, recent collaborative efforts between MDNR and NOAA’s Cooperative Oxford Laboratory (NOAA-COL) require using different vessels for trawling in support of joint projects. In order to continue collaborative programs, or change to more innovative netting materials, the influence of these changes must be demonstrated to be negligible or correction factors determined. Thus, the objective of this study was to examine the influence of trawl net type, vessel type, and their interaction on capture efficiency.

Reproduction of blacknose shark (Carcharhinus acronotus) in coastal waters off northeastern Brazil

The blacknose shark, Carcharhinus acronotus, is a relatively small carcharinid, typically inhabiting continental shelf areas in the western Atlantic Ocean, from North Carolina throughout the Gulf of Mexico (Bigelow and Schroeder, 1948) and along the South American coast to Rio de Janeiro (Compagno, 1984). The abundance of this shark in nearshore areas throughout its distribution makes it accessible to commercial fishing, mainly from inshore hook-and-line and gill-net fisheries (Trent et al., 1997; Mattos and Hazin1).

一氧化氮(NO)调节白皮松花粉管生长和细胞壁构建的研究

花粉管是种子植物受精过程中的雄性生殖单位载体，具有典型的顶端极性生长特点，因此成为近年来研究植物细胞间相互识别、胞内外信号传递的模式系统。裸子植物花粉管与被子植物花粉管相比具有萌发时间长、生长缓慢等特点。一氧化氮（NO）作为一个重要的胞内信号分子，参与调节植物生长发育和多种生理过程，但是，有关NO对花粉管生长的作用机制目前尚不清楚。本研究以裸子植物白皮松(Pinus bungeana)花粉为材料，应用不同浓度的NO释放剂SNAP和SNP, NO清除剂cPTIO和哺乳动物一氧化氮合酶抑制剂L-NNA处理，对白皮松花粉萌发和花粉管伸长进行了细胞学研究，从而为进一步揭示NO调控裸子植物花粉管生长机理提供参考。 本论文首先研究了NO释放剂、清除剂及NOS抑制剂对白皮松花粉萌发和花粉管生长的影响。结果显示，SNAP和SNP能够促进白皮松花粉萌发和花粉管伸长，并具有浓度效用，但对其花粉管的形态特征无明显影响；cPTIO和L-NNA能够抑制白皮松花粉萌发和花粉管生长，并且具有浓度效应，同时还可使花粉管顶端膨大呈球形，并丧失花粉管的极性生长。运用NO特异探针DAF-2DA标记显示，SNAP和SNP处理可促进花粉管胞内NO产生；经cPTIO和L-NNA处理后，花粉管内荧光强度比对照花粉管明显减弱。上述结果表明，NO参与裸子植物花粉管极性生长，并且适量NO可以促进花粉管的生长。 用显微注射技术将Ca2+特异探针注射入白皮松花粉管，以检测白皮松花粉管胞内Ca2+浓度梯度。结果显示，SNAP和SNP处理后，NO荧光增加的同时，花粉管顶端Ca2+浓度梯度增加。与此相反，cPTIO和L-NNA处理后，NO荧光降低的同时，花粉管顶端Ca2+浓度梯度也相应降低。应用非损伤微测技术测定花粉管胞外Ca2+内流，结果显示，SNAP和SNP促进胞外Ca2+内流，而cPTIO和L-NNA则抑制胞外Ca2+内流。据此，我们推测，在白皮松花粉管中，NO可能通过调节胞外Ca2+内流来调节胞内Ca2+浓度梯度，然而，我们不能排除在NO信号传递过程中，胞内Ca2+库可能影响胞内Ca2+浓度梯度。 通过微丝特异探针标记的白皮松花粉管显示，SNAP和SNP可使花粉管顶端细微丝束解聚，而cPTIO和L-NNA处理后，花粉管中微丝聚合，尤其在花粉管顶端形成粗的微丝束，并一直延伸到花粉管的最顶端。结合上述Ca2+结果，我们认为，经NO处理后，白皮松花粉管微丝骨架的动态变化，可能是通过Ca2+浓度来进行调控的。通过FM4-64探针标记显示，正常生长白皮松花粉管胞吞作用主要集中在顶端和亚顶端，并且形成倒“V”形的分布模式，SNAP与SNP处理后荧光分布模式与对照花粉管类似，但达到饱和所用时间相对较短；而L-NNA处理后顶端膨大丧失极性的花粉管，荧光分布在膨大花粉管靠近质膜的区域，未见倒“V”形分布模式；经L-NNA处理后，顶端没有膨大的花粉管，荧光几乎均匀分布于整个花粉管，并且L-NNA处理后达到饱和的时间较对照长。上述结果表明，适量NO能够促进白皮松花粉管胞吞。 免疫抗体标记技术分析发现，对照花粉管的酯化果胶质和AGPs都集中在顶端，酸性果胶质分布在侧壁，胼胝质均匀分布在整个花粉管壁上。L-NNA处理后的花粉管，在其顶端出现酸性果胶和酯化果胶，以及有胼胝质积累，而AGPs则分布在花粉管的基部。运用傅里叶红外光谱技术（Fourier Transform Infared Spectroscopy, FTIR）技术分析白皮松花粉管顶端细胞壁成分，结果显示，SNAP处理后花粉管顶端酯化果胶增加而酸性果胶降低；与之相反，经L-NNA处理后的花粉管，其顶端酯化果胶降低而酸性果胶增加。 综上所述，在白皮松花粉管中，NO促进胞外Ca2+内流，从而维持胞内Ca2+浓度梯度，进而影响花粉管顶端微丝骨架的组装，促进囊泡运输，使花粉管顶端酯化果胶累积，最终促进花粉管的正常生长。

Meristic and morphometric studies of Lactarius lactarius (Schneider), off Bombay coast

In Lactarius lactarius off the Bombay coast, the meristic features D VII, D2 I/22, A III/27 vert 23, Gill rakers 12 on lower and 8 on upper limb can be used to characterise the population. Morphometric studies show the positive allometric growth in various body parts of this species. Preanal region and the depth of body grow faster than the head.

Morphometry, length-weight relationship and food and feeding habits of Otolithoides biauritus (Cantor, 1850) of Bombay waters

Thirteen morphometric and seven meristic characters, length-weight relationship and food and feeding habits of Otolithoides biauritus of Bombay coast (Maharashtra, India) were studied. Compared morphometric characters revealed positive allometric growth and high correlation ("r" ranging 0.898 - 0.996) between each other. Meristic characters were observed to be B sub(vii), D sub(1) 8-10, D sub(2) 27-31, P 17-20, V 5-7 and 7-10. Number of gill rackers on the first left gill arch ranged from 15 to 19. Length-weight relationship for both sexes together worked out to be W = 0.026, L super(2.646). The species is a predator, feeding mainly on motile Acetes, small fish and Loligo in order of preference.

Studies on fish epidemics from Assam

Investigations conducted since July 1988 on ulcerative fish epidemics in Assam, India, indicated that mainly four species of fishes belonging to the genera Puntius, Channa, Macrognathus and Mystus were widely affected by the disease. Results indicated that outbreak of the disease may not be due to organic pollution of water or radioactive and heavy-metallic contamination. Bacterial culture revealed colonies of Escherichia coli and Pseudomonas aeruginosa in the surface muscular lesions and gill tissues while preliminary electron microscopic studies indicated the presence of viruses in the muscles and gills of diseased fishes.

Characteristics of capture fishery resources, their assessment and management

There are two groups of factors, namely fishery independent factors such as current, temperature and salinity and fishery dependent factors such as types of fishing, namely trawling, gill netting etc. with different mesh sizes and intensity of fishing indicating the number of units of each type of fishing. Hence assessment of capture fishery resources remains a puzzle even today. However, attempts have been made to develop suitable mathematical and statistical models for assessing them and for offering suggestions for judicious management of the resources. This paper indicates in brief the important characteristics of the capture fisheries, their assessment and management with particular reference to India.