Fish and squid behaviour at the mouth of a drop-chain trawl: factors contributing to capture or escape

Abstract Underwater video recordings in the mouth of a squid trawl were used to evaluate the effectiveness of a trawl configured with drop-chain groundgear to catch longfin inshore squid (Doryteuthis pealeii) and reduce bycatch of finfish in the Nantucket Sound squid fishery off Cape Cod, Massachusetts, USA. Entrance through the trawl mouth or escape underneath the fishing line and between drop chains was quantified for targeted squid, and two major bycatch species, summer flounder (Paralichthys dentatus) and skates (family Rajidae). Additionally, contact and impingement between animals and groundgear were also quantified. Fish and squid swimming behaviours, positions, orientations, and time in the trawl mouth were quantified and related to capture or escape at the trawl mouth. Squid entered the trawl singly and in schools, and no squid were observed escaping under the fishing line. Most squid entered the trawl in the upper portion of the trawl mouth; mantle orientated away from the trawl and swimming in the same direction, and were gradually overtaken, not actively attempting to escape. Summer flounder and skates were observed to remain on or near the seabed, orientated, and swimming in the same direction as the approaching trawl. The majority (60.5%) of summer flounder entered the trawl above the fishing line. Summer flounder that changed their orientation and turned 180° were significantly more likely to enter the trawl (p < 0.05). Most skates (89.7%) avoided trawl entrance and escaped under the fishing line. Neither squid nor summer flounder were observed to make contact or become impinged to the groundgear; however, 35.4% of skates had substantial contact with groundgear, with 12.3% becoming impinged. Video analysis results showed that the drop-chain trawl is effective at retaining targeted squid while allowing skates to escape. However, it is ineffective at avoiding the capture of summer flounder.

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СИСТЕМЫ СТАЦИОНАРНОГО ПОДВОДНОГО ВИДЕОНАБЛЮДЕНИЯ ПРИБРЕЖНЫХ АКВАТОРИЙ

Podvodnye issledovaniia i robototehnika ◽

10.37102/24094609.2020.31.1.008 ◽

2020 ◽

Author(s):

V.K. Fishchenko ◽

P.S. Zimin ◽

A.V. Zatserkovnyy ◽

A.E. Subote ◽

A.V. Golik ◽

...

Keyword(s):

Marine Biology ◽

Surveillance Systems ◽

Underwater Video ◽

Vital Activity ◽

Geographically Dispersed ◽

Video Recordings ◽

Underwater Cameras ◽

The Pacific ◽

External Conditions ◽

Marine Vessels

В Тихоокеанском океанологическом институте (ТОИ) ДВО РАН с 2012 г. ведутся разработки и исследования возможностей технологий стационарного подводного видеонаблюдения. Развернуты три подводныхкомплекса: два в бухте Алексеева (о-в Попова) и один в бухте Витязь (зал. Посьета). К настоящему времени накоплены значительные объемы информации в виде моментальных снимков и видеозаписей подводныхсцен. Разработаны интерфейсы для предоставления этой информации пользователям по каналам сети Интернет. Разработаны технологии поддержки работы территориально разнесенных экспертов, составляющихбиологические описания видеоматериалов, подобных тем, которые разрабатываются в ведущих зарубежныхорганизациях по морской биологии. Разработаны и апробированы методики оценивания по видеоинформации параметров жизнедеятельности некоторых видов морских гидробионтов. Благодаря непрерывностинаблюдения зафиксировано нескольких редких случаев, представляющих интерес для морских биологов. Разработаны и апробированы методики оценивания гидрологических характеристик среды на основе анализавидеотрансляций с подводных камер. Эти результаты представляются важными в контексте сопровождениянаблюдений за жизнедеятельностью морской биоты данными о внешних условиях, в которых она происходит. Продемонстрирована возможность использования звукового канала камер для регистрации и анализаакустических шумов от морских судов. Продемонстрирована возможность применения подводных видеокомплексов для организации экспериментов по изучению реакции морских гидробионтов на воздействие целенаправленных физических сигналов.Since 2012, the Pacific Oceanological Institute of FarEastern Branch of the Russian Academy of Science has beendeveloping and studying the capabilities of technologies ofstationary underwater video surveillance. Three of the underwatercomplexes have been deployed in different waterareas: two in the Alekseev Bay (Popova Island) and one inVityaz Bay (Posyet Gulf). At this point, complexes have accumulateda significant amount of data in the form of snapshotsand video recordings of underwater scenes, which canbe accessed through designed Internet-based interfaces. Allthe surveillance systems contain technologies as a support ofthe work of geographically dispersed experts involved in thebiological description of video materials, similar to ones developedin leading worldwide marine biology organizations.Besides, the estimation of vital parameters of some marinelife species by the video recordings can be performed usingdeveloped and tested methods. Thanks to continuous observation,the designed systems have already recorded severalrare cases of interest for marine biologists. Hydrologicalcharacteristics of surrounding media can be studied usingdeveloped and tested methods of analysis of video streamingfrom underwater cameras. These results are especially crucialfor accompanying observations of the vital activity ofmarine organisms with data on external conditions in whichthey occur. Cameras built-in audio channels can be used forrecording and analyzing noises of marine vessels. Designedunderwater video complexes provide an opportunity forconducting experiments on studying the reaction of marineorganisms to dedicated physical signals.

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Understanding historical summer flounder (Paralichthys dentatus) abundance patterns through the incorporation of oceanography-dependent vital rates in Bayesian hierarchical models

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/cjfas-2018-0092 ◽

2019 ◽

Vol 76 (8) ◽

pp. 1275-1294 ◽

Cited By ~ 3

Author(s):

Cecilia A. O’Leary ◽

Timothy J. Miller ◽

James T. Thorson ◽

Janet A. Nye

Keyword(s):

Population Dynamics ◽

Gulf Stream ◽

Stock Assessment ◽

Deviance Information Criterion ◽

Information Criterion ◽

Natural Mortality ◽

Vital Rates ◽

Summer Flounder ◽

Paralichthys Dentatus ◽

Abundance Patterns

Climate can impact fish population dynamics through changes in productivity and shifts in distribution, and both responses have been observed for many fish species. However, few studies have incorporated climate into population dynamics or stock assessment models. This study aimed to uncover how past variations in population vital rates and fishing pressure account for observed abundance variation in summer flounder (Paralichthys dentatus). The influences of the Gulf Stream Index, an index of climate variability in the Northwest Atlantic, on abundance were explored through natural mortality and stock–recruitment relationships in age-structured hierarchical Bayesian models. Posterior predictive loss and deviance information criterion indicated that out of tested models, the best estimates of summer flounder abundances resulted from the climate-dependent natural mortality model that included log-quadratic responses to the Gulf Stream Index. This climate-linked population model demonstrates the role of climate responses in observed abundance patterns and emphasizes the complexities of environmental effects on populations beyond simple correlations. This approach highlights the importance of modeling the combined effect of fishing and climate simultaneously to understand population dynamics.

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Metamorphosis in the summer flounder Paralichthys dentatus: changes in gill mitochondria-rich cells

Journal of Experimental Biology ◽

10.1242/jeb.202.18.2475 ◽

1999 ◽

Vol 202 (18) ◽

pp. 2475-2484

Author(s):

A.M. Schreiber ◽

J.L. Specker

Keyword(s):

Larval Development ◽

Salinity Tolerance ◽

Stages Of Development ◽

Summer Flounder ◽

Physiological Mechanisms ◽

Paralichthys Dentatus ◽

Gill Mitochondria ◽

Dark Staining ◽

Dense Matrices ◽

Light Staining

Salinity tolerance changes during larval development and metamorphosis in the summer flounder (Paralichthys dentatus) and other teleosts. The physiological mechanisms responsible for osmoregulation during these early stages of development are not well understood. This study characterized changes in ultrastructure, intracellular membranes and immunoreactive Na(+)/K(+)-ATPase of mitochondria-rich cells (MRCs) in the gills of summer flounder during metamorphosis. Gill ultrastructure at the start of metamorphosis revealed only one type of MRC, which had weak reactivity to osmium and lacked a well-defined apical pit. In juveniles, two types of MRCs were observed: light-staining MRCs (LMRCs) with weak reactivity to osmium, and dark-staining MRCs (DMRCs) with strong reactivity to osmium and positioned adjacent to LMRCs. Compared with MRCs at the start of metamorphosis, the mitochondria of juvenile MRCs appeared smaller, with more transverse cristae and electron-dense matrices. Changes in MRCs during metamorphosis were also accompanied by increased immunoreactive Na(+)/K(+)-ATPase. These findings suggest that gill MRCs develop during the metamorphosis of summer flounder as the gill takes on an increasingly important osmoregulatory role.

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