A Study On The Conservation Strategy Of Sepiella Maindroni Resources Based On Spawning Attachment

Sepiella maindroni,one of the four traditional seafoods of the East China Sea,has been largely extinct since the beginning of the 21 st century due to over-exploitation and exploitation by human activities.Regular stocking measures have restored its resources to a certain extent,but still cannot meet the current needs of the resources themselves.As a medium-sized annual squid,Sepiella maindroni has a complex spawning behaviour-attaching its eggs to an attachment,without which the hatching rate of the eggs will be greatly reduced,thus affecting the replenishment of the resource.Therefore,research on spawning attachments is essential for the recovery and conservation of Sepiella maindroni resource.In this study,we investigated the habitat requirements for spawning,selected suitable terrestrial plants for spawning and designed different configurations of spawning substrates for indoor trials,and made recommendations on resource conservation strategies based on the concepts of green development and landscape ecology.The main findings of the study are as follows.1.A survey of environmental factors was carried out in 2018 for four seasons in the Zhongjieshan Islands Special Marine Protected Area,and the results were analysed in three main aspects: hydrological environment,sediment environment and biological environment.In terms of hydrological environment,the range of seawater temperature variation surveyed during spawning months was 14.03～18.67℃,with an average of17.16℃,which was generally higher compared to 33 years ago(11～21℃),mainly reflected in the fact that the spawning time of Sepiella maindroni was about 20 days earlier on average,and the effect of salinity on its spawning has not yet been seen;in terms of sediment environment,the content of fine sand,muddy sand,sandy mud and mud was analysed The sediment environment was analysed for the content of fine sand,muddy sand,sandy mud and mud,and the substrate type was found to be suitable for spawning by the Sepiella maindroni.The results of the six indicators of heavy metals(mercury,arsenic,cadmium,lead,zinc and chromium)also met the criteria for Class 1 sediment,and no effect of sediment on the spawning of Sepiella maindroni was observed;for the biological environment,the chlorophyll a variation in the spawning month survey ranged from 0.512 to 2.243μg/L,with an average of 1.287μg/L.The survey results showed that there was no potential threat of red tide.The annual seasonal survey found 69 and 104 species of phytoplankton and zooplankton respectively,with diatoms accounting for 65.22% of the total number of phytoplankton species and copepods accounting for 26.92% of the total number of zooplankton species,with no effect on the spawning of Sepiella maindroni seen.2.Based on the strict selection of the spawning attachment for the Sepiella maindroni,the Analytical Hierarchy Process was used to construct an index screening system,determine the weight of each index,initially screen 258 terrestrial plant species according to the index sea selection,and quantitatively screen 13 plant species from 11 families and11 genera.These were: Holly,Golden-leaved Maidenhair,Manchurian Bamboo,Purple Bamboo,Pale Bamboo,Saline Alkali Pine,Salt Pine,Tamarisk,Golden Bird,Pomegranate,Rhododendron,Six Paths Wood and Artemisia.The results of the indoor egg attachment tests showed that the plants with the best egg attachment results were the Tooth-leaved Holly,Golden-leaved Maidenhair,Manzanita and Rhododendron,all in the high egg attachment group.The study showed that Sepiella maindroni were selective in their egg attachment,with a greater affinity for plants soaked in squid water and with attached eggs,and a preference for plants with tough branches and stubborn stems.3.Four spawning substrates with different functions and configurations were designed and produced based on different concepts: retention spawning substrates(hexagonal),avoidance spawning substrates(rectangular bamboo baskets),roosting spawning substrates(square nest)and trapping spawning substrates(cross cylindrical).In the indoor trial conducted in July 2021,egg attachment results were in descending order of hexagonal,rectangular bamboo basket,cross-cylinder and square nest,and retention results were in order of hexagonal,square nest,cross-cylinder and rectangular bamboo basket.In terms of overall egg attachment,the squid water-soaked attachment base > the seawater-soaked attachment base > the un-soaked seawater attachment base.The study further verified the preference of Sepiella maindroni for the squid water-soaked spawning attachment substrate,which is selective for conformation and also provides a theoretical basis for outdoor application with some practicality.4.Based on the results of the indoor experiments,the following recommendations were made for the conservation of the Sepiella maindroni resources in the Zhongjieshan Islands Special Marine Protected Area:(1)To uphold the concept of green development and change the method of stocking from the traditional polyethylene rope hanging egg release to the affinity-type plant hanging egg release,and from the release of squid fertilized eggs to the release of fertilized eggs combined with the attachment substrate.(2)Strengthen the management and conservation of protected areas,firstly to protect the migratory pathways of the Sepiella maindroni,and secondly to carry out region-wide management and conservation in conjunction with relevant fisheries regulations to achieve long-term,high-quality development of the resource.(3)From the perspective of over-exploitation and use of natural resources by human activities,the concept of landscape ecology is introduced,and suggestions are made for the creation of habitat for the Sepiella maindroni through the method of landscape creation:(1)optimise the layout and design of spawning grounds in the natural sea area,so that the overall synergy can form a large-scale effect;(2)accelerate the construction of a landscape ecological monitoring network index system for this marine area,so as to provide basic data support for biological behaviour and other research;(3)carry out network analysis of communities and communities.Carry out network analysis of communities and neighborhoods to gradually achieve a win-win situation of harmonious development between people and the region.