Data from: Discovery of a multi-species shark aggregation and parturition area in the Ba Estuary, Fiji Islands

Sampling event Observation
最新版本 published by Southwestern Pacific Ocean Biogeographic Information System (OBIS) Node on 8月 2, 2024 Southwestern Pacific Ocean Biogeographic Information System (OBIS) Node
發布日期:
2024年8月2日
授權條款:
CC-BY 4.0

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DwC-A資料集 下載 102 紀錄 在 English 中 (21 KB) - 更新頻率: 無計畫更新
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說明

Population declines in shark species have been reported on local and global scales, with overfishing, habitat destruction and climate change posing severe threats. The lack of species-specific baseline data on ecology and distribution of many sharks, however, makes conservation measures challenging. Here we present a fisheries-independent shark survey from the Fiji Islands, where scientific knowledge on locally occurring elasmobranchs is largely still lacking despite the location’s role as a shark hotspot in the Pacific. Juvenile shark abundance in the fishing grounds of the Ba Estuary (north-western Viti Levu) was assessed with a gillnet- and longline-based survey from December 2015 to April 2016. A total of 103 juvenile sharks identified as blacktip Carcharhinus limbatus (n = 57), scalloped hammerhead Sphyrna lewini (n = 35), and great hammerhead Sphyrna mokarran (n = 11) sharks were captured, tagged, and released. The condition of umbilical scars (68 % open or semi-healed), mean sizes of individuals (± SD) (C. limbatus: 66.5 ± 3.8 cm, S. lewini: 51.8 ± 4.8 cm, S. mokarran 77.4 ± 2.8 cm), and the presence of these species over recent years (based on fishermen interviews), suggest that the Ba Estuary area is a critical habitat for multiple species that are classified as “Near Threatened” or “Endangered”. Specifically, the area likely acts as a parturition ground over the studied period, and potentially as a subsequent nursery area. We identified subareas of high abundance and found that temperature, salinity and depth acted as small-scale environmental drivers of shark abundance. The data suggests a tendency for species-specific spatial use, both horizontally (i.e. between sampling areas) and vertically (i.e. across the water column). These results enhance the understanding of shark ecology in Fiji and provide a scientific basis for the implementation of local conservation strategies that contribute to the protection of these threatened species.

資料紀錄

此資源sampling event的資料已發佈為達爾文核心集檔案（DwC-A），其以一或多組資料表構成分享生物多樣性資料的標準格式。 核心資料表包含 102 筆紀錄。

亦存在 2 筆延伸集的資料表。延伸集中的紀錄補充核心集中紀錄的額外資訊。 每個延伸集資料表中資料筆數顯示如下。

Event (核心)
102
ExtendedMeasurementOrFact 
961
Occurrence 
103

此 IPT 存放資料以提供資料儲存庫服務。資料與資源的詮釋資料可由「下載」單元下載。「版本」表格列出此資源的其它公開版本，以便利追蹤其隨時間的變更。

版本

以下的表格只顯示可公開存取資源的已發布版本。

如何引用

研究者應依照以下指示引用此資源。:

Vierus T, Gehig S, Brunnschweiler J M, Glaus K, Zimmer M, Marie A D, Rico C (2024). Data from: Discovery of a multi-species shark aggregation and parturition area in the Ba Estuary, Fiji Islands. Version 1.0. Southwestern Pacific Ocean Biogeographic Information System (OBIS) Node. Samplingevent dataset. https://nzobisipt.niwa.co.nz/resource?r=ba_estuary_sharks&v=1.0

權利

研究者應尊重以下權利聲明。:

此資料的發布者及權利單位為 Southwestern Pacific Ocean Biogeographic Information System (OBIS) Node。 This work is licensed under a Creative Commons Attribution (CC-BY 4.0) License.

GBIF 註冊

此資源尚未向GBIF註冊

關鍵字

Samplingevent; Observation

聯絡資訊

Tom Vierus
  • 出處 ●
  • 連絡人
  • Researcher
Leibniz Center for Tropical Marine Ecology
Bremen
DE
Stefan Gehig
  • 出處
  • Researcher
Leibniz Center for Tropical Marine Ecology
Bremen
DE
Juerg M. Brunnschweiler
  • 出處
  • Researcher
University of the South Pacific
  • PO Box 1168
Suva
FJ
Kerstin Glaus
  • 出處
  • Researcher
University of the South Pacific
  • PO Box 1168
Suva
FJ
Martin Zimmer
  • 出處
  • Researcher
University of Bremen
Bremen
DE
Amandine D. Marie
  • 出處
  • Researcher
University of the South Pacific
  • PO Box 1168
Suva
FJ
Ciro Rico
  • 元數據提供者 ●
  • 出處
  • Researcher
University of the South Pacific
  • PO Box 1168
Suva
FJ

地理涵蓋範圍

Ba Estuary, Viti Levu, Fiji

界定座標範圍 緯度南界 經度西界 [-17.465, 177.594], 緯度北界 經度東界 [-17.42, 177.694]

分類群涵蓋範圍

Sharks

Species Carcharhinus limbatus (Blacktip shark), Sphyrna lewini (Scalloped hammerhead shark), Sphyrna mokarran (Great hammerhead shark)

時間涵蓋範圍

起始日期 / 結束日期 2015-12-02 / 2016-04-18

取樣方法

Based on the results of a pilot survey, seven 1.13 km2 circular sampling areas in the immediate vicinity of the river mouth were selected. Each sampling area featured contrasting environmental features (e.g., depth, distance to mangroves, turbidity) and overlapped with areas that local fishermen identified as having higher shark abundances. Sampling areas 1–6 contained 10 sites each, and area 7 contained nine sampling sites.

研究範圍 The study was conducted in a shallow bay environment (depth < 15 m) in north-western Viti Levu, the main island of the Republic of Fiji. The sampled area around the Ba River mouth is part of a larger bay that is sheltered from the open sea by patches of fringing reefs and from the mainland by mangroves. The sea bottom predominantly consists of muddy substrate and seagrass beds. The area is under strong tidal influence, with a tidal range of approximately 2 m (www.tide-forecast.com, 2016). There is activity by artisanal and subsistence fishermen from surrounding villages in the estuary. While sharks are by tradition not explicitly targeted in fishing operations, they regularly occur as low-value bycatch.

方法步驟描述:

  1. The main shark-fishing survey was conducted on 26 days from December 2015 to April 2016. Bottom-set gillnets and longlines were set at depths ranging from 1 to 15 m in the seven sampling areas, with a total of 73 and 30 deployments, respectively. All deployments were carried out between 18:00 and 02:00 from a 7 m fiberglass boat with a 40 HP engine. Two assistants and a captain were present at all times. Bait used on longlines consisted predominantly of Indian mackerel (Rastrelliger kanagurta), and occasionally of red snapper (Lutjanus argentimaculatus), squid (Loligo sp.), and mullet (Mugil cephalus). Up to two gillnets (100 m length and 3 m width, ~10 cm mesh size) were deployed simultaneously with a soak time of 1–6 hr. To minimize animal stress and mortality, gillnets were regularly checked in intervals of 15–25 min. When feasible, a longline (75 m) with 27 hooks was additionally deployed at the same sampling sites to assess potential catch differences attributed to gear selectivity. Distance between gangions attached to the floater line varied from 2.4 to 2.8 m. Gangion length ranged between 0.6 and 3 m, with the last 0.5 m consisting of 1.5 mm steel wire and a baited 13″ circle hook. In total, fishing effort ranged from 6 to 10.36 hr (longline) and 15 to 23.08 hr (gillnet) per sampling area. Total soak time of gillnet and longline deployments varied from 30 min to 6 hr, and from 45 min to 3 hr, respectively. Sampling effort was intended to be uniformly distributed among the seven sampling areas and ranged from 24.5 to 33.3 hr/area (mean: 28 ± 3 hr/area).

引用文獻

  1. Vierus, Tom et al. (2019). Data from: Discovery of a multi-species shark aggregation and parturition area in the Ba Estuary, Fiji Islands [Dataset]. Dryad. https://doi.org/10.5061/dryad.77k3k6n
  2. Vierus, T., Gehrig, S., Brunnschweiler, J.M., Glaus, K., Zimmer, M., Marie, A.D. and Rico, C., 2018. Discovery of a multispecies shark aggregation and parturition area in the Ba Estuary, Fiji Islands. Ecology and Evolution, 8(14), pp.7079-7093. https://doi.org/10.1002/ece3.4230

額外的詮釋資料

marine, harvested by iOBIS

替代的識別碼 https://nzobisipt.niwa.co.nz/resource?r=ba_estuary_sharks