Age and growth estimates of the winter skate Age and growth estimates of the winter skate (Le(Leucoraja ocellata)ucoraja ocellata) in the western Gulf of Maine in the western Gulf of Maine

西緬因灣眼斑鰩年齡與成長評估西緬因灣眼斑鰩年齡與成長評估

James A. Sulikowski Michael D. Morin Seung H. Suk W. Huntting HowellJames A. Sulikowski Michael D. Morin Seung H. Suk W. Huntting HowellFishery Bulletin.101:405–413 (2003).Fishery Bulletin.101:405–413 (2003).

指導教授 莊守正老師指導教授 莊守正老師

學生 陳婧綺學生 陳婧綺 學號學號 M95310001M95310001

Winter SkateWinter Skate

MorphologyMorphology DistributionDistribution BiologyBiology

© George Burgess

MorphologyMorphology

Disk rounded .Disk rounded . With many small dark sWith many small dark s

pots on upper surface, upots on upper surface, usually 1-4 ocelli .sually 1-4 ocelli .

Young have long middorYoung have long middorsal row of large spines osal row of large spines on disk and tail. n disk and tail.

© James Sulikowski

www.osl.gc.ca/.../poiss/sp/images/l-ocellata.jpg

DistributionDistribution

Western Atlantic: Newfoundland Banks and soutWestern Atlantic: Newfoundland Banks and southern Gulf of St. Lawrence in Canada to North Cahern Gulf of St. Lawrence in Canada to North Carolina, USA .rolina, USA .

http://fishbase.fishinfo.cn/Summary/SpeciesSummary.php?id=2562

BiologyBiology

Prefer sandy and gravelly Prefer sandy and gravelly bottoms in shoal water in bottoms in shoal water in the north range .the north range .

Mostly inactive during dayMostly inactive during daylight hours, but active undlight hours, but active under dark conditions .er dark conditions .

Distinct pairing with embrDistinct pairing with embrace. Young may tend to face. Young may tend to follow large objects, such ollow large objects, such as their mother .as their mother .

http://www.osc.mun.ca/oscpictures/container/Harbour%20Main%20April%2018,%202005/target11.html

IntroductionIntroduction

Little is known about the biology of many eLittle is known about the biology of many elasmobranchs’ life history. lasmobranchs’ life history.

Difficulty in obtaining samples.Difficulty in obtaining samples.Recent assessment studies suggest that tRecent assessment studies suggest that t

he biomass of the winter skate maybe belohe biomass of the winter skate maybe below threshold-levels, mandated by the Sustaw threshold-levels, mandated by the Sustainable Fisheries Act.inable Fisheries Act.

To add insight into the life history of the spTo add insight into the life history of the species and the status of the stock, we estimecies and the status of the stock, we estimated age and growth rates of ated age and growth rates of L.ocellataL.ocellata by by interpreting annular counts and marginal ininterpreting annular counts and marginal increments on vertebral centra from specimcrements on vertebral centra from specimens collected in the western Gulf of Maine.ens collected in the western Gulf of Maine.

Materials and MethodsMaterials and Methods

SamplingSampling Sampling period: November 1999 and May 2001.Sampling period: November 1999 and May 2001. Sampling amount: 304.Sampling amount: 304. Sampling site: New Hampshire’ coast.Sampling site: New Hampshire’ coast. Approximate depth: 9-107m.Approximate depth: 9-107m. Captured by otter trawlCaptured by otter trawl Total length, disc width, and total wet weight werTotal length, disc width, and total wet weight wer

e measured and recorded.e measured and recorded.

Preparation of vertebral samplesPreparation of vertebral samples

Vertebral samples, Vertebral samples, taken from above the taken from above the abdominal cavity, abdominal cavity, were removed from were removed from 230 winter skates 230 winter skates (132 females and 98 (132 females and 98 males) labeled, and males) labeled, and stored frozen. stored frozen.

Counts of annuliCounts of annuli

IAPE(IAPE( 平均百分誤差指數平均百分誤差指數 ))

N= the number of skate agedN= the number of skate aged R= the number of readingsR= the number of readings XXijij= the = the iith age determination of the th age determination of the jjth fish th fish

XXjj= the average calculated for the = the average calculated for the jjth fishth fish

Marginal increment analysesMarginal increment analyses

D: D: 椎徑椎徑 DDnn: : 脊椎骨最外輪之輪 脊椎骨最外輪之輪 DDn-1n-1:: 脊椎骨次外輪之輪徑脊椎骨次外輪之輪徑 Kruskal-Wallis one-way analysis of variance on ranks Kruskal-Wallis one-way analysis of variance on ranks

was used to test for differences in marginal increment was used to test for differences in marginal increment by month.by month.

1

nn

n

dd

dD

1

nn

n

dd

dD

Growth estimatesGrowth estimates

A von Bertalanffy growth function (VBGF) was fitted to the A von Bertalanffy growth function (VBGF) was fitted to the data with the following equation (von Bertalanffy, 1938):data with the following equation (von Bertalanffy, 1938):

where Lwhere Lt t = total length at time t (age in years)= total length at time t (age in years)

LL∞∞= theoretical asymptotic length= theoretical asymptotic length

k = Brody growth constantk = Brody growth constant

tt00 = theoretical age at zero length (minus) = theoretical age at zero length (minus)

ResultsResults

Morphology measurementsMorphology measurements

（ｍｍ） （ｍｍ） （ｍｍ） （ｍｍ） （ｍｍ）

Vertebral analysesVertebral analyses

Age and growth estimatesAge and growth estimates

Males: L∞ = 1218 mm (TL).Males: L∞ = 1218 mm (TL). Females: L∞ = 1374 mm (TL).Females: L∞ = 1374 mm (TL).

IAPE=5.8%IAPE=5.8%

The oldest age estimates obtained for the winter The oldest age estimates obtained for the winter skate were 19 and 18 years for males and femalesskate were 19 and 18 years for males and females

DiscussionDiscussion The important of IAPEThe important of IAPE The relationship between TL and centrumThe relationship between TL and centrum diameter was linear and significant, indicating thdiameter was linear and significant, indicating th

at the centra grew proportionally to skate length fat the centra grew proportionally to skate length for all size classes, and thus this structure was usor all size classes, and thus this structure was useful for age analyses. eful for age analyses.

Holden(1977), Warning(1984), Ryland and AjayiHolden(1977), Warning(1984), Ryland and Ajayi(1984), Brander (1981)and Walmsley-Hart et al.(1984), Brander (1981)and Walmsley-Hart et al.(1999) found similar temdencies in several speci(1999) found similar temdencies in several species of skates and Martin and Cailliet(1988) found es of skates and Martin and Cailliet(1988) found comparable results in the bat ray(comparable results in the bat ray(MyliobatisMyliobatis califcalifornicaornica).).

..

ConclusionConclusion

Our study provides some basic age and groOur study provides some basic age and growth parameters for the winter skate and it swth parameters for the winter skate and it supports the hypothesis that upports the hypothesis that L. ocellataL. ocellata, like , like other elasmbranchs, require conservative mother elasmbranchs, require conservative management because they grow slowly and aanagement because they grow slowly and are susceptible to overexploitation.re susceptible to overexploitation.

Thanks for your attentionThanks for your attention

IAPEIAPE

Kruskal-Wallis one way analysisKruskal-Wallis one way analysis)1(3_

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nnW )1(3_

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K-W one way(K-W one way( 無母數檢定無母數檢定 ):):

母體中取得隻隨機樣本大於等於母體中取得隻隨機樣本大於等於 33 不是常態分佈不是常態分佈 有序位類別有序位類別

K-W 檢定是提供我們檢定母體是否相同的另一統計法。

IAPE(IAPE( 平均百分誤差指數平均百分誤差指數 ))

N=N= 總樣本數總樣本數 R=R= 樣本重複計算之次數樣本重複計算之次數 XXijij== 第第 jj 個樣本於第個樣本於第 ii 次計數之輪紋數次計數之輪紋數 XXjj== 第第 jj 個樣本重複計數之平均輪紋個樣本重複計數之平均輪紋

補充問題補充問題

QQ ：反推算？：反推算？ANSWERANSWER ：：以體長或椎徑來推估相互值以體長或椎徑來推估相互值

QQ ：哪兩種檢定可以檢定硬骨魚之：哪兩種檢定可以檢定硬骨魚之體長椎徑關係？體長椎徑關係？

ANSWERANSWER ：：

1.1. 最大概似法〈最大概似法〈 Likelihooh functionLikelihooh function 〉〉可檢定可檢定硬骨魚之體長椎徑關係硬骨魚之體長椎徑關係

2.2. 先以先以 VBGEVBGE 推算雌雄之值再以推算雌雄之值再以 ANCOVAANCOVA 檢定檢定

y=a+bx

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QQ ：： SDSD 和和 SESE 之差別？之差別？ANSWERANSWER ：：SD (standard deviation)SD (standard deviation) 標準差即母體的標準標準差即母體的標準差 差 SE (standard error)SE (standard error) 標準誤即母體變異數不標準誤即母體變異數不

知知道的情況之下，或是我們用樣本變異數估計道的情況之下，或是我們用樣本變異數估計母體變異數的情況下，稱為母體變異數的情況下，稱為 SESE

0Winter skate  

Raja ocellata Raja ocellata 之分類系統表　之分類系統表　 脊椎動物亞門　脊椎動物亞門　 Subphylum VertebrataSubphylum Vertebrata

軟骨魚綱　軟骨魚綱　 ChondrichthyesChondrichthyes 板鰓亞綱　板鰓亞綱　 ElasmobranchiiElasmobranchii 鯆魮目　鯆魮目　 RajiformesRajiformes 鯆魮科　鯆魮科　 RajidaeRajidae 鰩屬　鰩屬　 RajaRaja 眼斑鰩　眼斑鰩　 Raja ocellataRaja ocellata 本魚種非台灣魚種本魚種非台灣魚種