Use of catenary geometry to estimate hook depth during near-surface pelagic longline fishing

Theory versus practice

Patrick H. Rice, C. Phillip Goodyear, Eric D. Prince, Derke Snodgrass, Joseph E. Serafy

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

Management and conservation of many highly migratory fish species are based on population assessments that rely heavily on catch and effort data from the pelagic longline fishing industry. In 2003, we monitored hook time at depth for shallow-set commercial longlines (i.e., four hooks between surface buoys) targeting swordfish Xiphias gladius in the Windward Passage between Haiti and Cuba. We deployed temperature-depth recorders (TDRs) on about every 13th hook and attached them to branchlines just above the hook. Most TDRs were placed on branchlines that were predicted by catenary geometry to be at the deepest hook position between floats. Additional TDRs were also placed at the shallowest predicted hook position. We monitored 10 pelagic longline sets with a length (mean ± SE) of 44.9 ± 2.0 km. Time at depth for each TDR was binned into 5-m depth intervals. The expected bimodal distributions of hook time at depth were not observed; modes were 40 m for both the shallowest and deepest predicted hook positions. The majority of the hook depth distributions for shallow and deep hook positions achieved only 43% and 31%, respectively, of the depths predicted by catenary equations (i.e., <92 and <127 m). Individual TDRs were poor estimators of hook time at depth for other TDRs in the same catenary hook position during the same set (significant mean depth differences = 76.2-100%) and were even worse predictors of the depths fished during other sets (significant mean depth differences = 100%). Hook depth predictions based on catenary geometry drastically overestimated actual fishing depth in this study. These results indicate that the use of catenary geometry for estimating hook depth and subsequent vertical fishing effort is inadequate and fails to capture both within- and among-set variability, potentially resulting in biased stock assessments.

Original languageEnglish
Pages (from-to)1148-1161
Number of pages14
JournalNorth American Journal of Fisheries Management
Volume27
Issue number4
DOIs
StatePublished - Nov 1 2007
Externally publishedYes

Fingerprint

fishing
geometry
Xiphias gladius
temperature
Haiti
fishing industry
fish industry
stock assessment
fishing effort
Cuba
targeting
vertical distribution

ASJC Scopus subject areas

  • Aquatic Science

Cite this

Use of catenary geometry to estimate hook depth during near-surface pelagic longline fishing : Theory versus practice. / Rice, Patrick H.; Goodyear, C. Phillip; Prince, Eric D.; Snodgrass, Derke; Serafy, Joseph E.

In: North American Journal of Fisheries Management, Vol. 27, No. 4, 01.11.2007, p. 1148-1161.

Research output: Contribution to journalArticle

Rice, Patrick H. ; Goodyear, C. Phillip ; Prince, Eric D. ; Snodgrass, Derke ; Serafy, Joseph E. / Use of catenary geometry to estimate hook depth during near-surface pelagic longline fishing : Theory versus practice. In: North American Journal of Fisheries Management. 2007 ; Vol. 27, No. 4. pp. 1148-1161.
@article{56ed47e8c77f40bba1cd1e81df8b29d6,
title = "Use of catenary geometry to estimate hook depth during near-surface pelagic longline fishing: Theory versus practice",
abstract = "Management and conservation of many highly migratory fish species are based on population assessments that rely heavily on catch and effort data from the pelagic longline fishing industry. In 2003, we monitored hook time at depth for shallow-set commercial longlines (i.e., four hooks between surface buoys) targeting swordfish Xiphias gladius in the Windward Passage between Haiti and Cuba. We deployed temperature-depth recorders (TDRs) on about every 13th hook and attached them to branchlines just above the hook. Most TDRs were placed on branchlines that were predicted by catenary geometry to be at the deepest hook position between floats. Additional TDRs were also placed at the shallowest predicted hook position. We monitored 10 pelagic longline sets with a length (mean ± SE) of 44.9 ± 2.0 km. Time at depth for each TDR was binned into 5-m depth intervals. The expected bimodal distributions of hook time at depth were not observed; modes were 40 m for both the shallowest and deepest predicted hook positions. The majority of the hook depth distributions for shallow and deep hook positions achieved only 43{\%} and 31{\%}, respectively, of the depths predicted by catenary equations (i.e., <92 and <127 m). Individual TDRs were poor estimators of hook time at depth for other TDRs in the same catenary hook position during the same set (significant mean depth differences = 76.2-100{\%}) and were even worse predictors of the depths fished during other sets (significant mean depth differences = 100{\%}). Hook depth predictions based on catenary geometry drastically overestimated actual fishing depth in this study. These results indicate that the use of catenary geometry for estimating hook depth and subsequent vertical fishing effort is inadequate and fails to capture both within- and among-set variability, potentially resulting in biased stock assessments.",
author = "Rice, {Patrick H.} and Goodyear, {C. Phillip} and Prince, {Eric D.} and Derke Snodgrass and Serafy, {Joseph E.}",
year = "2007",
month = "11",
day = "1",
doi = "10.1577/M06-114.1",
language = "English",
volume = "27",
pages = "1148--1161",
journal = "North American Journal of Fisheries Management",
issn = "0275-5947",
publisher = "American Fisheries Society",
number = "4",

}

TY - JOUR

T1 - Use of catenary geometry to estimate hook depth during near-surface pelagic longline fishing

T2 - Theory versus practice

AU - Rice, Patrick H.

AU - Goodyear, C. Phillip

AU - Prince, Eric D.

AU - Snodgrass, Derke

AU - Serafy, Joseph E.

PY - 2007/11/1

Y1 - 2007/11/1

N2 - Management and conservation of many highly migratory fish species are based on population assessments that rely heavily on catch and effort data from the pelagic longline fishing industry. In 2003, we monitored hook time at depth for shallow-set commercial longlines (i.e., four hooks between surface buoys) targeting swordfish Xiphias gladius in the Windward Passage between Haiti and Cuba. We deployed temperature-depth recorders (TDRs) on about every 13th hook and attached them to branchlines just above the hook. Most TDRs were placed on branchlines that were predicted by catenary geometry to be at the deepest hook position between floats. Additional TDRs were also placed at the shallowest predicted hook position. We monitored 10 pelagic longline sets with a length (mean ± SE) of 44.9 ± 2.0 km. Time at depth for each TDR was binned into 5-m depth intervals. The expected bimodal distributions of hook time at depth were not observed; modes were 40 m for both the shallowest and deepest predicted hook positions. The majority of the hook depth distributions for shallow and deep hook positions achieved only 43% and 31%, respectively, of the depths predicted by catenary equations (i.e., <92 and <127 m). Individual TDRs were poor estimators of hook time at depth for other TDRs in the same catenary hook position during the same set (significant mean depth differences = 76.2-100%) and were even worse predictors of the depths fished during other sets (significant mean depth differences = 100%). Hook depth predictions based on catenary geometry drastically overestimated actual fishing depth in this study. These results indicate that the use of catenary geometry for estimating hook depth and subsequent vertical fishing effort is inadequate and fails to capture both within- and among-set variability, potentially resulting in biased stock assessments.

AB - Management and conservation of many highly migratory fish species are based on population assessments that rely heavily on catch and effort data from the pelagic longline fishing industry. In 2003, we monitored hook time at depth for shallow-set commercial longlines (i.e., four hooks between surface buoys) targeting swordfish Xiphias gladius in the Windward Passage between Haiti and Cuba. We deployed temperature-depth recorders (TDRs) on about every 13th hook and attached them to branchlines just above the hook. Most TDRs were placed on branchlines that were predicted by catenary geometry to be at the deepest hook position between floats. Additional TDRs were also placed at the shallowest predicted hook position. We monitored 10 pelagic longline sets with a length (mean ± SE) of 44.9 ± 2.0 km. Time at depth for each TDR was binned into 5-m depth intervals. The expected bimodal distributions of hook time at depth were not observed; modes were 40 m for both the shallowest and deepest predicted hook positions. The majority of the hook depth distributions for shallow and deep hook positions achieved only 43% and 31%, respectively, of the depths predicted by catenary equations (i.e., <92 and <127 m). Individual TDRs were poor estimators of hook time at depth for other TDRs in the same catenary hook position during the same set (significant mean depth differences = 76.2-100%) and were even worse predictors of the depths fished during other sets (significant mean depth differences = 100%). Hook depth predictions based on catenary geometry drastically overestimated actual fishing depth in this study. These results indicate that the use of catenary geometry for estimating hook depth and subsequent vertical fishing effort is inadequate and fails to capture both within- and among-set variability, potentially resulting in biased stock assessments.

UR - http://www.scopus.com/inward/record.url?scp=37749036203&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=37749036203&partnerID=8YFLogxK

U2 - 10.1577/M06-114.1

DO - 10.1577/M06-114.1

M3 - Article

VL - 27

SP - 1148

EP - 1161

JO - North American Journal of Fisheries Management

JF - North American Journal of Fisheries Management

SN - 0275-5947

IS - 4

ER -