Dataset: sublegal cod survival

Name: Survival of sub-legal cod with different handling methods from Fishing Vessels NEC-JP2003-1 in the Gulf of Maine from 2004-2006 (NEC-CoopRes project)
Published: 2011-12-06
Keywords: oceans

Cite This Dataset

Project:

Northeast Consortium: Cooperative Research (NEC-CoopRes)

Program:

NorthEast Consortium (NEC)

Principal Investigator:

John Pappalardo (Cape Cod Commercial Fishermen's Alliance, CCCFA)

BCO-DMO Data Manager:

Nancy Copley (Woods Hole Oceanographic Institution, WHOI BCO-DMO)

Version:

final

Version Date:

2011-12-06

Validated:

Yes

Current State:

Final no updates expected

Survival of sub-legal cod with different handling methods from Fishing Vessels NEC-JP2003-1 in the Gulf of Maine from 2004-2006 (NEC-CoopRes project)

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Description

Principle Investigators:

T. Rudolph
J. Pappalardo
M. Sanderson

Cape Cod Commercial Hook Fishermen's Association, 210E Orleans Road, North Chatham, MA 02650, USA [tel: 508 945 2432, fax: 508 945 0981 e-mail: tom@ccchfa.org, johnp@ccchfa.org and mel@ccchfa.org]

H.O. Milliken

NOAA / NMFS / NEFSC, 166 Water Street, Woods Hole, Massachusetts 02543, USA [tel: +1 508 495 2294, fax: 508 495 2066, e-mail: Henry.Milliken@noaa.gov].

M. Farrington

1 Algonquin Rd, Acton,e-mail:mfarr15@verizon.net].

Federal fisheries regulations require that undersized individuals of commercially important species be returned to the sea and the National Marine Fisheries Service (NMFS) has listed investigations into discard mortality rates as a research priority. For demersal longline fisheries, survival of discarded bycatch is uncertain. Sub-legal sized fish can incur injuries in their mouth, gills, and eyes and sometimes in the gut from hooks, as well as undergo pressure and temperature changes as they are brought to the surface. This study built on previous work that investigated the survival of sub-legal cod. The results of the previous study were hard to assess because of the large numbers of control fish that died. Additionally, the results of the previous study were questioned because the study was not conducted using commercial vessels. This study, funded by the Northeast Consortium (NEC), was executed in collaboration with commercial vessels fishing their commercial hook and line gear. Two handling techniques were examined and compared to jigged fish that acted as the control to estimate cage induced mortality. Longline caught fish were either removed from the hook by hand (unsnubbed) or removed by allowing the hydraulic hauler to pull the fish against the parallel steel cylinders placed vertically on the gunwale, causing the hook to pull through the jaw (snubbed). At the extreme, this process can result in breaking the jaw. This study was a cooperative effort between fishermen and scientists using standard commercial fishing practices. 3,764 sub-legal cod were assessed for survival at three different depth ranges and four sea surface temperature ranges. Survival, assessed after holding the fish in cages for a minimum of 72 hours, ranged from 30.8% to 100%. Binomial logistical regression analysis indicated that depth, sea surface temperature, and de-hooking technique all affected survival. Depth and temperature affected survival more than the de-hooking technique. Survival improved as depth and sea surface temperatures decreased. Unsnubbed fish had less mortality compared to snubbed fish. (from final report abstract)

Methods & Sampling

For each sampling event, defined as a day on which actual fishing took place, two to four vessels utilized commercial bottom set longline gear and rod and reel to target cod. After capture, sub-legal cod (<22 inches) were evaluated and held in on-board live wells until 50 fish had been collected, constituting a replicate, and the vessel was prepared for caging. The fish were then lowered to the seafloor in cages that were retrieved and evaluated after at least 72 hours. Fishermen were responsible for determining suitable experimental fishing areas within each required season-depth strata.

Strata: Fish were collected during the winter, spring, summer and fall seasons.The main variable of concern from season to season was sea surface temperature and therefore aimed to sample in each of four temperature categories as follows:
Cold         (<= 43 F)
Cool         (44-48 F)
Warm         (49-58 F)
Hot             (> 58 F)

The study was also designed to assess survival across different capture depths, and to investigate the interplay between season and depth. The statement of work called for sampling to take place in 20, 30, and 40 fathoms. This range represents the depths where most regional longline fishing occurs (J. Pappalardo, P. Comm.). The only change to the protocol in this respect was to treat these categories as ranges as follows:
20 fathoms        15-25 fathoms
30 fathoms        25-35 fathoms
40 fathoms        35-45 fathoms

Treatments: Within each unique combination of season and depth, three different treatments were conducted: snubbed, unsnubbed, and jigged. Snubbed and unsnubbed were both taken off the demersal longline gear and were intended to duplicate as closely as possible the release (discard) conditions for normal commercial fishing. As such, these treatments were comprised of the first 50 fish caught off a given string regardless of condition. While dead fish might not be tanked or caged to avoid attracting scavengers, they were still counted as mortality towards the sample size. The jigged fish were intended to act as a control, which would indicate cage-induced mortality. As such, only strong fish with no major injuries were selected towards the 50 fish sample; dead, weak or injured fish were not used or counted.

For each season, a minimum of 150 sub-legal fish were targeted for each of the three treatments at each of the three different depths.

NOTE: The 6/21/04 fish suffered from lack of oxygen while held on deck (first warm water sampling). Subsequent samples had bubblers and ice packs to keep the deck water cool and oxygenated.

For in-depth details on sampling protocols, see the final report.

Data Files

File
sublegal_cod.csv (Comma Separated Values (.csv), 1.82 KB) MD5:e5427140fd09cf9c796b7cf23ac6509f Primary data file for dataset ID 3582

More Information about this dataset

Funding Sources

Funding Source	Award Number
NorthEast Consortium	04-827

Deployments

Deployment	Synonyms	Start Date	Platform	Investigator
NEC-JP2003-1		2004-06-09	Fishing Vessels	John Pappalardo (Lead Principal Investigator) Marianne Farrington (Principal Investigator) Henry O. Milliken (Principal Investigator) Thomas Rudolph (Principal Investigator) Melissa Sanderson (Principal Investigator)	data info

Instruments

Fish Cage

Supplied Description:

A rigid low-rise cage with a cylindrical shape and integrated bottom weights, two feet high by four feet in diameter.

Instrument Type

Generic Name: Fish Cage

Community Identifier: http://vocab.nerc.ac.uk/collection/L05/current/90/

Generic Description:

Used to catch fish.

Fishing Rod

Supplied Description:

Instrument Type

Generic Name: Fishing Rod

Community Identifier: http://vocab.nerc.ac.uk/collection/L05/current/90/

Generic Description:

Used to catch fish.

Longline Fishing Gear

Supplied Description:

Instrument Type

Generic Name: Longline Fishing Gear

Acronym: Longline

Community Identifier: http://vocab.nerc.ac.uk/collection/L05/current/90/

Generic Description:

Longlining employs a central fishing line that can range from one to 50 miles long; this line is strung with smaller lines of baited hooks, dangling at evenly spaced intervals. Longlines can be set near the surface to catch pelagic fish like tuna and swordfish, or laid on the sea floor to catch deepdwelling fish like cod and halibut. (www.montereybayaquarium.org/cr/cr_seafoodwatch/sfw_gear.aspx)

Parameters

Date and time formats are described in python strftime() syntax.

Supplied Name	Supplied description	Supplied Units	Standard Name
method	method used to catch fish: jigged	snubbed or unsnubbed	no_bcodmo_term
temp_range	temperature range of water where fish were caught	degrees Fahrenheit	temp
yrday_local	local day and decimal time, as 326.5 for the 326th day of the year, or November 22 at 1200 hours (noon)	number	yrday_local
day_local	day of month	integer	day_local
month_local	month of year	integer	month_local
year	year of sampling	integer	year
depth_water_fthm	depth of fish capture; plus or minus 5 fathoms	fathoms	depth
alive	number of fish still alive after holding period	integer	no_bcodmo_term
dead	number of dead fish after holding period	integer	no_bcodmo_term
pcent_alive	survivorship; percent still alive after holding period	percent	no_bcodmo_term

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Database

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Dataset: sublegal cod survival