501
Marine and
Fishery Sciences
MAFIS
*
Improvements in length structure, reproductive indices, and spawning
biomass following strengthened sheries management: evidence from the
common sardine (Strangomera bentincki) o central-southern Chile
1
1
5
Eveling Monsalve Tequén Luis A. Cubillos
Sebastián I. Vásquez
ABSTRACT.
Stran-
gomera bentincki
Key words:
Mejoras en la estructura de talla, índices reproductivos y biomasa de desove tras el fortaleci-
miento de la gestión pesquera: evidencia de la sardina común (Strangomera bentincki) frente
a la costa centro-sur de Chile
RESUMEN.
Strangomera bentincki
Marine and Fishery Sciences 39 (4): 501-523 (2026)
Strangomera bentincki
<
>>
Palabras clave:
Monsalve Tequén et al.: Small pelagic fish demographic traits and fisheries management improvements
Open access Political
decisions
Scientific supported
decisions
Industrialfleet
operated within 5 n.mi Fully
exploited
regime
Maximum
limit for catch
ownership
Artisanal
Fishing
Register
Scientific Technical
Committee & Management
Committee
Management
plan
Discard law
Landings (t)
750,000
500,000
250,000
0
BA
1991 1994 1997 2000 2003 2006 2009 2012 2015 2018 2021
Year
Marine and Fishery Sciences 39 (4): 501-523 (2026)
Study area and data sources
Data analysis
post hoc
G
W
= �G�
WG
Monsalve Tequén et al.: Small pelagic fish demographic traits and fisheries management improvements 505
In addition, changes in the condition factor (CF)
were compared. It was computed for each spec-
imen as CF = 100 · WE/L3 where WE is the ob-
served eviscerated weight and L is the total length
(cm) of the sh (Fulton 1904). Data were obtained
from biological monitoring components of the Pe-
lagic Fisheries Monitoring Program of IFOP con-
ducted between 1991 and 2023.
Modeling changes in GSI and CF
To evaluate changes in reproductive activity and
body condition across management periods, the
GSI and CF were separately modeled using gen-
eralized linear mixed models tted with the glm-
mTMB package in R (Brooks et al. 2017). Because
both response variables were positive and right-
skewed, models were tted assuming a Gamma
error distribution with a log-link function (see Ap-
pendix for statistical details). Management periods
were included as a xed eect. Seasonality was
represented using Fourier terms based on calendar
month, allowing seasonal patterns to dier among
management periods. Fish length was included as a
covariate using a natural cubic spline to account for
non-linear eects, and a season × length interaction
was incorporated because reproductive investment
and body condition may vary seasonally with sh
size (see Appendix for details). Temporal depend-
ence among monthly observations was modeled
using a rst-order autoregressive (AR1) structure
at the month-year level within each management
period. Four nested candidate models were com-
pared using ΔAIC, residual diagnostics, and biolog-
ical interpretability (Burnham and Anderson 2002).
The nal model was selected when it minimized
AIC, showed no relevant residual autocorrelation,
and adequately represented seasonal and size-re-
lated patterns.
Spawning biomass, recruitment, and shing
mortality
Fishing mortality (F), spawning biomass (SSB),
and recruitment among management periods were
compared using Kruskal-Wallis and Dunn’s post
Table 1. Chronology of sheries regulations and management aecting the common sardine shery in central-southern Chile.
GFAL: General Fishing and Aquaculture Law, SD: supreme decree, VMS: Vessel monitoring system
Periods Year Milestones
1991-2000 1991
1991
1992
2001-2012 2001
2001
2003
2004
2013-2023 2012
2013
2016
General Fishing and Aquaculture Law (GFAL 18.892 and 19.079)
Ratication of the National and Zonal Fisheries Councils
Creation of the artisanal shing register
Fishery declared as Fully Exploited Regime (SD 440)
Maximum catch limit per owner for individual quotas (GFAL 19.713) ending in 2012
Exclusive ve nautical miles from the coast for artisanal shers, southward of Valparaíso
administrative Region (GFAL 19.907 and 19.849)
Artisanal Fishing Register for individual quotas (GFAL 19.849)
Transferable Fishing Licenses for a renewable 20-year period, with a focus on sustainability,
individual catch quotas, and penalties for discarding, and rst nautical mile exclusive for
artisanal boats smaller than 12 m, certication of landings, and implementation of a satellite
surveillance VMS (GFAL 20.625)
Implementation of scientic-technical committees and management committees (Law 20.657
Management Plan for the common sardine and anchovy sheries
Marine and Fishery Sciences 39 (4): 501-523 (2026)
hoc
+ t
∈+
>
<
t
t+
t
>
Length-based indicator
==
=
==
th
th
>
=
==
+
Demographic traits
>
Monsalve Tequén et al.: Small pelagic fish demographic traits and fisheries management improvements
>
>
+
>
>
=× ≈
>
=× ≈
==+
= ≥
>
+M/k
+M/k
Kruskal-Wallis, p < 2.2e-16
1991-2000 2001-2012 2013-2023
Periods
Total length (cm)
20
15
10
5
2023
2021
2019
2017
2015
2013
2011
2009
2007
2005
2003
2001
1999
1997
1995
3579
11 13 15 17 19
Total length (cm)
Year
AB
1991-2000
2001-2012
2013-2023
Marine and Fishery Sciences 39 (4): 501-523 (2026)
post hoc
Modeling changes in GSI and CF
×
j1
=j1=
<
β==
β=
=
post hoc
< < <
< < <
Monsalve Tequén et al.: Small pelagic fish demographic traits and fisheries management improvements
<
<
<
β=
β=
6
4
2
A
J
Month
GSI
CF
0.90
0.85
0.80
0.75
FMAM JJASOND
B
J
Month
FMAM JJASOND
1991-2000
2001-2012
2013-2023
×+
+
+
M4 755,106.30 0 M3 + season × length interaction
×+
+
+
M4 -598,501.80 0 M3 + season × length interaction
Marine and Fishery Sciences 39 (4): 501-523 (2026)
510
C) GSI - length month interaction by period
1991-2000 2001-2012 2013-2023
J
Month
FMAM JJASOND
Length (cm)
10.0
12.5
15.0
GSI
10.0
7.5
5.0
2.5
JFMAMJ JASOND JFMAMJ JASOND
6
4
0
A) GSI seasonality by period
J
Month
GSI predicted
FMAM JJASOND
2
9
6
0
B) Length effect on GSI (month 8)
Length (cm)
GSI predicted
10.0 12.5
3
12
15.0
1991-2000 2001-2012 2013-2023
1991-2000 2001-2012 2013-2023
Monsalve Tequén et al.: Small pelagic fish demographic traits and fisheries management improvements 511
<
<
Spawning stock biomass and shing mortality
~
~
<
post hoc
<
=
>
+
=
=<
>=
=<
Length-based indicator
Marine and Fishery Sciences 39 (4): 501-523 (2026)
C) CF - length month interaction by period
1991-2000 2001-2012 2013-2023
J
Month
FMAM JJASOND
Length (cm)
10.0
12.5
15.0
CF
0.80
0.75
0.70
0.65
0.60
JFMAMJ JASOND JFMAMJ JASOND
A) CF seasonality by period
J
Month
CF predicted
FMAM JJASOND
0.8
0.7
0.6
B) Length effect on CF (month 1)
Length (cm)
CF predicted
10.0 12.5 15.0
0.85
0.80
0.75
0.70
0.65
0.60
1991-2000 2001-2012 2013-2023
1991-2000 2001-2012 2013-2023
Monsalve Tequén et al.: Small pelagic fish demographic traits and fisheries management improvements
600
400
200
0
1990 2000 2010 2020
C
Year
Recruitment (millions)
2,000
1,500
1,000
500
0
1990 2000 2010 2020
Year
SSB (tonnes)
1.00
0.75
0.50
0.25
0.00
1990 2000 2010 2020
Year
F (year )
-1
B
A
1991-2000
2001-2012
2013-2023
Marine and Fishery Sciences 39 (4): 501-523 (2026)
Trachurus murphyi
Engraulis
ringens
±
±
<>
1.0
0.5
0.0
-0.5
-1.0
A
Cross-correlation
rankSSB(t k) rankR(t)
-3 03
Lag
1.0
0.5
0.0
-0.5
-1.0
B
Cross-correlation
1991-2000
-3 03
Lag
1.0
0.5
0.0
-0.5
-1.0
C
Cross-correlation
2001-2012
-3 03
Lag
1.0
0.5
0.0
-0.5
-1.0
D
Cross-correlation
2013-2023
-3 03
Lag
Monsalve Tequén et al.: Small pelagic fish demographic traits and fisheries management improvements 515
>
<
L/L
max5% inf
L/L
95% inf
L/L
25% mat
L/L
c mat
P
mega
L
mean opt
/L
L
max,y opt
/L
L
mean F=M
/L
1.0
0.5
0.0
1.0
0.6
0.2
0.0
1.0
0.6
0.2
0.0
1995 2000 2005 2010 2015 2020
A
B
C
Marine and Fishery Sciences 39 (4): 501-523 (2026)
×
+
+
Monsalve Tequén et al.: Small pelagic fish demographic traits and fisheries management improvements
Declarations of use of AI
Conict of interest
Marine and Fishery Sciences 39 (4): 501-523 (2026)
Ethical approval
Author contributions
Strangomera bentincki
Engraulis ringens
Engraulis ringens
Sebastes melan-
ops
Sebastes melanops
Monsalve Tequén et al.: Small pelagic fish demographic traits and fisheries management improvements
Strangomera bentincki
Sardi-
nops sagaxEngraulis ringens
Strangomera bentincki
Engraulis ringens
É
Stran-
gomera bentincki Engraulis ringens
Stran-
gomera bentincki
Strangomera
bentincki
Stran-
gomera bentincki
Marine and Fishery Sciences 39 (4): 501-523 (2026)
Clupea harengus
Engraulis encra-
sicolus
Monsalve Tequén et al.: Small pelagic fish demographic traits and fisheries management improvements
Gadus morhua
Marine and Fishery Sciences 39 (4): 501-523 (2026)
Detailed implementation of generalized linear
mixed models
>
===
==
=
A=<==
==
==
×
μ=α+αp+fp+g+h
+pτ
ααp
fp
gh
bpτ
=
p=Σβ0π+
βs-
∈
β0βs
==
=
=
=
1 1
l1
=
f
+f
Monsalve Tequén et al.: Small pelagic fish demographic traits and fisheries management improvements
τ
j1
+
+×+
+
+=
+×
>
±≥
